Sedum, with 600 species, is the largest genus of the Family and the least well-defined, most of the other Sedoideae being "splits" or at one time or another included within it. It covers the North Temperate regions, with outliers extending south to Peru, Central Africa and Madagascar. and occupies an equally wide range of habitats including a few species in marshes (S. villosum) and some epiphytes (S. epidendrum). Some of the hardy species are herbaceous perennials, with leafy shoots that die down to an underground rootstock in winter. Sedum sieboldii from Japan does this, and its fine hybrid with S. telephium, 'Autumn Joy', is a well-known border plant for hot. dry places. The roseroot, S. rosea ( 10.1 ), is dioecious and sometimes classified in a separate genus Rhodiola. The creeping and prostrate perennials are legion and widely grown, but a few, such as S. album and S. reflexum (3.1), are difficult to stop from taking over the whole rock garden. A special word of praise should go to the biennials, S. pilosum and sempervivoides ( 10.13), well worth the trouble of raising from seed for their neat compact rosettes, which open out during the second year into broad
heads of deep pink and crimson flowers respectively.
More to the tastes of the average cactophile are the tender species of Mexico and North America, which are also the most succulent of the genus. Sedum flowers are small and star-like and arranged in mostly large and showy corymbs. They come in all shades including pale blue in S. coeruleum.
Rosularia, with Sempervivum-\iV.e rosettes but axillary inflorescences, extends from Asia Minor to the Himalayas, and Meterostachys and Orostachys from Korea to Japan. Although nominally hardy, these are best covered against excessive moisture in winter or removed to the unheated alpine house.
Tacitus (10.20) is the latest discovery, from Mexico, just making its way into collections. The large, vivid red flower has a corolla tube with the mouth almost closed by an overhang at the top.
The humble houseleek. Sempervivum tectorum (10.14). has had a place in history from very early times, having been credited with numerous virtues
AbovedO. 14): Sempervivum tectorum. the common houseleek ot Europe was long planted on cottage roofs as a supposed protection from lightning
Top lettl 10.16): Jovibarba hirtus ssp allionii
I western Alps is hardy and a e rock garden bearing the Howers dies.
deriving from itsabundant. cool juice and long survival of desiccation. Its country names reflect some of the supposed uses: healing blade, thunder plant, sengreen [ = evergreen] and welcome-home-husband-drunk-though-you-be. Planted on cottage roofs it is held to protect against lightning. The leaves were used, much as were those of Aloe, as poultices and cures for warts and corns, and from Columella in the first century BC we learn that soaking seeds in the expressed juice will deter pests when they are sown. A more picturesque use is in helping a country maid to select her future husband. If she picks a houseleek flower for each of her lovers, that which opens best and lasts the longest will be the one for her.
Of the 50 or more rather ill-defined species of Sempervivum, those with bell-shaped flowers with parts in sixes or sevens have by some been split off as the separate genus Jovibarba (Diopogon) (10.16). All are more or less hardy and native to Europe and Western Asia. Their tender relatives are to be found on the Canary Islands, the "tree houseleeks" belonging to the genus Aenium (5.8), which has over 30 species and numerous interspecific hybrids. Aeonium arboreum has been in cultivation since 1727 and has produced attractive mutants with leaves variegated ('Variegatum')and very deep purple ('Zwartkop' 10.15). The flower axis in Aeonium, as in Sempervivum, is terminal (10.17) and the rosette that bears it dies. For species that do not normally offset, such as A. labuliforme, this means starting again from seed, although leaf cuttings can be rooted if taken in time. Another solitary species is the giant A. nobile, justly named for its fine large rosette up to 50cm (20in) across of thick, green, slightly viscid leaves and broad corymb of many small purplish red blooms (the other species have yellow flowers). Although no aeoniums will survive a Northern Temperate winter unprotected, they are excellent plants for summer bedding in the
Monanlhes, with 18 species and nine hybrids, includes small Sedum-like plants with usually rough, somewhat crystalline leaves and a ring of conspicuous nectar glands in each flower (4.3).
Having more frost-hardy species than all the other Families of succulents put together, the Crassulaceae are as much the
Top lettl 10.16): Jovibarba hirtus ssp allionii
I western Alps is hardy and a e rock garden bearing the Howers dies.
concern of alpine and rock garden addicts as of succulent collectors. The genera Sedum and Sempenrivum. in particular, can occupy niches unsuitable to most other plants and beautify the bare corners and rough patches: chinks in rocks, walls and paths that are too dry for other plants to survive. The popularity of the latter genus led to the formation of a Semper-vivum Society in 1970. responsible for testing and certifying newly introduced cultivars.
