" Portulacaria afra, the Elephant's Food or Spekboom:

a monograph which contains some of the areas of

both knowledge and ignorance pertaining to this plant"

© 1999-2012 by Robert J. Baran

Portulacaria afra


 

TABLE OF CONTENTS
PART I

TAXONOMY
ORIGIN
HISTORICAL REFERENCES
APPEARANCE
THE TRUNK
THE BRANCHES
THE LEAVES
THE FLOWERS AND FRUIT
THE ROOTS
VARIETIES

PART II
TEMPERAMENT
PROPAGATION
HORTICULTURAL & OTHER USES
CONTAINERIZED
BIBLIOGRAPHY

PART III
  THE OTHER PORTULACARIA
THE FALSE PORTULACARIA
BIBLIOGRAPHY



PART I



TAXONOMY

Kingdom: Plantae, generally, stationary organisms which contain the green pigment chlorophyll (which accomplishes photosynthesis, the manufacture of carbohydrates from carbon dioxide and water in the presence of light), and which can have fairly unlimited cellular regeneration;

Division: Magnoliaphyta (formerly Spermatophyta), plants which reproduce via seeds rather than spores;
Class: Magnoliopsida (formerly Angiospermae), at least 250,000 named species of true flowering plants whose ovules are enclosed in carpels [with fossil evidence since at least the early Cretaceous Period, 146 to 97 million years ago];
Subclass: Magnoliatae (formerly Dicotyledoneae), the dicots, at least 189,000 named species in 6 to 24 orders (depending on the classification method) of plants having two seed leaves, flower parts in 4's or 5's or multiples thereof, leaves not parallel-veined, and the plant increases in thickness by way of a cambium layer (which in woody plants produces annual rings);

O R

Division: Angiospermae, at least 250,000 named species of true flowering plants whose ovules are enclosed in carpels [with fossil evidence since at least the early Cretaceous Period, 146 to 97 million years ago];
Clade: Magnoliidae, primitive flowering plants whose pollen grains have a single pore;

Order: Caryophyllales, or Centrospermae, at least twenty-six families (Achatocarpaceae, Aizoaceae, Amaranthaceae, Ancistrocladaceae, Asteropeiaceae, Barbeuiaceae, Basellaceae, Cactaceae, Caryophyllaceae, Didiereaceae, Dioncophyllaceae, Droseraceae, Drosophyllaceae, Frankeniaceae, Giseckiaceae, Halophytaceae, Hectorellaceae, Limeaceae, Molluginaceae, Nepenthaceae, Nyctaginaceae, Physenaceae, Phytolaccaceae, Plumbaginaceae, Polygonaceae, Portulacaceae, Rhabdodendraceae, Sarcobataceae, Simmondsiaceae, Stegnospermataceae, Tamaricaceae).  Improved and unique investigative techniques on the genetic and molecular levels have been resulting in changing views of these relationships ), whose members include the cacti, carnations, bougainvillea, amaranth, sugar beet, pokeweed, and spinach.  This group alone has in the vacuoles of the cells the water-soluble betalain pigments of betacyanins (beet red-purple) and betaxanthins (yellow, orange, orange-red).  The flower ovary usually has free-central to basal placentation and the ovule integuments are twisted and bent.  [Fossils date from at least the Maastrichtian age of the late Cretaceous Period, about 74 to 65 million years ago, and possibly as early as the Albian, 111 to 104 million years ago.];

Family: Portulacaceae Juss., the mostly herb-like purslane family, with either 16 or 21 genera ( Amphipetalum, Anacampseros, Baitaria, Calandrinia, Calyptrotheca, Ceraria, Cistanthe, Claytonia, Grahamia, Lenzia, Lewisia, Lyallia, Montia, Portulaca, Portulacaria, Rumicastrum, Schreiteria, Silvaea, Talinella, Talinopsis, and Talinum ) having 580 named species, all with a tendency toward thick or fleshy leaves; the tropical members are shrubby, and the majority are annuals [with fossils distinct from their close Cactaceae relatives no later than the early Tertiary Period, about 60 million years ago] <older view>;

O R

Family: Didiereaceae Drake, the woody, succulent, often spiny didierea family, with seven genera ( Alluaudia, Alluaudiopsis, Decaryia, Didierea, plus Calyptrotheca, Ceraria, and Portulacaria ) having 19 named species found in Madagascar, South Africa and East Africa. <more recent view>;

Genus: Portulacaria Jacq., resembling purslane or pig weed ( Portulaca oleracea, L., a notoriously weedy trailing annual or perennial salad or pot herb);
Species: afra Jacq. 1787, from Africa, the tallest growing member of this family.  ( Anacampseros, Ceraria, and Talinum are the other Portulacaceae native to Africa. Portulaca is believed to be an import from Brazil during historical times.) 

Common: [Afrikaans:] Spekboom (lit., "fat pork tree"); [English:] Elephant's Food, Elephant Bush, Elephant Grass, Elephant-Plant, Olifantskos; Purslane Tree; Dwarf or Tiny Leaf Jade, Baby Jade [but RJB has also seen small rooted cuttings of Crassula offered as "Baby Jade" in the garden department of the Fountain, CO Lowe's, 11/31/08); gya-nese; [French:] pourpier en arbre; [German:] Speckbaum, Geldbaum, Pfennigbaum, Elefantenbaum, Strauchportulak, Jadebaum; [Portuguese:] albero dei lardo; [Ronga:] sala-ni-marumbi; [siSwati:] sidondwane; [Spanish:] Planta de la moneda; [Venda:] Tshilepwete; [Xhosa:] iGwanitsha (iGqwanitsha); [Zulu:] isAmbilane, inDibili-enkulu, isiDondwane, isiCococo, iNtelezi, iNdibili.

