an ongoing monograph which contains some of the areas of
both knowledge and ignorance pertaining to this plant"
© 1999-2024 by Robert J. Baran
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APPEARANCE Please see this recent gorgeous video about Portulacaria afra in the Western Cape of South Africa to better appreciate this section. 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. Container specimens of P. afra is sometimes still sold as Crassula portulacaria, the plant's 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 (8.2 to 14.75+ feet) tall. The diameter of the trunk can be 20 cm (7.9") or more. (Jacobson 2008 notes that "Portulacaria is a stout shrub or even small tree 15 (rarely 20) feet [14.6 to 16.1 meters] tall with a trunk that can be 3 feet [~91.5 cm] thick.") The life expectancy of the plant, while demonstrated to be over 50 years, is unknown. (McCarthy gives an otherwise unsourced figure as "up to 200 years.") "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 (about 12") in diameter. This P. afra was worked on at the owner's request c.mid-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 [sic] 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.) "If left undisturbed Portulacaria grows into a much branched tree with a maximum height of 15 t. and a trunk up to 9 ins. in diameter, the crown having a spread of about 10 ft. Such trees only exist where they are well protected by other vegetation as there is very little woody tissue in their stems and they are easily broken. The plants coppice freely and the usual form of propagation is from fallen stems, which retain their vitality for some time if conditions are not favorable for root production. Dense clusters of individuals 4 to 6 ft. tall are of frequent occurrence and because of this variable habit of growth it is very difficult to estimate the number of individuals per unit area." (Archibald, pg. 146) 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 height as 4.57 m (14.86 feet). "Hundreds of years ago, prior to the advent of large-scale livestock farming, the north-facing slopes of Samara's mountains on the southern flank of the Sneeuberg Mountains in the Eastern Cape were covered in Spekboom thickets so dense that it was said a grown human could walk along the top as if walking on a carpet. Many decades of livestock grazing have reduced Spekboom's footprint to a fraction of its former extent." (per the 2019 Samara article and material on its website). Spekboom "is the dominant tree of the thicket ecosystem that used to cover up to 5 million hectares (about 50,000 sq.km. or 19,305 sq miles) across the dry areas of the Eastern Cape, until about 200 years ago, when massive overgrazing by goats and sheep started (2019 UN). P. afra currently occupies approximately 1.7 million hectares (about 17,000 sq.km. or 6,564 sq miles) in the eastern and southeastern Cape where it can form a closed canopy scrubland (Mills et al in Guralnick, 2017).
"The Noorsveld...
is essentially a farming area of about 855 square miles. It is the centre of the Angora goat industry and
includes portions of the magisterial districts of Jansenville and Somerset East. (van der Walt, pg. 215) 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.) While P. afra is mostly known as an informal upright or weeping tree in the wild, location could also
cause it to be a cascade. The following two 2019 photos by South African Johan Prinsloo show
"Cascade in habitat. Graaff-Reinet, East Cape South
Africa. Very hot and dry climate. Grow in very sand Rocky soil. ...Could not get in there
to see [trunk width]. Too steep." (Reprinted by permission.)
The following two 2020 photos by South African Niel Nel show "Ports in their natural habitat." Oudtshoorn, Southern Cape region. (Reprinted by permission.)