Turning now to collections under glass, one devoted wholly to Crassulaceae can be of no little appeal and interest. The rosettes, in many pastel shades from white and powdery through shades of green, tan. yellow and pink to almost black, give the appearance of large flowers and are much longer lasting. It must be confessed, however, that to maintain such a collection in perfect trim takes more work than the equivalent collection of cacti. Once potted, a cactus can look after itself for a year, provided it is given water, without coming to harm as a rule. Many Crassulaceae quickly outgrow their space if watered, and drop their leaves if kept too dry. One must first position them carefully so that choice miniatures do not get crowded out of view by rampant growers that throw out aerial roots and trespass across other pots. In the wild many rosette plants are protected during the dry season by their old dead leaves. Sempervivoideae. in particular, can survive the most extreme droughts: even if the roots are killed off, the last part to die is the growing apex, protected as it is by a sheath of outer leaves like a bulb. In Greenovia the rosettes annually close up tight during the rest period and open out again when amply watered. In the milder conditions of cultivation, however, it is usual to remove the dead leaves, which look untidy and harbour pests. A pair of blunt-ended forceps is useful here: grasp each leaf near the base and give an outward rolling motion to twist it down the axis if it shows any resistance to part company.
Shrubby Crassulaceae quickly become leggy in pots, and benefit from repropaga-tion. The tips can be rooted as cuttings and the base kept under the staging for further propagation or planted outdoors to take its chance. Some tall-growing species are shy to branch, and it is best to pinch back the tips repeatedly when they are young to encourage formation of a neat shrublet. Clustering types such as Crassula schmidtii are apt to die out in the centre with age. and likewise benefit from repropagation.
Pest control can be a slight problem if one believes the manufacturers who warn that sprays containing malathion may be harmful to Crassulaceae. I have not found this to be so myself, but be warned! Contact insecticides such as Volck will wash off the delicate powdery bloom that is the chief attraction of many species, and it takes a long time to regenerate. However, watering the roots with systemic insecticide seems to do no harm and is the most efficient control I know.
Right (10.18): Graptopetalum tiliferum shows the characteristic mottled petals which make the Ilowers ot this small genus extra appealing ll comes from Chihuahua in Mexico
Lower right (10.19) Sempervivum giuseppii from Spain torms dense cushions ot small lurry rosettes, and is Quite hardy to trost No rock garden is complete without its full Quota of houseleeks.
Below(10.20): An exciting novelty from Mexico. Tacitus bellus was discovered as recently as 1972 Happy in a 6cm (ZViin) pot. it has a big flower of2.5-3.5cm(l-l y,in). ll offsets sparingly, but propagation is possible from single leaves
The Ice-plant Family
The Ice-plant Family
The Mesembryanthemaceae, as reference to the chart on pages 16-17 will show, introduce us to the Order Caryo-phyllales. which includes a concentration of Families of succulents, large and small. Although there would seem at first sight to be little in common between a cactus and an ice-plant, or a Didierea and an Anacampseros. they are linked by em-bryological. anatomical and biochemical as well as morphological characters to form one of the most natural of plant Orders. Reference has already been made (page 31) to the common possession of betacyanin in place of anthocyanin (2.5); the different type of red pigment in the flowers perhaps contributes to the distinctive look of the blooms throughout the Order.
The Mesembryanthemaceae have had a checkered career at the hands of classifiers. In Linnaeus's day, everything we now include here was placed under a single genus Mesembryanthemum ("midday flower"), which aptly describes the majority. Mesembryanthemum was later put in the Family Aizoaceae. along with a number of only very slightly fleshy pan-tropical weedy annuals. As the number of species introduced from South Africa increased, so the genus became more and
Below (I1.I]: Conophytum bilobum showing two leal lobes fused ai the base into a spherical body, from which the tokver emerges in the centre A new leaf pair is produced each year more unwieldy, and efforts were made at the start of the nineteenth century by Haworth and Salm-Dyck to divide it up. However, no satisfactory subdivision was possible until N. E. Brown at Kew revealed the secrets of the fruit structure in 1921, and began a systematic breakdown into separate genera. Thus to identify any member of the Family to genus, one must have the fruit to examine, although fortunately many of the popular genera can be approximately separated by eye on habit: Faucaria, Clottiphyllum, Drosanthemum. Lithops, etc.