The common names derive from the succulent nature of the plant's leaves and stout trunk, and also from the observation that elephants will browse upon this.  It is said that in a feeding frenzy, the pachyderms will strip off all the leaves (and smaller branches) from this plant; but within a few weeks, the branches and trunks have begun to be covered again with a mantle of green.  In fact, it forms 80% of the elephants' diet in the Addo National Park (see below).  Each pachyderm consumes an average of 200 kg of food per day, but the plant is not "destroyed" as a result of this symbiotic relationship.  In feeding, the elephant breaks off the branches, eats the succulent leaves and then discards the larger branches, which re-root themselves.

First scientifically described by Nicolaus Joseph von Jacquin (1727-1817), an Austrian botanist and chemist, the most important of the younger contemporaries of Linneus (their correspondance began in 1759).  Jacquin was the first writer in German to utilize this new system of binomial nomenclature, and was foremost in his time with respect to the number of new species described precisely and in a consistent way.  He wrote at least ten major botanical works and a widely known textbook in general chemistry.  He visited the West Indies and South America (1754-1759), participating in the first scientific expeditions to Central America which were financed by the Imperial Court.  In 1768 he was appointed Professor of Botany and Chemistry and then became the second Director of the Botanical Gardens of the University of Vienna.  We have not found any evidence that Jacquin personally visited Africa. 

The plant known to us as P. afra was first illustrated from a rooted cutting in 1732 [some sources give the erroneous date of 1743] by Dr. Johann Jakob Dillenius, Oxford professor of botany, in his two-volume Hortus Elthamensis seu, plantarum rariorum quas in horto suo Elthami in Cantio coluit vir ornatissimus et praestantissimus Jacobus Sherard...Guilielmi P. M. frater, delineationes et descriptiones quarum historia vel plane non, vel imperfecte a rei herbariae scriptoribus tradita fuit (I. t. 101. f.120).   Not having flowered, it was understandably thought to be a species of Crassula.  Because of its ease of culture, it soon found its way into most of the famous gardens of Europe.  In a short 5 February 1771 letter to the Royal Swedish Academy of Sciences, Linneaus himself mentions that "Crassula Portulacaria har blommat i Italien; ar ett species af Claytonia" ("Crassula Portulacaria has blossomed in Italy, it is a species of Claytonia).  It is not known which Italian site had this honor.  Jacquin in 1786 [some sources give the erroneous date of 1789] published the first colored illustration of it, with flowers, in his Collectanea ad botanicam, chemiam, et historiam naturalem spectantia, cum figuris in Vienna (1:160-162, [b&w here] image on 406).  Therein he referred to it as an elegant shrub ("Elegantissima haec arbuscula").  Who brought the specimen(s) Jacquin classified and when?  One specimen -- presumably in a greenhouse -- is recorded as having flowered in Vienna in the year of the French Revolution (1789).  Was this the source of Jacquin's material?  How did it end up in Vienna and what happened to it?  Are there any plants alive today which can be traced back to cuttings from that tree?  (Jacquin also named 32 genera, 23 species within those, and 169 other species plus another 8 varieties or subspecies.  Monocots, dycots, and cycads were in his descriptions.  Possibly his two most widely recognized named specimens are Ulmus parvifolia Jacq., the Chinese Elm, and Zinnia elegans Jacq., the common zinnia.)

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ORIGIN

Data extracted from the National Herbarium, Pretoria (PRE), Computerised Information System (PRECIS)
as well as the Compton and Natal Herbaria.  (Map prepared by E.M.A. Steyn and G.F. Smith)
(Green dot is distribution of P. armiana, per Fig. 5 in Van Jaarsveld, 1984.)

From South Africa, where it grows, often in abundance in the drier parts of the Eastern Province -- especially on the high plateau Karoo hill slopes or flats (c. 400 to 1,060 meters above sea level) -- and is particularly prominent in the Addo bush to the south where there is tremendous summer heat. 

The Addo Elephant National Park is situated in the Eastern Cape Province 72 km by road from Port Elizabeth.  Proclaimed in 1931 to save the last 11 survivors of the once numerous Eastern Cape elephants, the park consists of 12,126 hectares -- 30,315 acres -- of gently undulating Valley Bushveld dominated mostly by the Spekboom, which covers approximately 80% of the park area.  Some 500 species of plants are to be found in the park.  Elephants eat P. afra from the top downwards allowing the plant to spread itself vegetatively by spreading horizontal branches at ground level.  Outside the park the same plants are eaten by goats who eat the plant from ground level upwards preventing the plant from spreading vegetatively.  Consequently these plants must rely solely on seed to proliferate the species which often proves difficult in such a dry climate.  As a result it was observed that inside the park where the plant is subjected to browsing by elephants, Portulacaria afra survives and spreads successfully, whereas outside the park the plant is becoming sparse as a result of overgrazing and poor regeneration.

The Spekboom Succulent Thicket (aka Spekboomveld) is an area of some 5,011 sq.km., 1.76% of which is conserved in some reserves such as at Graaff Reinet and on higher altitude slopes.  The steep mountain slopes in the Eastern Cape and the eastern parts of the Western Cape receive perhaps 250 to 300 mm of rainfall per year, mainly in the autumn and spring.  Temperatures are moderate, although extremes may be experienced for short periods.  The thicket occurs on sandstone, quartzitic and shale substrata, which gives rise to shallow soils.  Spekboom can form pure stands, but usually dominates a dense scrub which includes woody shrubs, succulent herbs and grasses.

Very common in some places, though much more so in days past before overgrazing almost exterminated it in some areas.

It occurs on the eastern areas of the country from the Eastern Cape northwards into KwaZulu-Natal, Swaziland, Mpumalanga and the Northern Province in rocky areas of dry succulent karoo scrub, thicket and bushveld.  It also occurs in dry hot river valleys of the eastern Transvaal, through Swaziland and north into Mozambique an uncertain distance. 

The Spekboom River, in the Lydenburg district, is named for the plant and not vice versa.

When was the plant first discovered by Europeans and given its common names?  When was it first brought to Europe and North America?

