| Haworthia—Part 2
The second and third subgenera of Haworthia, distinguished from the first and from each other by details of their flower structure, include many species with features in common. These include leaves marked by white tubercles, leaves opaque (rather than translucent) green in color, and often and upright, somewhat columnar growth form. Of course, a number of species in each subgenus are exceptions to these broadly described types, and these include some of the most interesting haworthias.
The subgenus Hexangulares, with flowers with a somewhat hexagonal shape at the base, includes both very common and very rare species. The most common ones, hard to kill and quick to offset, have made their way into many everyday gardens where they thrive with a mix of sun and shade. The most frequently seen is a plant that forms small, highly proliferous rosettes with upward growing leaves heavily dotted with white tubercles. Many of these plants are unidentifiable garden hybrids, with Haworthiaattenuata somewhere in their ancestry. The actual H. attenuata itself doesn’t look very different from these hybrid forms. Haworthiaattenuata var. radula, sometimes known as Haworthiaradula, has smaller, less distinctly marked tubercles, and though hardy and quick growing, is less hardy than the typical form. At first glance resembling H. attenuata, Haworthia fasciata actually is both slower growing and more attractive, with tubercles that grow in definite bands, sometimes almost like a zebra’s stripes, and only on the plant’s outer leaf surfaces. H. fasciata f. browniana is a drier growing form, with a bit of an elongated stem and heavier leaves that attain a glossy, almost frosted sheen in good light.
A second group in this subgenus consists of plants with smaller leaves, also usually heavily tubercled, that slowly grow into masses of little columns. The two main species with this habit, Haworthiacoarctata and H. reinwardtii, include a wide diversity of forms, complicating identification. H. coarctata and H. reinwardtii grow in distinctly different parts of the Eastern Cape Province of South Africa, but that is little help in distinguishing plants growing in adjacent pots. Typically H. coarctata has proportionately thicker leaves, arranged less densely on the stems, but not always. A form of H. coarctata without tubercles was once called H. greenii, though currently the presence or absence of such surface details is considered taxonomically insignificant. The most attractive members of this group are those with smaller leaves that make more striking columns. These include H. coarctata var. tenuis, and a number of forms of H. reinwardtii of varying taxonomic significance, plants such as f. kaffirdriftensis, with small, overlapping leaves and extremely distinct tubercles in longitudinal rows, f. chalumensis, a relatively quick column maker, f. zebrina, with tubercles arranged in distinct lateral bands, and var. brevicula, a miniature, rather delicate variety. Some of these plants are almost as common in cultivation as the forms of H. attenuata, standard components of succulent dish gardens, while others are extremely slow growing and rather easy to rot, ensuring their desirability for collectors.
A third group in this subgenus consists of plants that make columns of three-ranked, rather triangular shaped, solid-colored leaves. Both Haworthiaviscosa and H. nigra grow in this manner, forming, when happy, masses of upright, three-fold columns that range in color from olive-orange to almost black. Both species tend to grow slowly, though H. viscosa and its various forms (as many as fifteen now largely disregarded varieties have been described in the past) grow just a bit more quickly and become larger, with columns ultimately up to a foot tall and a couple of inches across. Haworthia nigra remains smaller, and its leaves often display a heavily sculpted surface, marked with dark lines and ridges in distinct patterns. Some of its forms, such as the plant once known as H. nigra var. schmidtiana (now just considered a variant of no taxonomic significance), can be almost unbelievably slow growing, producing no more than one or two leaves a year, and remaining content in a 2 ¼ inch pot for decades.
A fourth group of plants in subgenus Hexangulares contradicts almost all of the previously mentioned characteristics of the subgenus other than flower form. This group centers on the widely distributed Haworthiavenosa ssp. tessellata, a plant that forms compact, low-growing rosettes with flattened, translucent leaves. This plant ranges from the winter rainfall regions of southern Namibia a thousand miles east to summer rainfall areas of the Free State and Eastern Cape provinces of South Africa . Most forms have an attractive tessellated (checkerboard) pattern on the tops of their leaves, though some lack it. Leaf color varies from bright green to bronze to almost black in various forms, but almost all of the forms are easy to grow and produce offsets freely, generally at the ends of short underground stolons. Other subspecies of H. venosa are seen much less frequently, and include ssp. venosa itself, looking like a somewhat dried out, checkerboard-free version of H.tessellata, ssp. granulata, with blackish, barely translucent leaf surface, very slowly forming columns that somewhat resemble H. nigra, and the very rare ssp. wooleyi, a small, delicate non-offsetting form that looks somewhat like a miniaturized H.tessellata with more elongated, upright pointing leaves. This plant, possibly the slowest growing of all haworthias, is also now probably extinct in the wild. It was native to a tiny strip of land which ended up as a severely overgrazed, eroded gully on the wrong side of a fence. Fortunately, the species has been propagated by seed, and so still exists in cultivation if not in its habitat.