Conservative botanists still include the Mesembryanthemum complex within the Aizoaceae, lowering the hierarchic rank to that of subfamily and the other divisions accordingly. As a supporter of conservative taxonomy, I agree with this. But the narrower concept is adopted here because it makes presentation simpler by splitting off the succulents of interest to collectors and omitting their weedy relatives. We still have a sizeable Family, which rivals the Cactaceae at an estimated number of species of around 2,000, although such figures may well be reduced after more field study. Already 22 proposed species of Aridaria have been reduced to one by examining the pattern of variation of each.
Although the splitting up of Linnaeus's
Right (11.2): Lampranthus roseus. valued tor bedding displays in trost-lree areas where there is unobstructed sunlight Lampranthus towers come in all colours except blue
one genus Mesembiyanlhemum into over 100 may seem excessive, the genera are on the whole better defined than those in other large Families of succulents, and the almost total absence of intergeneric hybrids, in the wild or made by man. suggests strong genetical isolation between the genera.
As understood here, the Mesembryanthe-maceae are annual or perennial herbs or small shrubs with simple leaves (lobed in one species) and no stipules. Beyond that, there is enormous variation in general habit, exploiting the gamut 'of xeromorphic features associated with surface reduction and water retention. Long leafy stems become telescoped into compact shoots with few leaves: flat expanded leaves into hemispheres or finger- or half-egg-shaped bodies; or two of a pair fuse to form a conical body (Dinteranthus, Lithops) or a close approximation to a sphere (Conophytum). Heterophylly (the production of two or more types of leaves on one shoot in succession) occurs in Vanzijlia. Mitro-pliyllum. Cheiridopsis and others; and leaf windows are found in Fenestraria. Frithia. Conophytum subgenus Ophthal-
mophyllum and some Lithops, associated with a semi-subterranean habit so that only the window is exposed to the light. Mimicry, discussed more fuHy in Chapter 5, is found in all species of Lithops. and to a lesser degree in several other genera. A caudiciform habit, with an amorphous underground tuber and deciduous aerial shoots, is developed in several species of Sphalmanthus (Phyllobolus). Crystalline papillae cover the leaves of Mesembryan-themum and Drosanthemum ("ice-plants") and some others, and Psammophora has sticky leaves that become clothed in a protective sheath of the dust and sand of the habitat.
The flowers are usually showy and many-petalled, which gives them a superficial resemblance to daisies and other members of the Compositae. They tend to have set hours of opening and closing; a few open at dusk, and these are sweetly scented. Few expand in the sun's absence.
The typical fruit is a dehiscent capsule: that is, a seed pod that opens mechanically to allow escape of the seeds. Both structurally and biologically the functioning is very complex, and it is discussed more fully at the end of Chapter 4. on agency causing opening and. to some extent, washing out of the seeds. Variations in fruit structure are the basis of the division of the Family into subfamilies. Tribes and genera, of which the briefest summary is given in the chart on pages 134-5.
The seeds of Mesembryanthemaceae can be 2mm (1/12th in) or more across or fine and dust-like (Dinteranthus). In tests on 253 samples in 19511 found that germination took anything from three days to a number of weeks, but annuals germinated more slowly and erratically than perennials, some coming up better the second year after sowing. This is understandable because an annual is more vulnerable to adversities of climate than a perennial: a reserve of seed allows
Right [11.3): Cheiridopsis candidissima. Abundant in the Van Rhynsdorp district ot South Africa, a collector's piece elsewhere this is fascinating even without the flowers
Below right(11.4): Pleiospilos bolusii. The dark spotted leaves resemble the granite forming the background to this species in nalure The large bloom has a fragrance of coconut
Below (11 5): Dinteranthus wilmotianus comes near to Lithops in appearance but not in ease of cultivation. Since it never branches, propagation is from seed only
THE ICE- PLANT FAMILY (MESEMBRYANTHEMACEAE)-A breakdown to genus level
Placentation parietal to bas^J
Fruit a dehiscent capsule
Fruit a hygroscopic capsule (opening Subfamily 1
Fruit a schizocarp (splitting up into separate sections)
Fruit opening when wet
Fruit without seed pockets, usually closing again when dry
Petals soft Tribe 1
Petals stiff Tribe 2
Annual Subfamily 2 HYMENO-GYNOIDEAE
Perennial Subfamily 3 CARYOTO-PHOROIDEAE
Subfamily 2 HYMENO-GYNOIDEAE
it to perpetuate after the current season's seedlings have been destroyed.