It is not known what the nearest fossil relative was.  It is not known if there have been any botanical "cousins" which have become extinct contemporary to neighboring indigenous human populations.  It is not known what the largest pre-historical dispersion of P. afra was.  It is not known what any of the local myths are regarding the origin of this plant.   (The truly native human population of the area is a Stone-Age culture dating back some 20,000 years.)

It is not known how old the current most senior specimen of this plant is or where that is located.  A photo from early 2011 shows Jim Smith trimming a specimen that is alleged to be 300 years old, per a caption from its Facebook circulation.  In truth, "[I]t started its training [emphasis added] in 1978 when it was collected from an urban garden in Vero Beach, FL.  At that time the trunk was only about 2" wide."  Thus, the tree was in training for 32 years.

The tree shown at the top of this page was in training from at least 1983-2007 (24 years), with an estimated final age for the plant being about 55 years.

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HISTORICAL REFERENCES

P. afra has a long garden history in South Africa, and was introduced into Dutch and English gardens more than two centuries ago.  (The Dutch founded Cape Town at Table Bay on the southwestern tip of the continent in 1652.  The first large-scale British settlement was established in 1820 some 900 km away to the northeast and 40 km inland in the eastern coastal region at a place which was the garrison of Fort Graham and would be eventually called Grahamstown.  Less than 50 km to the southwest of that site is the aforementioned Addo bush.)


1823 - "PORTULACA'RIA (Bot.) a genus of plants, Class 5 Pentandria, Order 3 Trigynia.
Generic Character.  CAL. perianth two-leaved; leaflets roundish, ovate. -- COR. petals five, obovate. -- STAM. filaments five, awl-shaped; anthers erect. -- PIST. germ three-cornered, superior; style none; stigmas three. -- PER. none; seeds single.
Species.  The single species is the Portulacaria afra, Claytonia, Crassula, seu Anacampseros."
Crabb, George  Universal technological dictionary or familiar explanation of the terms used in all arts and sciences:containing definitions drawn from the original writers : in two volumes (London: Baldwin, Cradock & Joy; Volume 2; pg. POR)

1834 - "The spekboom, with its light green leaves and lilac blossoms."
Pringle, Thomas  African Sketches (vi. 209)
"Browsing on the succulent spekboom, which clothed the skirts of the hills."
Ibid. (vii. 248)

1841 - "But there was on the hills a considerable quantity of spek-boom, (i.e. fat-tree,) a shrub with succulent leaves, slightly acid, which supply both food and moisture to the horned cattle. "
Extracts from the Letters of James Backhouse: Whilst Engaged in a Religious Visit to Van Diemen's Land, New South Wales, and South Africa, Accompanied by George Washington Walker (London: Harvey and Darton, Vol. II; pg. 24)

1843 - "One of the most valuable shrubs...is the spek-boom (portulacaria afra).  It is found in great abundance on the stony ridges and affords excellent food for those large flocks of sheep, and especially of goats...  In severe droughts this bush is truly invaluable."
Cape of Good Hope Almanac

1844 - "Before reaching the Roodeberg [Hoek Fontein, Red-mountain-corner Fountain], which is Red Sandstone, enclosing boulders, a man who had accompanied us from our lodging-place, left us: he took another of the many roads which cross this desert country in various directions, to farms situated wherever a little water / is to be found. -- Between this place and the foot of the Zwartebergen, Black Mountains, we came at no water, and the day was intensely hot; but on the hills there was a considerable quantity of Portulacaria afra, or Spek-boom, Fat-tree, a shrub with succulent leaves that are slightly acid, which supply both food and moisture to the horned cattle."
Backhouse, James  A Narrative of a Visit to the Mauritius and South Africa (London: Hamilton, Adams; 1844, Vol 2, pp. 113-114)

1850 - "One vast jungle of dwarfish evergreen shrubs and bushes, amongst which the speckboom was predominant."
Cumming, R.G.  A Hunter's Life in South Africa (1902) 12/1

1852 - "The eastern zone [of the cone-shaped mass of land which constitutes the promontory of the Cape] is often furnished with mountains, well wooded with evergreen succulent trees, on which neither fire nor droughts can have the smallest effect ('Strelitzia', 'Zamia horrida', 'Portulacaria afra', 'Schotia speciosa', 'Euphorbias', and 'Aloes arborescens'); and its seaboard gorges are clad with gigantic timber."
Livingstone, David  Missionary Travels (1857; Chapter 5)

1877 - "The Portulacaria Afra is the 'Spekboom' of the Cape of Good Hope, said to be the favourite food of the elephant.  It is one of the numerous forms which confer a peculiar physiognomy on the vegetation of the Colony: --
     "The strange, stiff, gaunt forms of the leafless, which suggest the idea of some monstrous Indian idols; the Aloes, with their spear-like leaves and tall scarlet spikes; the pale-green foliage of the Spekboom; the Crassulas, covered with milk-white blossoms; Cotyledon, with its bluish leaves and bright red flowers, form a combination extremely interesting, which must strike every traveller of ordinary habits of observation, by its dissimilarity to anything that is seen in other countries.  There cannot indeed be a vegetation more peculiar or of a more marked character."
Allnutt, Henry  The Cactus and Other Tropical Succulents (London: Estates Gazette Office; pg. 46).

1877 - "The hills are clothed with spekboom and other nourishing trees and shrubs."
Brown, John Croumbie  Water Supply of South Africa, and Facilities for the Storage of It (Oliver & Boyd; pg. 479).

1878/9 - "C'est le pays des Mesembrianthemum, des Crassulacées, Stapéliées, Aloïnées, Euphorbiacées ; on y trouve aussi des Composées, Asclépiadées, Apocynées; un Ipomoea pourvu d'une immense tige souterraine subéreuse, et la Portulacaria afra ou Spek-boom, buisson étrange à feuilles charnues et acides."
("It is the country of Mesembrianthemum, Crassulaceae, Stapeliae, Aloes, Euphorbiaceae; there are also Compositae, Asclepiadaceae, Apocynaceae; a corky morning glory equipped with a vast underground stem, and Portulacaria afra or Spek-boom, a strange bush with acid and fleshy leaves.")
(Bulletin de la Société botanique de France, vol. 26, January-June 1879, pg. 22, from review of Distribution of South African Plants by M. Harry Bolus in The Cape Argus, 5 Novembre 1878).