Also under imminent threat of extinction, Haworthialimifolia, typically forming flat, star-shaped rosettes of green-black leaves with lateral ridges on the surfaces like a tiny washboard, until recently was quite widespread and common. It and a couple of associated haworthias live far to the east and north of the others, extending almost to the South Africa-Mozambique border. Unfortunately, local people have decided that the plants, if pulled out of the ground and placed on their homes, will protect them from lightning strikes, and consequently H. limifolia, along with some other only vaguely similar succulents, are in the process of being eradicated in habitat. Originally much rarer in nature, H. koelmaniorum and its distinctive variety mcmurtryi look a bit like a cross between H. limifolia and one of the windowed retusa-like species. Unlike the proliferous, easy-to-grow H.limifolia, these two haworthias only rarely offset and grow very slowly, but with leaves that can be deep wine-red with blue tessellations, or almost purple-black, they’ve become popular in the relatively short time since they were discovered. Not particularly closely related, but equally rare in habitat, H. bruynsii forms tiny rosettes of brown, translucent leaves, and looks like a miniature form of H.retusa. It remains solitary, and in the wild it’s mostly sunken into the ground, its light-transmitting leaves usually coated with a fine covering of dust.
A number of the other species in the subgenus form chunky, stiff-leaved rosettes. Some of these, such as Haworthiascabra var. starkiana, grow in bright sun that turns them brilliant yellow-orange in the wild; someone once described its rosettes as resembling a cluster or small, upright bananas. As with many of these uncommon haworthias, the habitat of H. starkiana is better measured in acres than square miles. Growing in the same system of small canyons are its relatives, var. lateganiae and var. scabra, interesting, slow-growing plants whose rosettes, sadly, bear less of a resemblance to a bunch of bananas. H. longiana forms slow growing rosettes with narrow elongated leaves up to a foot and a half in length, while the even slower growing H. sordida puts forth small rosettes of rough textured sometimes recurved, green to blackish leaves. These plants will gradually offset. H.starkiana and its relatives grow into large clumps given enough time, but some similar looking species, such as H. glabrata (with smooth leaves) and H. glauca (usually with tubercles) grow and clump up more quickly.
The members of this subgenus mostly lack the immediate eye appeal of the stained-glass looking retusa forms, but many of them are among the more valued collector’s items in the genus and will reward careful observation. Most are fairly easy to grow. The farthest-eastern forms are better treated as summer growers, with weekly water spring, summer and fall and a partial winter rest, while the others do better with water once a week in spring and fall, every other week in summer or winter. As with all haworthias, maximum light, short of burning, will bring out the best in the plants, but most will survive in considerably less than optimum conditions without too much complaint.
The third subgenus, Robustipedunculares, consists of just a few species which produce larger (but still quite plain) flowers on long, often branching stalks. Most of these plants can become quite large and many remain solitary. They include H. pumila, the largest Haworthia, with rosettes up to nearly a foot across, and with often ornately tubercled leaves, glistening white and pearly, and in some forms, shaped like pearly, little glazed doughnuts. H. minima, slightly smaller, with some forms comparatively free to offset, also has pearly tubercles, sometimes arranged in orderly, shining rows, while in the somewhat larger, usually solitary H. kingiana the tubercles are flattened. Most forms of the last species in this subgenus, Haworthiamarginata, lack tubercles, and form large rosettes which, with their often sharp-tipped leaves, seem rather similar to some of the smaller, choicer agaves. Most of these plants remain scarce in cultivation, although hybrids with H. pumila in them are common enough, looking like larger, more striking versions of H. attenuata. The plants in this group grow in winter-rainfall areas, and can be fairly touchy in cultivation. I’ve seen H. pumila growing on steep hillsides, half-hidden by densely growing shrubs, and have also seen it growing quite exposed on level ground. As with so many of these plants the trick is to give the plants as much light as they can take without burning, plant them in fast draining soil that has some organic matter in it, and watch out for too much water in summer—every three weeks is probably a safe bet, with water once every week or week and a half in fall and spring and every two weeks in winter, providing there’s at least occasional sunlight.
Though not as immediately attractive as some of the other haworthias, the choicer members of these subgenera often appeal to more sophisticated collectors who appreciate their subtle interplay of geometry, pattern and texture, and can see them as unique living miniature sculptures.
The Garden has a good assortment of these other haworthias. A good number of accurately named, choice plants have bee acquired over the last few decades. We often have some of the faster growing ones for sale, and from time to time some of the slower types as well.
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