Seedlings develop in different ways: in some the cotyledons (seed leaves) elongate and are like adult foliage (Conicosia 6.19): in others they remain more compressed and succulent, so that in Herreanthus the juvenile plant looks like a Conophytum for two to four years before the expanded adult leaves grow out.
The Mesembryanthemaceae are centred in South Africa, with isolated, mostly annual species to be found in St Helena. Madagascar, North Africa and Arabia. Carpobrolus and Disphyma are perhaps native in Australia and New Zealand: the occurrence of Mesembryanlhemum in the New World seems to be the result of an introduction at an early date by man.
All but one of the subdivisions within the Family can be dealt with briefly: few of the plants concerned are of interest outside botanical circles. Taking them in the order shown in the table on pages 134-5, Mesembryanthemum in its present, narrow sense includes 40-50 species of annual or biennial, very soft, sappy, brittle herbs with mostly flat expanded leaves and insignificant pallid flowers (11.6). 1 have seen one species growing near Springbok with leaves 40-50cm (16-20in) long —the largest in the Family — and sparkling like diamonds in the sun from the papillae that cover the whole surface of the plant. So soft were the leaves that it was impossible to pick one without reducing it to a pile of mush. M. crystallinum is the original ice-plant, now widespread and naturalized in the Mediterranean area, the Canary Isles and California. Each papilla is an enlarged surface cell of the epidermis that acts like a flask for water storage. Sceletium is a flat-leaved perennial shrublet in which the old leaves persist as skeletons at the base of the plant.
Dactylopsis, which would be in every collection if it were more adaptable to cultivation. It has very long, thick anchoring roots and fleshy finger-like growths made up of alternate united leaves from which the flower extrudes like a small white shaving brush. This is strictly for the connoisseur.
Hymenogyne (Subfamily 2) and Caryolophora (Subfamily 3) are flat-leaved weeds notable only for their unique fruits, which split up into large, winged part-fruits, each with a seed that is distributed by the wind. The same applies to Tribes 4-6, whose distinctive features are summarized in the table. Conicosia has a place in collections as a robust grower with thick roots, a rosette of long, three-edged. spirally arranged green leaves and profuse yellow blooms. It does poorly in a pot but thrives with a free root run, although, being self-fertile, it is apt to seed all over the place. It has massive fleshy roots and is almost hardy. Its extraordinary fruits with three different means of seed dispersal are dealt with on page 59. Saphesia is all but extinct (pages 96 and 135).
Finally, the Carpobroteae (Tribe 7) are set apart from all the others by the fleshy, indehiscent fruit, which ripens like a fig. whence the common names fig marigold and Hottentot's fig. Carpobrotus (3.11, 12) includes vigorous, prostrate growers that cover many square metres with their rooting stems; some, which are nearly hardy and flourish on sea coasts, have been found useful for consolidating dunes. Carpobrotus (11.8) is one of the few genera of the Family to occur outside South Africa, although the extent to which it has been artificially introduced is uncertain. According to S. T. Blake, four species are recorded from Australia, one from Norfolk Island and one from Chile; the remaining twenty or so are South African. Among its species are the largest of all blooms in the Mesembry-anthemaceae. Jacobsen records that the fruits of C. muirii are dried and sold locally in South Africa, and those of C. deliciosus and C. dulcis are eaten raw.
Below [ 11.8): Most vigorous ollhe prostrate growing Mesembryanthemaceae. Carpobrotus also has the largest Ilowers Those in C. deliciosus, seen here are 7 to 8cm (2^-3% in) across
Ruschieae—the annuals and shrublets
Three quarters of all the genera come within the one Tribe Ruschieae. and almost all are plants with collector appeal. They share the common character of a fruit that opens by hygroscopic valves when wetted, releases the seeds, and closes again when dry. Schwantes divided this Tribe into 22 subtribes, partly on habit and partly on minute characters of the fruits. The best botanical treatment of the Family is The Genera of Mesembry-anthemaceae by H. Herre, 1971. Here it is more convenient to adopt the gardener's breakdown into annual bedders, shrubby mesems, stemless mesems and mimicry plants, allowing that there is overlap.
The group for annuals is dominated by those splendid embellishers of the flower border, the 'Livingstone Daisies', commonly marketed as seed of "Mesembry-anthemum criniflorum". but correctly assigned to hybrids descended from Doro-theanthus bellidiformis crossed with D. gramineus and perhaps other species. Whatever the name, they are most lovely carpeters (11.10) and ideally suited for hot dry sites on a poor soil, where Portulaca grandiflora is their only rival.