1879 - "The spek-boom, from which the river takes its name, grows here in great profusion."
Atcherley, Rowland J.  A Trip to Boerland (pg. 186).

1880 - "Portulacaria Afra, Jacquin.
South Africa.  Called Spekboorn [sic].  Affords the principal food for elephants; thus this succulent shrub may deserve naturalisation on stony ridges and in sandy desert land, as likely nourishing to sheep."
von Mueller, Ferdinand  Select extra-tropical plants readily eligible for industrial culture or naturalisation: with indications of their native countries and some of their uses (Off. of the superintendent of government printing; pg. 257).

1891 - "The spekboom, which is a good-sized shrub, sometimes attaining the height of fifteen or twenty feet, grows plentifully a little way up the mountains; and in very protracted droughts, when the karroo and other bush of the plains begin at last to fail, it is our great resource for the ostriches, which then ascend for the purpose of feeding on it; and though they do not care for it as they do for their usual kinds of food, it is good and nourishing for them.  Elephants are very fond of the spekboom, but though a few of these animals are still found near Port Elizabeth, there are fortunately none in our neighbourhood to make inroads on the supplies reserved for the ostriches against what certainly in South Africa cannot be called "a rainy day."  The spekboom has a large soft stem, very thick, round, succulent leaves, and its clusters of star-shaped, wax-like flowers are white, sometimes slightly tinged with pink."
Martin, Annie  Home Life on an Ostrich Farm (New York: D. Appleton and Company; pg. 51).

1893 - "...The gaunt leafless Euphorbia; the Aloe, with its spear-like leaves and tall scarlet spikes; the spiny palm-like Zamia; the Spekboom, with its pale green foliage and bright blossoms; the elephant's foot, the Strilitzia, the ivy-geranium, the Plumbago, and numerous other shrubs and flowering plants, make their appearance, whose strange and peculiar forms at once strike the eye..."
Noble, John (ed.)  Illustrated Official Handbook of the Cape and South Africa: A Résumé of the History, Conditions, Populations, Productions, and Resources of the several Colonies, States, and Territories  (First published under the title: Official handbook.  History, productions, and resources of the Cape of Good Hope) (Cape Town & Johannesburg: J.C. Juta & Co.; pg. 18).

1893 - "As we got lower down the valley, there were masses of spekboom (Portulacaria afra) with thick swollen stems and branches (like gutta-percha tubing badly put together), covered with small green fleshy leaves and tiny pink flowers.  It is the pet food of elephants."
North, Marianne  Recollections of a Happy Life (Chapter XIV)
"The railway took me through the Addo Bush: a flat, swampy locality, full of spekboom trees, which are said to tempt the elephants down close to civilization, and herds of them are still found there."
Ibid.

1895 - "The Cape Gardens have hitherto had little to do with the introduction and distribution of economic plants or the dissemination of information respecting such subjects for the use of the general community.  What has been attempted in this direction was owing entirely to the personal efforts of the curators.  The following extract from Professor MacOwan's Report for 1883, pp. 3-4, shows how much more might have been accomplished if the funds at his command had allowed:
     "The garden has been able to supply many demands made upon it by similar institutions at home and abroad and numerous private collectors, for things scarcely in the usual run of trade supply, partly gratis and partly by sale...  Several enterprising cultivators are now, at our suggestion, trying to multiply the thornless Opuntia and the spek-boom in Namaqualand, Angra Pequena, and elsewhere.  I think these excellent food plants have not received the attention they deserve.  Of course they are special food plants, suited to special localities, and do not come into competition with the ordinary veldt-bosjes and grass wherever the climatic conditions permit the usual pasturage.  But I am sure that should the spek-boom be incapable of acclimatisation on the sun-smitten randts of Namaqualand, the Opuntia may be grown in vast thickets at the junction of rock and sand veldt, and its use would save much of the present expenditure in importing compressed hay for trek-cattle.  Such culture throughout all karroid districts of the Colony subject to frequent failure of seasonable rains is far more important than the introduction of any more of the fancy staples which are from time to time proposed, praised, and forgotten, and which have given point to the proverbial sneer that 'the Cape is a country of samples.'  I wish it could be added that these supplies and others to the Government Forest Department were all made gratis.")
Royal Botanic Gardens, Kew, JSTOR (Organization)  Kew Bulletin of Miscellaneous Information, March 1895, No. 99 (London: H.M. Stationery Office; pg. 50).

1896 - "Spek-boom, Portulacaria afra, Jacq., is a fleshy, rounded-leaved, scrubby, soft-wooded tree or bush, which is recognised as a very valuable food plant for sheep, cattle, and even horses.  Successful efforts have been made to grow it in Namaqualand from cuttings.  As these are liable to rot when put in green and newly severed, they should be spread out for a fortnight to allow the wounds to dry.  Where animals are well fed and pampered, they sometimes lose taste for this excellent natural food.  In the neighbourhood of Oudtshoorn, on a farm where, in the spring of 1895, ostriches were dying in hundreds, clumps of spek-boom were within easy reach, but the birds would not touch it, having been accustomed to feed on lucerne.  Nevertheless, when birds are brought up to eat it they thrive well, and seem fond of it.  The spek-boom is a bush which recovers rapidly from the injury done by too close browsing by stock, if a season's respite be granted to it.  When spek-boom and the Mesembrianthemum floribundum are present, stock care but little about their daily visits to the water-vlei."
Wallace, Robert  Farming Industries of Cape Colony (London: P.S. King and Son; Cape Town: J.C. Juta and Co.; pg. 88)