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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 in Phoenix, AZ to air temperatures not less than -6 °C (22 °F). This matches what has been observed in South Africa (Oakes in Guralnick, 2017). 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 desiccated. 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. The ability to withstand frost in the wild is aided by the density of the P. afra stands (Palmer and Pittman in Guralnick, 2017). Per Duker et al, "P. afra (spekboom) plants were severely damaged when directly exposed to frosts that occurred on valley floors, whereas those on valley slope remained, by-and-large, unaffected. Spekboom plants that were planted underneath the protective canopy of a thicket-clump on the valley floor were also not noticeably damaged despite sub-zero temperatures below the canopy, whereas those in the open had signs of frost damage... Spekboom plants do not appear to be morphologically well adapted to freezing, as they are tall growing, and are not covered in protective trichomes, and this is likely to play an important role in its severe intolerance to frost. If directly exposed to frost, plants can be severely damaged by the formation of ice within their tissues. This may lead to not only membrane lesions and cellular component leakage, but also severe dehydration stress as water becomes metabolically unavailable as it freezes. This leads to the destruction of photosynthetically-active membranes inside chloroplasts, and photoinhibition upon illumination... On the frost-prone valley floor of the study site, we observed that spekboom individuals were restricted to beneath the canopies of thicket clumps that are comprised of a specific suite of more frost-tolerant species associated with spekboom-thicket of the valley slope." 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. See also this article from The Annals of Botany Vol. 26, Pt. 2, 1912 on "The Comparative Anatomy of the Genera Ceraria and Portulacaria" by Margaret Rutherford Mitchell. |
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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.) There are credible reports of plants with white flowers, and also larger flowers growing in small tight clusters. In South Africa P. afra bears these star-shaped flowers in winter to late spring in the warmer more humid parts. The plants will flower when rain occurs after severe drought anytime in spring through summer. It 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 more 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. Borne at the end of the stem in clusters, they are rich in nectar and wildly attractive to bees and other insects. Flowering elephant bush are popular plants with songbirds who gather to feed on the insects surrounding the blooms. 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 The 12th edition of the Catalogue of Plants, which are Sold by Conrad Loddiges and Sons, Nurserymen, at Hackney, Near London (1820) lists the old name "Crassula portulacaria" on pg. 16 as a Greenhouse Plant. The 1880 edition of Belgian horticulturist Louis van Houtte's Plantes de serre (Greenhouse Plants) included Portulacaria afra on pg. 126, in the section Serre Froide (Cold Grenhouse). There are at least five green forms (first available for sale by a California nursery catalog since at least 1929 and a New Jersey nursery catalog since at least 1931), including "macrophylla" which 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, "Skyscraper" which is narrow and upright (since before 1980 in South Africa), and minima "Lilliput", a dwarf green variety with a slight point on the leaf apex, leaves no more than 1.3 cm long and 1.0 cm wide, and reddish stems, patented in 2013. Then there are these six named variegates: "Aurea" is a form (new by the early-1960s) having a reddish stem with small bright yellow leaves, flushed with pink underneath or pink edged, and which eventually turn with age to light green featuring a yellow center.
"Gold" has its new leaves emerging
completely golden ochre before they fade to bright lime. "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."
"Variegata"
(from a California nursery catalog since at least 1942,
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.
Said to be able to take a minimum temperature of
2 °C (35 °F). (Per https://mp.weixin.qq.com/s/-nVWkfKwlx6aiIAtr46TmA,
aka "Dance of Yale") "Medio-picta" (aka Midstripe Rainbow Bush) has green, waxy leaves with whitish markings spreading from the centre and bright red or pink stems. It is said to be the most tempermental of the varieties, needing a hot/warm location, quickly drying substrate, and over 12 hours of bright light each day. "Manny" is a product of a naturally occurring mutation found in a Vista, CA commercial nursery in April 2014. After at least 15 generations of reproducing true to type, a patent for it was granted in 2020. This variety exhibits thicker and wider orbicular to broad spatulate leaves, an unusual subtle variegation, producing an overall marbled mint green colored leaf with slender pale yellow margins.
Variegated forms are slower growing and smaller than the green varieties of the species. They need to be
planted into oversize containers in order to more quickly/better develop their roots and trunks -- or, if the
climate is hospitable, planted in a garden growing bed. RJB proposes that this be entered as a new variety and be labelled "var. prostrata".
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."
Portulacaria afra corkbark form, photo courtesy of David Bogan
A unique recent variety produces both primary green and secondary pale pink leaves on the same plant. This
was brought to RJB's attention by Yip Kok Kai of Kuala Lumpur, Malaysia in a Facebook group post 17 Feb 2019.
This specimen is said to have been purchased at a nursery there in late 2018, "most probably imported from
China. Price 20 USD." At least some of the pink leaves are noted as fading to white. Per the
owner, "some said it's injected with some chemical....we will wait and see." It definitely is a unique
color scheme which we are interested in learning more about as the plant matures. (Hopefully it is not the
result of artificial biochemical stimulation which might wear off or have long-term harmful effects.)
(Per https://mp.weixin.qq.com/s/-nVWkfKwlx6aiIAtr46TmA,
aka "The Hua of Yale.")
Portulacaria afra bi-color form, photo courtesy of Yip Kok Kai in Facebook posting And then a Portulacaria afra variegated corkbark form was known by the year 2020. We are aware of other varieties existing, which will eventually be pictured and/or described here.
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