In the second group we find the large genera Lampranthus (11.2), Ruschia, Delosperma (11.12), Cephalophyllum (11.7) and Drosanthemum with several hundred species between them, as well as other lesser stars. These are seen at their best bedded in the open in full sunshine — the more sun, the more profuse will be the floral display, and under such ideal conditions as in California or southern Europe nothing can surpass the sheets of dazzling colours in early summer. Lampranthus, the favourite genus, has a flower colour range covering most of the spectrum except blue. It is best to treat these as annuals, taking cuttings in the autumn and rooting them in trays of sand and peat under the glasshouse staging ready for planting out the following spring. Attractive smaller genera are Oscularia and Malephora with grey or pruinose leaves, Eberlanzia with thorns and Trichodiadema with a cluster of bristles at the tip of each leaf giving a quaint reminder of the cactus areole. Ruschia uncinata (11.9) is the hardiest of all, in my experience, and has survived outdoors unprotected in London and Reading for many years now.
Very different from the foregoing are the Mitrophyllums (11.11), considered by Jacobsen in 1960as "among the rarest and most interesting of the Family". The interest remains, but, thanks to supplies of seed from South Africa, they are not as rare as they were. This genus introduces us to heterophylly: the leaf pair produced during the growing season is much more open and expanded than the conical, united pair that follows and remains during the rest period. Comparing a dormant plant with one in full growth, one would never think them the same species. The 29 species, which include some originally described as Cono-phyllum, form small, sparingly branched shrublets rarely more than 10-50cm (4-20in) high. Cuttings do not root readily and flowers are hardly ever seen in Europe. As suggested on page 74, this may be a day-length phenomenon that a little experimenting with shades and extra lights might overcome. The growing season is late summer and autumn. Monilaria is a related genus in which the nodes (stem joints) are swollen and look like a string of large beads.
Ruschieae—the stemless types
The plants included here have the leaf pairs so tightly packed together that there are no visible intemodes between. Faucaria is a good plant for beginners, being comparatively easy to grow if it has sharp drainage and is not overwatered. It has a few pairs of opposite decussate leaves with the upper margins usually more or less toothed or bristly. In F. tuberculosa (11.15) these cartilaginous teeth extend also to the leaf surface. Carruanthus has similar toothed foliage. The fancied resemblance of the top pair of leaves to the gaping jaws of an animal led Bradley to christen the last-mentioned 'Dog's Chaps', and the Latin epithets of Faucariafelina (ofcats), F. lupina (wolves) and F. tigrina (tigers) perpetuate similar analogies. Both genera should be watered in summer and rested dry in winter. They flower freely, and the bloom is large, yellow, and sits tightly in the centre of the rosette. In full sunshine, the leaves take on an attractive purplish colour. F. Candida has white petals. There are reputedly 33 species of Faucaria.
Somewhat similar are the Stomatiums (11.14) (40 species), which are usually smaller in all parts, but the flower colour range extends to pink (S. alboroseum). Some open their blooms at dusk and are fragrant. S. agninum 1 have found to survive outdoors in England in mild
Glottiphyllum is one of the most immediately recognizable genera (11.13), the leaves being extremely soft and juicy, typically bright green and arranged in pairs in two series obliquely on short branches that hug the soil. This is true of G. linguiforme, Bradley's'Smaller Dwarf Tongue-leav'd Fig Marygold', the type species and longest known. Many of the 57 species resemble G. linguiforme and are a little rampant in collections, but there are some fine compact species such as G. herrei with glaucous pinkish leaves. G. pygmaeum with very squat rounded leaves and G. semicylindricum (biden-tatum) with lax shoots bearing small, pustulate leaves each with two prominences set obliquely, one on either margin. Glottiphyllumshave splendid large yellow flowers (scented in G. fragrans) and deserve to be better known, at least in the distinctive dwarf representatives. The reason for their neglect is the surfeit of sprawling, badly grown, nondescript plants of the G. linguiforme type that give the genus a bad name. The secret is to keep the plants in small pots in full sun and to be utterly hard-hearted about watering: they thrive on starvation and quickly spoil if overfed.
Cylindrophyllum is another easily grown genus comprising C. calamiforme and five doubtfully distinct segregates. The long, cylindrical, finger-like leaves make it easy to recognize. Bradley called it the 'Onion or Quill-leaved Fig-Marigold'.
Bergeranthus is credited with 11 species, although only B. multiceps. B. scapiger and B. vesperhnus are common. Here the leaves are densely crowded in basal rosettes, semicylindrical, long-tapered. smooth and green, and the habit is clustering. They grow in summer, flower freely and keep out of trouble in my experience.