1899 - (following the scientific description is this:)  "Drawn and described from specimens in flower on Berea [a ridge above the northwest side of Durban], October, 1989.
     "The genus Portulacaria includes two species only, the one here described which is also found in some parts of the Cape Colony, and P. namaquensis, which, as the name implies, is a native of Namaqualand.  P. afra has, we understand, been exported to Algeria [on the north end of the African continent, some 4100 miles or 6700 km away], and Australia [approx. 6300 miles or 10,200 km away] as a browsing plant for cattle and sheep, and is said also to be a valuable food for ostriches, but it does not seem to find much favour for cattle feeding in Natal.  The leaves are sour, and have been used for culniary purposes.  It is known to the Dutch colonists as 'Spekboom' and to Natal colonists as 'Elephant food.'
     "Fig. 1, Branch with leaves and flowers, natural size ; 2, Flower and buds in situ ; 3, Section of flower ; 4, Stamen ; 5, Calyx, ovary and stigmas ; all enlarged."

Portulacaria afra, 1899 in Wood and Evans' Natal Plants, Plate 78
(Plate 78 from pg. 239, drawn by Walter Haygarth, "a Natal born colonist,"
reproduced here smaller than size in book.)

Wood, J. Medley, A.L.S. and Evans, Maurice S., M.L.A., F.Z.S.  Natal Plants, Vol. 1 (Durban: Bennett & Davis; text on pp. 163-164.)

1907 - "The surrounding pastoral country is usually covered with good grazing grass, and the edible bush, the native spekboom, is frequently met with in the kloofs."  (Under "Queenstown")
Burton, Alfred Richard Edward  Cape Colony To-day (Cape Town: Townshend, Taylor &Snashall; pg. 209).

1908 - "...in the primary cortex of Portulacaria afra, Jacq. [leaves], the green cells form a network between the large, colourless cells."
Solereder, Hans and Dukinfield Henry Scott  Systematic anatomy of the dicotyledons: a handbook for laboratories of pure and applied botany, Volume 1 (Clarendon Press; pg. 111);
"Oxalate of lime occurs in three forms, as clustered crystals, as solitary crystals (which, according to Becker, belong to the tetragonal system), and as crystal-sand.  In the leaf, Becker observed clustered crystals alone in Calyptridium, Lewisia, Monocosmia, Portulaca, Portulacaria, and Talinum, clustered crystals and solitary crystals in Anacampseros and Spraguea, and a peculiar crystal-sand, consisting, according to my own investigation, of small needles and small prismatic crystals, in Calandrinia.  At the same time it may be added, that in the stem oxalate of lime is met with in the form of clustered crystals.  Claytonia and Montia have no deposits of oxalate of lime either in leaf or stem.  Of internal secretory elements, mucilage-cells alone occur in the Order [of Portulacaceae [sic]].  These take part in the storage of water, and, among the genera investigated by Becker, are wanting only in Montia and Claytonia.  They are met with in the leaf-tissue as well as in the ground-tissue of the stem, and are sometimes (Anacampseros and Portulacaria) of considerable size.  The contents of, the mucilage-cells in question are membrane-mucilage, according to Walliczek; further detailed investigations regarding this point are, however, desirable.  In view of such investigations it may be remarked that, according to Becker, the mucilage-cells arise very early..."
Ibid (pg. 112).
"In Portulacaria afra, Jacq., the vascular bundles are separated from one another by broad unlignified medullary rays; the xylem of the former consists of wood-prosenchyma with simple pits and of tangential bands of unlignified thin-walled cells, including pitted vessels, which have delicate spiral or reticulate thickenings."
Ibid (pg. 113).

1913 - " Portulacaria afra (the spekboom) grows socially in the southeastern Karoo, extending right through to Kingwilliamstown; it is also reported from the Eastern Transvaal.  It often covers whole hills or mountain slopes with its fresh verdure, which forms a pleasant contrast to the surrounding dull coloured vegetation.  In the Addobush it is arborescent, up to 20 feet high, often forming dense thickets.  The juicy leaves are a wholesome food for all classes of stock as well as for wild animals including buffaloes and elephants; hence farms with plenty of spekboom need not fear an ordinary drought.  'Providence meant to spoil our farmers in placing the spekboom on the hills of the Karoo,' wrote MacOwan in one of his articles on the fodder plants of the country."
Marloth, Rudolf   The flora of South Africa (vol. 1)



"South Africans have a saying: as long as your Spekboom (Elephant Bush) grows and prospers, so will your finances."
(Per "Variegated Elephant Shrub," http://www.sunnygardens.com/garden_plants/portulacaria/portulacaria_2367.php, but RJB has NOT yet confirmed this elsewheres.  The sunnygardens page with this quote dates at least to 26 Jun 2006.  As time goes by, additional web pages about dwarf jade plants have been including this quote -- which still hasn't been tracked down previous to sunnygardens.)

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APPEARANCE

Similar in appearance to the Jade Plant ( Crassula argentea or C. arborea, family Crassulaceae, order Rosales or Saxifragales ), P. afra has smaller and rounder pads and more compact growth (shorter internodal spaces, down to even 1.5 mm).  It is much hardier, faster growing, more loosely branched, and has more limber tapering branches than Crassula.  P. afra is sometimes still sold as Crassula portulacaria, its original designation.

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THE TRUNK

This is a stout juicy-stemmed, soft-wooded, semi-evergreen upright shrub or small tree, usually 2.5 to 4.5 or more meters tall.  The diameter of the trunk can be 20 cm or more.  The life expectancy of the plant, while demonstrated to be over 50 years, is unknown.  The specific gravity of the wood is not known.  The annual rings are somewhat visible in cross sections of the wood.  The greyish or reddish outer layer of the bark becomes very wrinkled with age, perpendicular to the trunk's axis. 

Observed in a container plant setting, the near-paper-thin outer bark can be completely removed in a ring from around the mature tree without harm.  On older specimens the bark can partially dry out and flake off by itself.  At least one equally thin layer would have already formed underneath. 

