| Aloes—Big, Medium and Small
With several hundred species, the genus Aloe contains enough plants to be worthy of the many published books—some multi-volume—devoted solely to it. How then to discuss it in a short column or two? Any number of ways to break the genus down into a more manageable format suggest themselves: by botanically related sub-groups, by geographic location, by ease or difficulty in cultivation, or simply by size. Since the ultimate size a plant will grow to has to be a primary concern of anyone growing it, that can serve as a starting point for this discussion, with other elements included to give a bit more depth on the subject.
Aloe (the key genus in the family Aloaceae, carved out of the older Liliaceae) range in size from large, multi-branched trees to tiny rosettes no more than an inch or two across. Many species grow tall, others remain relatively low to the ground but produce many offsets that can dominate a landscape, and a few odd ones hang downward pendently from cliffs. Some aloes will bloom and remain permanently happy in a smallish container, others need great amounts of root room to thrive, much less flower. So, which ones are which?
Fortunately, the many species more or less sort themselves out into logical groups, and we’ll start from there. The most immediately impressive members of the genus are the largest species, those plants typically referred to as tree aloes. They’re native to the southern part of Africa, South Africa itself, Namibia, Mozambique, and surrounding regions, as well as the giant island of Madagascar and beyond. The largest number of the plants in this group form single trunks (occasionally branching from well up on the trunk) ranging from six to over twenty-five feet in height, and most of these species grow in the eastern and southern parts of South Africa.
Some, such as the spiny leaved A. marlothii, the very widespread A. ferox, or the often branching A. speciosa, are quite cold hardy (A. marlothii, in particular, can take about anything Bay Area climates can dish out). Some of the others, however, from the more tropical eastern parts of South Africa or other warm climates, have little or no resistance to hard freezes below the mid-twenties Fahrenheit, and some won’t survive any frost at all. A. alooides, with downward facing, deeply channeled leaves and an unbranched, upright flower stalk is one of the species that will survive a reasonable amount of cold (it has withstood the low mid-twenties in my yard), as will the dry-growing A. comosa (from a winter rainfall area), A. lineata, and A. rupestris, while A. littoralis and A. pluridens are a little more sensitive. Some very attractive species such as A. angelica and A. thraskii will thrive in southern California but are more doubtful subjects for the Bay Area, and the same is generally true for tall growing Madagascan aloes such as A. vaombe and A. suzannae.
A few tall species, very rare in cultivation, live in the southwest part of the Arabian Peninsula, in Yemen, including A. eminens, a multi-branched near look-alike of A. barberae, growing up to fifty feet in height, and the slightly smaller, single stemmed A. sabaea. These Madagascan and Arabian plants will do all right in large containers, but it’s best to remember that many of them wish to be at least fifteen feet tall, and unless you have a really big container and a greenhouse or conservatory with a high ceiling, the cold-sensitive ones in particular will never reach their full potential. The species that will tolerate our weather, however, offer quite a bit of variety, some with spiny leaves, some with mostly smooth leaves, some gray leaved, some blue leaved, with variously branched and unbranched inflorescences, and flowers yellow, orange, red, or oddly bicolored (as in A. speciosa).
The largest aloe of all, Aloe barberae (often called A. bainesii), which can form a multi-branched tree well over fifty feet tall, can withstand slight frost, but a hard freeze will kill it dead. If given shelter, warmth, adequate root room and a decent amount of water, however, this aloe grows remarkably quickly. Mature plants look much like any other tree, except that at the ends of the branches they produce rosettes of succulent leaves like a typical aloe. A. barberae comes from the semi-tropical east coast of South Africa, bordering the Indian Ocean. The other aloes related to it, however, grow in the north and west of the country, extending into Namibia as well. These include the rather commonly encountered A. plicatilis, with fans of soft, fleshy leaves at the ends of its branches, the somewhat less often seen A. dichotoma, with a thick, almost caudiciform trunk surmounted by many tight branches, and the tall-growing, very rare A. pillansii, perhaps the most Dr. Suess-like of all aloes and of almost any plant, close to extinct in the wild and uncommon in cultivation. A. plicatilis, from the vicinity of Cape Town, frequently encounters frost and over thirty inches of winter rain a year, and generally does very well in our area. A. dichotoma also regularly withstands hard frosts, but its habitat is so dry that our winter humidity can turn it to mush in a bad year; it is marginally hardy outdoors, while A. pillansii is at least as sensitive to excess humidity and less cold hardy as well.