Right (11.13): Glottiphyllum praepingue is best kept in lull sun and starved ot water to avoid too lush, pallid growth
Below right (11.14): Stomatium jamesii has teeth on the leal margins and is covered in conspicuous papillae
Below (11.15): Faucaria tuberculosa, characterized by the marginal teeth, which in this particular species are supplemented fy
Machairophyllum has a similar but more compact look and forms large clumps. There are ten described species, of which the best known is Bradley's 'Dwarf Triangular White-leafd Fig-Marygold'. M. albidum. As he correctly tells us, "it loves a dry warm air and little
With Nananthus (syn. Aloinopsis) (11.16) we come to the midget species forming a natural link to the mimicry genera. Often the most voluminous part of the plant is the rootstock, which bears short branches at soil level with only one or two leaf pairs at the tip of each. Pot-grown, young plants look best; with age the centre becomes bare and unsightly. This is a cue to cut off the tips at the start of the growing season and propagate new plants from them. Nananthus schoonesii forms a carpet of tiny, closely packed, flat-topped leaves that look as if sheared off level with a knife. At the Worcester Gardens in the Cape, where my specimen came from, it is an abundant weed in
Right ft 1.16]: Nananthus transvaalensis— Nananthus means "midget /lower"- is one ot many miniatures approaching in habit and markings the mimicry Mesembryanthemaceae
Below ( 11.17]: To encourage flowering, as in /teCheiridopsis. stemless members otlhe Mesembryanthemaceae need lull sun and an annual rest period when they are kept Quite dry
Left (11.18) Didymaotus lapidilormis. an excellent example of natural camouflage amid granite rocks in habitat at Beukesfontein. S. Africa. This endangered species was growing within feet of an expanding quarry.
Ruschieae—the mimicry types
We now come to genera where mimicry, as defined on page 71, is the rule rather than the exception (5.10). The preceding genera are not particularly difficult to keep, once one has mastered the essentials of porous soil, light and observation of the resting period. Since they adapt to summer growth in the Northern Hemisphere this is no problem. Now we turn to plants that are not only among the great prizes of collectors, but they include a few that tax the patience in efforts to preserve them alive. Didymaotus is one example. Not many growers manage to keep it for more than a few years, and if they do it looks nothing like the "split rock" it is in its habitat (11.18). Jacobsen recommends full sun, little water and a resting period
Pleiospilos, no less attractive in its dwarf species P. bolusii (11.4) and P. nelii, is fortunately much easier to grow. These two species, each with one or two pairs of almost hemispherical leaves of greyish colour with darker spots, look like granite pebbles. Others of the 33 species have more elongated lea ves (11.19) and some form large clumps. The showy yellow flowers come late in the season and sometimes smell strongly of coconut.
A different type of "mimicry" is shown by Titanopsis (11.20), which grows chinks between the paving stones.
Cheiridopsis is a genus of great appeal to collectors, no species being unworthy of attention (11.3,17), even if it is hard to believe that over 100 merit recognition as separate species. All are highly succulent and dwarf species and, like Mitro-phyllum. show a degree of heterophylly, the resting plant looking very unlike a growing one. C. peculiaris shows this in a marked degree. This is a true mimicry species, found only against purplish brown rocks, which its bronzed foliage matches perfectly. When in the dormant condition the expanded leaves die back and are replaced by an erect cone that protects the growing centre from desiccation. C. candidissima. looked upon as rather a choice and costly rarity in cultivation, is extremely common in parts of South Africa; uncountable clumps, 30-50cm (12-20in) across, dominate the flat open landscape with their trim, glaucous, pointed leaves and white to pale pink blossoms—a magnificent sight.
Left (11.18) Didymaotus lapidilormis. an excellent example of natural camouflage amid granite rocks in habitat at Beukesfontein. S. Africa. This endangered species was growing within feet of an expanding quarry.
among quartz rocks and has a white crystalline appearance from large papillae covering the leaf tips. A much-quoted story tells how Professor Marloth. a leading authority on the African flora, discovered T. calcarea by accident when he rested against it under the impression that it was a rock. All five species are distinctive in leaf patterning and immediately attractive to the collector, but it is best to raise seedlings every few years because they tend to be short-lived and die without warning, so can hardly be recommended to beginners.