The tallest non-dug specimen is unknown.  The trunk with the largest girth is unrecorded.  There is a story told of a very large landscape specimen in Florida having a trunk over 30 cm in diameter.  This P. afra was worked on at the owner's request c.1960s or 1970s by landscaper and bonsai master John Y. Naka who was visiting the area for a workshop.  Requiring a saw to cut through the tough wood, John worked on the tree for quite some time, cutting it back severely and shaping it to fit the garden in which it grew.  (Per sensei Leroy Fujii to some members of the Phoenix Bonsai Society one evening during a meeting break at the Valley Garden Center entrance, c.1990.)

It is not known what the largest area is that is covered by one plant or by a tangled thicket of the plants.  An unsourced article gives the maximum width -- but also, very erroneously, the heighth! -- as 15.00 metres / 48.75 feet.

P. afra and Ceraria namaquensis (the wolftoon) are the only members of the Portulacaceae family which grow to tree size.  (All of the species of the Didiereaceae family reach over 3 m tall; the two Alluaudia species are said to reach up to 12-15 m in height.)

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THE BRANCHES

The leaves and young branches /branch tips are quite phototropic.  Older branches, gray, shiny and up to 5 cm thick, will hang down or trail on the ground.  Spreading outward, less frequently they will grow erect, especially at the center of the plant.  There is some evidence that erect branches -- to at least one meter in length and often with secondary branches extending outward at a 45 degree angle from the main branch -- thicken more quickly than trailing branches do even when the latter are feeding a greater number of secondary branches.  Unpruned branch tips are the same color as the leaves; branches gradually turn reddish and then the reddish-brown, plum-red or dusty mottled brown of lignified maturity. 

The underside of a branch tip will remain green or at least have a greenish tinge for a while after the top side has turned red or reddish-brown.  The lowest point of a hanging branch which has an upturned tip will have the most green remaining.  While the cover of a leaf above may help keep the branch portion directly underneath it from turning reddish more quickly, late green below a node has also been seen on the side where a leaf has been missing for some time. 

The cylindrical articulate branches break very easily.  The top thin layer of bark on lignified branches more than a few years old begins to crack and can peel/flake off unevenly, primarily internodally.  Drought stress during the summer may play a role in this.  Secondary and tertiary branches appear to have shorter internodes than primaries.  The longest continuous branch (as opposed to a ramified branch) is unrecorded, but anecdotal evidence indicates it easily can be over three meters.  New buds and shoots can continually arise along the trunk and branches, and even from the junction of a larger branch and the trunk.  This results in multiple diameter and aged branches along a given section of the tree.  The branches eventually form a thick network with the bottom most branches being leafless.  Branches slightly more exposed to sunlight will hold on to larger pale green or yellowed leaves.  Thin inner branches may only have leaf pads at their growing tips.  A branch broken at its juncture can continue to grow and thrive if the break occurs on the upper half of the juncture and if, obviously, the branch has not been entirely separated from the trunk or larger branch from which it arose.

A lateral section (i.e., a long shallow "divot") of a branch can be removed down to the core up to 1/3 diameter without major injury to the branch or plant.  The wound will heal slowly.  New buds have been observed growing at the base of one such wound at an internode junction.  The next node above had been removed by the wound and thus did not bud out on that side of the branch. 

On dead branches and dead above ground roots, the inner wood of dark brown shrinks by about 1/3 to 1/2 diameter (lateral shrinkage is much less), leaving the thin two-layer slightly wrinkled dusty-brown bark to flake off in internodal segments.  The inner bark layer is lighter brown in color. The dark brown inner wood breaks off in flakes/powder.  Underneath it is a light brown wood made up of long continuous (not just internodal) fibers.  Within that is a dark-brown hard powdery core.  In older specimens, the inner layer of the trunk bark can be 2 mm thick.

Limited tests with a handheld butane lighter on completely dead branches 1 to 1.5 cm in diameter have shown that the dry bark is mildly flammable.  The resulting flame, however, went no further than 4 cm along the sides of the branch held in either a vertical or horizontal position before self-extinguishing.  Only the outer layer of bark seems to burn most of the time.  The inner bark burns if the charred bark is stripped from the branch and re-ignited.  As for the inner wood, other than taking on a black or dark brown slightly shiny finish, the wood does not ignite or appreciably smolder.  Prolonged exposure to flame charcoalizes the wood.  Removal of the charcoal down to the central fibrous mass uncovers material that will ash white and ember, smoldering but not igniting.  Blowing on the embers does not produce flame but does speed up the decomposition, however, only for the duration of the extra ventilation.  Brief fire may not do much damage to or be fueled by deadwood underbrush.  Larger, hotter flames, possibly with mechanical turning of the charred branches, could be dangerous.  The smoke released appears typical of burned wood, with very fine ash particles and no distinctly pungent aroma.  Its composition is unanalyzed.

A knife cut made along the length of a stem across one or more nodes may result in a bud arising from one or more of those nodes at the site of the cut.

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THE LEAVES

Has opposite, obovate (egg-shaped), glabrous, very fleshy, blunt green leaves usually less than 1.3 cm long and without a distinct petiole or leaf stem.  Less common are some old leaves which can reach at least 2.8 cm in length, up to 2.3 cm in width, and can be rounded, tear-drop, or triangular in shape.  These largest leaves sometimes show a rudimentary petiole 2.5 mm wide at the branch juncture and up to 2 mm long into the leaf.  If there is a petiole present, it curves slightly towards the bottomside of the leaf.

New leaves arise approximately 90 degrees to the previous pair and are lighter green in color.  A very limited number of previous pair leaves have been seen to be extremely stunted, barely developed, while their successors usually fully develop without any signs of retardation in these younger pads or their successors.