Another selection of aloes, more freely branching and never growing quite as tall as the first batch, but good-sized plants nonetheless, include the extremely common, large, shrubby Aloe arborescens, very easy to grow, which will form a sort of multi-stemmed hedge or thicket, perhaps eight feet tall and several times as broad. A. ramosissima, with a multitude of branches is smaller, and looks almost like a cut-off top of an Aloe dichotoma, to which it’s closely related, and with which it shares an aversion to too much water and humidity. Another heavily branching plant from arid surroundings is the somewhat uncommon A. pearsonii, from the Richtersveld desert of northwest Namaqualand in South Africa. Plants of this species send out masses of single upright stems densely clad with very thick leaves whose flat tops face the sun. Other often multi-stemmed, rather large aloes include A. spicata, the similar A. vryheidensis, and A. castanea, all three with unbranching inflorescences thickly covered with stem hugging brown to orange flowers, almost like a giant cattail. A number of related, smaller branching, almost vining aloes include A. ciliaris, with deep orange flowers, A. striatula, with yellow flowers, and A. tenuior, with either orange or yellow flowers. This last trio of plants can withstand cold and a lot of water, and do better in semi-shade than in full sun.
Though this list of fairly to very large aloes is far from complete, it’s probably time to move on to some of those dwarf aloes suited for growing in small to medium sized pots. Though a number of these are South African (and I’ll start by discussing them), at least as many come from Madagascar and the arid lands of east Africa. Aloe aristata, probably the most common of these in cultivation, and a very satisfactory plant to grow either in a container or in the ground, used to be very common in the wild as well, but a popular belief that plants placed on a house will provide protection from lightning has led to its removal from habitat (actually the belief centers on another plant, Haworthia limifolia, but since this once common species has been collected almost to extinction, anything vaguely similar—in this case both plants have dark leaves—now will do). At any rate, A. aristata grows to about six inches in diameter and height, and sends out a branched flower stalk about two or three times as high. Some forms offset freely, others less so, and the rosettes, composed of large numbers of tight, dark, rather black-green leaves will ultimately form small mounds in a well drained garden with just a bit of shade and not too much water.
Aloe humilis forms a four inch rosette of a few upright pointing, spiny and bumpy leaves. It’s easy to grow, but the rather similar looking A. longistyla, about the same size and with leaves even spinier and a very short but proportionately huge inflorescence, can be quite difficult to cultivate.
Aloe bowiea (formerly given its own genus as Chamaealoe africana) is a small clumping plant with rosettes of soft leaves and barely discernable spines. It does well in containers and will survive surprisingly low temperatures. It’s somewhat similar to a group of generally inconspicuous plants known as “grass aloes,” which make their living concealed among the grasses of the South African veldt. Some of these plants are quite tiny and all are rarely cultivated. Closely associated with the grass aloes, A. chortolirioides forms elongated stems for its clumps of soft, elongated rosettes.
Finally, among the small southern African species, we find the “partridge breast” aloes, which make small rosettes of a few very thick, highly marked, triangular leaves. A. variegata, with a wide natural range over much of South Africa and Namibia as well, has long been a popular plant in cultivation. Its much scarcer relatives are A. dinteri, smaller and chocolate-brown when given enough light, and A. sladeniana, even smaller, like a miniature A. variegata with a slightly more open rosette. Some forms of A. variegata can reach a foot across, A. dinteri only about half that size, while a clump of A. sladeniana will have room to spare in a five or six inch pot. Though harder to find than to grow, these two small species should be given a great deal of light and a very rapid draining soil. They need protection from winter cold, humidity and rain as well.