Neohenricia is like an even smaller version of Titanopsis but its tiny flowers open at dusk and exhale a powerful fragrance that would justify the inclusion of N. sibbettii, the only species, in a collection even if the plant were less demure and charming. Fortunately it is easy to grow and propagates readily from
Fenestraria and Frithia are taken together because both have "window leaves" (page 24). the rosette being buried in the soil with only the translucent tips
Above (11.22): Frilhia pulchra is superficially like Fenestraria. but not closely related It is a short-lived perennial, propagated only from seed, and comes from the Transvaal. S. Africa
Below(l1.23): Most species ol Gibbaeum have the leaves of the pair unequal in size This is G. dispar in a 7cm (2\in) pot The leal surface is velvety and the flower purplish pink.
of each curved, club-shaped leaf exposed to the sun. In cultivation they are grown above soil. But the two genera, both of one species each, are not closely related. Fenestraria aurantiaca, 'Baby's Toes' (11.21), is the easier to keep; it has flowers of various shades from buff to pinkish yellow, and its form rhopalo-phylla is white. Dividing a clump is the easiest means of multiplication. Frithia has vivid crimson blooms (11.22) and forms no offsets. It is short-lived and can only be raised from seed. It rests in summer and needs watering in early spring.
Gibbaeum introduces us to another popular genus including 21 species of compact but diverse form whose linking character is the lopsided leaf pair. Occasionally the two leaves are only slightly unequal in size (G. esterhuyseniae with expanded leaves; G. cryptopodium with leaves fused into an egg-shaped body). In G. pubescens the lea ves are very unequal, one being represented only as a small lobe at the side of the other. Nel. whose unfinished monograph of the genus was published posthumously in 1953. records that all species of Gibbaeum occur in an area of the Little Karroo 135km (85mi) by 40km (25mi) with two outliers to the northwest, G. gibbosum and G. heathii Within the main area some species are widespread, others local. G. schwantesii is limited toa patch about 90m* (100yd*), so is of concern to the conservationist. Up to six species grow sympatrically (that is, side by side in the same area) and there is a fascinating field for study here on the nature of the barriers that prevent hybridization in the wild. In cultivation, flowering is at the start of the growing season; this differs from species to species, and may contribute to keeping the species apart in nature. Authorities differ with their watering recommendations for Gibbaeum: it seems safest to play it by eye, watching each plant for signs of awakening, and easing off watering after it has flowered. G. album, dispar (11.23) and velutinum seem to prefer to grow in
Close to Gibbaeum, and one of the most specialized of all succulents, is the extraordinary monotypic genus Muiria. Its anatomical peculiarities are mentioned on page 12. At the classic habitat I visited in the Little Karroo in 1971, Muiria hortenseae was confined to one of many quartz patches a few metres across. Outside the patch, none was to be seen. Inside, they were so thick on the ground that one could not step without treading on them. Each plant looks like a circle of ripe, downy greengages: the two leaves of a pair are so completely fused that only a tiny slit on one side shows where they join, and through this the brush-like flower emerges. Unfortunately this wonder of the vegetable kingdom resists ir the advances of cultivators, although large numbers have been imported in
Argyroderma, the 'Silverskin' (11.24), has been the subject of a recent monograph by Heidrun Hartmann, who recognizes ten variable species. The growths are solitary or form a clump, each made up of two opposite leaves shaped like a halved egg or a short finger and characteristically quite smooth and silvery grey. The flower colours are white, yellow or purple, but can vary within one species. The growing period is in middle to late summer when minimal watering should be given, just to prevent shrivelling. Argyroderma is prone to develop brown disfigurements or split if overwatered. Full sun is essential.
Of rather similar form, but closer to Lithops in body markings, is Dinter-anthus( 11.5), with six species, all collec tors' pieces and reputedly ephemeral in cultivation. D. vanzijlii has been mistaken for a Lithops, from which it can be distinguished by the ten-celled capsule and the smaller seeds, perhaps the most minute in the Family.