The middle of the outer edge of young leaves shows a tiny pointed apex.  Sometimes there is a thin faint reddish edge on younger leaves.  A faint and sometimes unnoticeable cleft runs down the center of the leaf from the base to the outer tip.  This feature occasionally results in heart-shaped leaves having the center of the apex drawn in.  Once a green leaf has this shape it will not revert to obovate, and vice versa.

Without visible external veins, the leaves appear to be covered with a fine grain pattern of pores on both sides.  The largest leaves may have a secondary, less distinct but larger pore pattern which overlays the leaf surface top and bottom.  The pores appear to be up to ten or so per square millimeter, arranged in a not random fashion.  Definitely not in columns and rows, they are not quite as patterned as the pores in the whorls of a fingerprint.  Growing conditions can make the leaves shiny with the appearance of being barely dusted with silver.  A thin transparent layer covers both the top and bottom of each leaf.  Gentle pressure from a thumbnail on the underside of a leaf will "blank" out the pores; relatively greater pressure is needed to do this to the upper surface.  The effect of this action on a still-attached leaf is unknown.  Half of the underside can be "blanked" in this way without the attached leaf showing any ill effect.

On a limited number of upright growing branches it has been observed that the leaf pairs are rotated slightly more than 90 degrees from the one directly under them.  A gentle counterclockwise spiral is formed so that, within an upward length of about 30 cm, the leaf pairs are 90 degrees to the right of the corresponding alternating pair five levels below.

Removal of a large older leaf along an unbranched segment will stimulate a pair of new leaves to break at that node, and thus the start of branching from that point.

The leaves turn yellowish and slightly more pulpy when old or if the plant is stressed, separating then very easily from the branch.  Drops of moisture can actually be squeezed out of the yellow pulpy leaves using one's fingers, but the composition of the liquid is unanalysed.  Some leaves will turn blackish and become desiccated, also separating freely from the branch.  Fresh picked green leaves also can be finger-crushed to release their cellular fluids.  The first leaf so crushed releases a barely slick clear liquid which foams slightly after rubbing thumb and forefinger together.  Subsequent leaves crushed by the same fingers release liquid which foams more quickly with less mechanical agitation.  The uninjured plants have no noticeably distinct scent to humans.  The moisture in leaves split open is non-allergenic.

The average life expectancy of the leaves is at least one year, but otherwise unrecorded.  Some leaves, usually older/larger ones, may leave their central vein if not cleanly removed from the branch, i.e., if they are pinched off with fingers rather than snipped off with shears.  The whitish vein, a few times thicker than a human hair, begins at the leaf base.  With a width of up to 1 mm across there, it lies just above the bottom interior of the leaf base and could be located off visual center of the juncture.  Inside the leaf, the vein splits into at least two strands before it reaches the blunt end of the pad.

It is not known if complete defoliation would result in smaller new leaves, or if this technique would be of any harm to the plant.  Correspondant Susan Marsh (4 Feb 2011) tells us that, from her experience "if the plant was already healthy and the weather is warm (i.e. summer), defoliation just causes a whole bunch of buds to appear.  The new leaf size can be semi controlled by how much water you give the [dwarf] jade once the leaves grow (you only water when the soil dries pretty much completely after you defoliate until then).  If you water sparingly the new leaves will stay smaller.  The more you cut/pinch the smaller the new leaves are."

Injuries to trailing branches and leaves, e.g. from foot traffic, appears as semi-crushed or abraided tissue.  Uninjured buds beyond the injury usually will grow normally.  Limited tests show that when subject to a butane lighter's flame the thin outer layer of fresh picked green leaves blackens and wrinkles, tearing very easily at the touch of a finger.  The moist pulp underneath is olive in color and partially decomposed.

Some leaves have been observed to turn pulpy and die after exposure for only one night to air temperatures not more than 10 degrees F below freezing.  The percentage of leaves thus affected and the length of duration and temperature for this to occur is not specifically known.  Frost-damaged branches have purplish-brown pads which then shrivel dessicated.  The stems fade slightly from the natural reddish-marroon tone.  Very limited experience with frost-touched but porch-sheltered container plants shows no appreciable pattern: affected branchlets were not neighboring, were not even of equivalent heighth above the ground or distance away from open air, were not seemingly of any particular character worse or better than the unaffected branchlets next to them.

Leaves large in length have been measured up to 3.5 mm in thickness.  (A slight curve to the overall leaf gives a maximum apparent thickness of 4 mm.)  A cross section of a leaf shows two portions: the top side is one third to forty percent of the thickness of the pad.  The two portions are divided by a slightly darker very thin strip.  Using a handheld lens, one can observe this strip in sections of < 1 mm thick leaves (corresponding length and width of a fat tear-drop shaped sample pad was 5 mm x 5 mm).  Where the top and bottom meet along the exterior leaf edge is the tiny margin, perhaps .1 mm in width.  On older leaves portions of this sliver can show a whitish or brown dried callus, which may be due to exposure to the elements.  The leaf in cross section shows the grain as uniformly flowing from top to bottom.  Slices of leaves have the color and texture of cut green beans, with perhaps a similar but much fainter scent.

Several mature containerized specimens, of various parental stock, which were brought indoors for the winter and positioned two to four meters away from an east-facing window produced a number of uncharacteristic leaves as new growth: relatively thin but slightly curled, very phototrophic.   One 35 cm shoot from a mature trunk base had a partially lignified bottom half at age 6 months, sited four meters from the window.  The thinness of these pale light green new leaves was most remarkable.

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THE FLOWERS AND FRUIT

The flowers are pink/rose/lilac-colored, 2 to 2.5 mm long and short-pedicelled.  They are clustered in the upper leaf axil, the point at which the stalk or branch diverge from the stem or axis to which it is attached.  The flower is panicled, that is, with a loose, open flower cluster, approximately 5 to 7.5 cm in length, which blooms from the center or bottom toward plant is never terminated by a flower.  The bisexual flower has two conspicuous persistent sepals which are papery but become stiff, five persistent petals, four to seven stamens, a four or five lobed short corolla tube, and a three-angled superior one-chambered ovary, angles winged and deeply tinged with red, with three stigmas, sessile, spreading, densely muricate above, white.  (A microphotograph of Portulacea afra [sic] pollen grains can be found here.)