The small aloes of Madagascar include both extremely distinct plants and some which seem to be miniaturized versions of the ubiquitous spotted aloes that range over almost every part of Africa with a fairly dry climate. The plants that I think of as having leaves with a texture like the tail of a lizard, A. albiflora and A. bellatula, are among the very distinct plants, growing into small clumps of stemless rosettes three or four inches across and maybe eight to ten inches tall. The two species seem almost identical out of flower, but the blossoms of A. albiflora are little open bells of pure white (a rare color in the genus), while those of A. bellatula are a much more standard pinkish-orange. Neither plant causes difficulty in cultivation, although A. bellatula seems a bit more delicate than its cousin, but both need reasonable warmth, subdued light for an aloe, and a just bit more water than most species during their winter rest.
With similar cultivation needs but a completely different appearance, Aloehaworthioides is a tiny plant, with rosettes rarely more than three inches in diameter. Its narrow, dark brown leaves are edged with soft, fuzzy spines, and its tiny yellow-orange flowers smell of honey. Some forms offset quite readily, and this species is fairly common in cultivation. A. parvula is a very small, still uncommon plant, with individual rosettes rarely more than three inches across, and though the plants slowly clump, a four or five inch pot will hold a mature specimen with no problem. A. parvula likes very bright light, and when properly grown its almost fuzzy leaves, equipped with tiny, harmless spines, will turn a gray-purple in color.
From a habitat of limestone hills, another odd, rare, tiny Madagascan aloe, Aloecalcairophila, grows distichously rather than in a rosette, with its two ranked leaves looking like an opened fan no more than three or four inches from tip to tip. A. descoingsii, with bright, shiny leaves marked with white spots, forms rosettes that are even smaller, rarely three inches across. Its bright orange flowers, shaped like tiny closed bells, are among the smallest flowers in the genus. It needs bright light, but otherwise is easy to grow and surprisingly cold hardy for such a tiny, almost equatorial plant. A. rauhii, somewhat similar, but with rosettes a little larger and more typical aloe flowers, will grow in lower light, but in ideal conditions of brightness its leaves will turn from green to lavender or even somewhat orange, always with an attractive pattern of white “H” shaped spots and dots.
Aloerauhii is one of the parents of many small, highly patterned aloe hybrids that are becoming increasingly popular these days. Aloe bakeri differs from these other Madagascan miniatures in that it forms an elongated more-or-less upright stem, up to eight inches tall. At the ends of its stems it produces rosettes of narrow, quite thick, shiny greenish-brown leaves, often with a few spots to provide variety. A. bakeri grows readily and sends up many stems. It will grow outdoors in sheltered parts of the Bay Area if given some sun and good drainage.
East Africa also has its share of small and near-miniature aloes. A. jucunda, from Somalia, looks like a slightly larger version of A. descoingsii, with shiny green leaves decorated with patterns of white spots and lines, although its flowers are quite different. A.dumetorum, from the dry north of Kenya, gets a bit larger, up to six inches across or so. Its leaves, pale green patterned with white, have a very distinctive, almost gray tinge. The Ethiopian Aloe jacksonii has flat-topped, gray-green, white-spotted leaves, and a growth habit much like A. bakeri, producing clusters of small, upright stems.
This column has at least scratched the surface in regard to large and small growing aloes. In the next I’ll discuss some of the medium-sized species, which include some of the most interesting and exotic as well as some of the most common, and, frankly, boring ones. I’ll also go into more detail on culture.
The Garden has a fine collection of aloes of most sizes, and we always have some on hand to sell, including, from time to time, some very choice species and hybrids.
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