Conophytum (11.25, 26), with 315 species described by Jacobsen, only awaits a modern monograph to launch it into the popularity it deserves. An evolutionary climax group within the Mesem-bryanthemaceae, it shows maximum surface reduction in relation to bulk, and a most efficient and economical life form, in which a single body composed of two united leaves withers to protect the next season's bud and transfers its stored food to nourish it. During half the year a Conophytum looks dead: but do not despair! Life goes on beneath the brown leathery sheaths. Keep it dry and at most just moisten the topsoil until the plant itself gives the cue to begin watering by starting to split open the sheaths. Some Conophytums have almost spherical bodies; others, the bilobes. have the two leaves free at the tip (11.1). Forboth sorts the growing season is late summer, but the bilobes make an earlier start, so watering for them should begin around June; for the others, a month later, ! stopping at the end of the year. Conophytums in nature are lithophytes: plants growing in rock chinks and cliffs with a minimum of soil and water. I have seen bare rock faces clothed in mats of Conophytum that could be stripped off like lichen; indeed, one marvels how any I plant can survive in such spartan conditions. Yet they adapt well to pot culture if the correct watering ritual is observed, and a collection of specimen plants is I indeed a sight (11.29). especially when I covered in yellow, white, orange and red
Above lettl'1 25): Hugging the. Conophytum eclypum in habitat in Lttue Namaqualand Each 4-6 mm (% in) head of two leaves is renewed each growing;
Right (11.26): Conophytum saxeta Namibia Each tiny growth is only 2-Chr'kin) across The plants grow oi lichens which they superficially resemble blooms. The white flowers are mostly nocturnal and fragrant. It takes many years to build up a large clump from a single head, but they are remarkably long-lived and tolerant of neglect, seeming none the worse for standing on a top shelf for years without repotting. Ophthalmo-phyllum, sometimes treatedasa separate
genus, is a subgenus of Conophytum with windowed leaves.
Finally we come to Lithops (5.10). at once the most popular and most distinctive of all genera of Mesembryanthema-ceae: the renowned "pebble plants" or "living stones". The body here is reduced to a single pair of opposite leaves united into a cone (2.11). with a fissure across the centre through which the flower emerges and then the next leaf pair, at right angles to the old. Some remain solitary: others branch to produce small clumps by developing two leaf pairs from a single head. As in Conophytum, the old leaf pair nourishes the new and the delicate growing apex is safely hidden below soil near the base of the cone. Unlike that of Conophytum. however, its growing season readily adapts to the
Northern Hemisphere cycle, so if plants are kept quite dry in winter, and watered only after the skin has started to split to reveal the new body, all should be well. Overwatering produces a grotesque, untypical appearance (6.2).
Lithops grows buried in the soil, only the flattened leaf tips being exposed. These are never plain green but usually elaborately mottled and spotted, and harmonize with the colours of the surrounding soil. This "mimicry" is further discussed on page 71, The colours and patterningare the chief characters whereby the 37 species are identified, together with the flower colour, which is either yellow or white. The recent conservative classification by Desmond Cole (1973) is the best so far. Lithops is a perfect subject for a specialist collector with ample sunshine but little space. As in Conophytum, all the species can be accommodated in small pots, and maintenance is minimal. They are among the easiest Mesembryanthemaceae to raise from seed, and singularly free from pests and diseases. No collection should be without at least a few species of Lithops: they are among the marvels of the vegetable kingdom and never fail to excite great interest and comment from visitors. Cultivation
Mesembryanthemaceae are creatures of the sun, and resent shading more than most succulents. The stems elongate, the lovely glaucous bloom and coloured markings become a pallid green, and flowering is suppressed. Therefore in any mixed collection of succulents they should head the queue for sites in the sun, preferably close to the glass. The shrubby kinds do well outdoors in summer, and because winter temperatures do not need to be high and aeration is important, a frostproof frame can be put to good use for the less delicate sorts. Good air circulation is important at all times, even in winter on milder, brighter days. Where smog and other adversities afflict the local flora, plants that change their skins once a year are at an advantage. One of the most celebrated collections of dwarf Mesembryanthemaceae long throve in Hounslow in the suburbs of London, which is not renowned for either pure air or high light intensity.
The importance of a restraining hand on the watering can has already been stressed: watch the plants and they will tell you when growth is commencing or when, after flowering, a rest is needed. Those that insist upon growing in winter — Conophytum. Dactylopsis, Frithia, some Gibbaeums. etc — must be watered cautiously and supplied with extra warmth and all the light possible. Nothing rots a succulent quicker than standing in cold damp soil. Hence it may be necessary to shift the pots around in autumn to obtain the favoured places for winter growers.
Propagation by both seed (6.19) and vegetative means is possible for most species. A few, such as Mitrophyllum. root with difficulty, and for single-headed plants such as Frithia. and some Lithops and Argyrodermas. seed is the only way. Single leaves, even if you can root them, do not regenerate plants. When taking cuttings of a dwarf Lithops or Conophytum. be sure to cut as low as possible, at the narrowest point. If you miss the growing apex near the base of the cone, the attempt will be in vain.
Below (I 1.29]: Part ota collection of Conophytums. small plants ideal lor the specialist with little space Large clumps like this take many years to develop
12: PORTUL ACACEAE
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