In South Africa P. afra bears these star-shaped flowers in late spring and summer after the rains, but seldom blooms in the western U.S., Hawaii, or Florida.  The flowers are rare in cultivation, but if kept very dry the older [and presumably unpruned] plants may flower after rain.

In 1947 it was "reported that in the vicinity of San Diego, flowering frequently occurs in October and November, following the first rains, and is especially likely in old plants that have been completely dry for several months."   A couple who had plants in Solana Beach were said to "water their plants about twice a month, and the plants flower regularly every summer."

There is at least one recent documented exception to the flowering-when-very-dry observation.




In a good flowering season for Portulacaria, in areas such as the Fish River Valley, north of Grahamstown, the scenery is enveloped in a pink haze, because of the great abundance of its small flowers.

Bees will swarm a blooming tree and the resulting honey is described as good.

It is not known how old or large a plant must be in order to first flower.

The berry-like fruit is pinkish, small, light, dry, indehiscent, transparent, about 5 mm long, 3-winged, 1-seeded, scarcely or tardily splitting.  Usually borne in abundance in drooping catkins, the seeds give the tree the appearance of a second flowering from August to September.

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THE ROOTS

As observed in a container setting, a transplanted specimen rapidly forms a fine network of feeder roots which are brittle and delicate for several weeks.  Extensive tests on seasonal root growth patterns have not yet been conducted.  Roots have a reddish outer layer around a white core.  In the wild, the primary roots are described as being thick, seamed, smooth, grey or ruby-red.

In cuttings set in water, the resulting white cluster of  roots reaches about 10 mm in length before the cutting starts to rot after about one month.

It is not known how deep or how wide the roots of a landscape or wild specimen can reach.  It is not known what the largest diameter root is -- or if the plant produces the equivalent of a tap root.  It is not known what portion of a plant's total mass the root ball is.  It is not known if there is any symbiotic relationship between the roots of P. afra and one or more species of fungus or other lifeforms.  It is not known if chemicals produced by the roots (or any symbiot) increases or decreases the growth of other plants nearby.

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VARIETIES

There are at least five green forms ("macrophylla" has larger leaves, 2.5+ cm long and 1.7+ cm wide and is aka "Limpopo" representing the northern populations which extend into the northern provinces of South Africa and Mozambique, while "microphylla" has smaller ones, .6 cm long and wide), and these five named variegates:

"Aurea" is a form (new by the early-1960s) having a reddish stem, small light green leaves featuring a yellow center, flushed with pink beneath. 

"Foliis Variegatis" is a form (dating at least from the early-1950s) with leaves variegated or mottled yellow.  It has been sold under the name "Rainbow Bush."

"Gold" has its new leaves emerging completely golden ochre before they fade to bright lime.

"Variegata" (from at least the early-1960s, it also has been sold under the name "Rainbow Bush" and is, additionally, known as "Tricolor") has leaves with distinct tiny carmine-red or purplish-pink margins or edges on pale whitish-green or milky-green leaves with pale green centers and margined creamy-white.  There is more green on the undersides of the leaves, often with an appearance of the color having been brushed onto the leaf.  The red margin is most distinct on new buds, making up almost all of its coloring.  (New buds on the green varieties have much less red margin.)  The red might fade a bit with maturity, or deepen red on the same plant.  During the cool of winter the red on the margins intensifies and appears to enlargen slightly.  During the growing season, branch tips which are pale greenish-red turn to reddish-brown sooner than they would on the green varieties.  Old age, insufficient watering, or longterm full sun exposure on this variety shows itself with browned withering of part of the leaf edges and fading of the green in the center as the leaves turn yellowish-white.  The leaves curl lengthwise slightly before darkening.  Such leaves when dropped might still show a slight red margin and a hint of green although semi-opaque.

"Medio-picta" has green leaves with whitish markings spreading from the centre and bright red stems.

Variegated forms are slower growing and smaller than the green varieties of the species.  It is not known where, when or by whom the varieties were first discovered.  It is not known where the largest stand of any of the varieties can be found, either growing in the ground or containerized.


A prostrate form has been brought to RJB's attention by Allen Repashy of http://www.xericworld.com/forums/ in personal e-mails 09, 23, and 25 Nov 2008.  "Gary Hammer is a famous plantsman and world traveler from California who has introduced quite a few plants to horticulture.  I have no idea how long ago he came up with [the prostrate variety]...  It grows like a mat about three or four inches off the ground.  John Trager at the Huntington Botanical Gardens also thought that was where theirs came from.  I don't think the Huntington plant has been there more than a couple years.  My info on that plant came through friend Randy Baldwin from San Marcos Growers, who spoke to John Trager about the plant and said the original piece came from Gary Hammer.  Randy said he saw quite a bit of it in Phoenix when he was there, and that Mountain States Nursery was growing the plant when he visited last month."

RJB proposes that this be entered as a new variety and be labelled "var. prostrata".

Portulacaria afra prostrate form
Portulacaria afra prostrate form, photo courtesy of Allen Repashy


A corkbark form has been brought to RJB's attention by David Bogan of Lynnville, IN in a personal e-mail 03 Oct 2009.  "I recently obtained a seemingly very old (cutting started in the 60's) Portulacaria which exhibits very unusual bark characteristics.  The plant was obtained from a tropical grower who used it as a stock plant for cutting for many (20?) years.  The grower claims it was originally obtained as a cutting from a plant grown in Florida.  According to the original owner, he has always called it a 'cork' bark Portulacaria and it exhibited this characteristic from early on."

RJB proposes that this be entered as a new variety and be labelled "var. corticosa".

Portulacaria afra corkbark form
Portulacaria afra corkbark form, photo courtesy of David Bogan


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