Introduction to Gasterias, Common and Easy Succulents for the Garden and PotteryBy Geoff Stein (palmbob)
July 4, 2010
In a previous article I discussed Aloes, and one of the Aloe relatives, Haworthias. Gasterias are also related to the Aloes, being in the same family. Which family they actually belong in depends a lot one what source you follow. Currently Davesgarden puts them in the Aloaceae, but nearly as many sources put them in Asphodelaceae. The World Checklist of Plants, a well respected English taxonomic resource puts these in the Xanthorrhoeaceae, which personally confounds me (Xanthorrhoaceae includes some amazingly dissimilar genera, with the main one being the Australian Grass Trees which look about as much like Gasterias as they do roses).
The common names of most Gasteria include names like Ox Tongue, Cow Tongue or Lawyer's Tongue (the leaves tend to look tongue-shaped, though not sure if they look more an ox's, cow's or even a lawyer's tongue than those of any other animal or profession.)
A general description of these South African natives is that they are succulent-leaved, stemless (most), rosettes or distichous (leaves in two ranks) in array, suckering with flattened, stiff, thick leaves ending in a gentle rounded end (few exceptions of course). Leaves are straight are slightly arching and vary in surface consistency to smooth and shiny (most common) to rough and sometimes even pebbly. Leaf colors range from dark green (nearly black) through various shades of dull green, to greys and are either mottled or, less commonly, striped or solid in color. They range in size from 2 to 3 centimeteters in diameter (or about the size of the average Haworthia species) to several feet in diameter (similar to a large aloe).
Several Gasterias in my garden
Gasteria roots are typically succulent and short and vary in thickness and numbers from season to season, particularly as temperature and moisture levels change.
Gasteria doreeniae (real name?) on left and Gasteria batesiana var. dolomitica on right showing root variations
The characteristic that sets these succulent plants apart from their relatives, the Aloes, Astrolobas and Haworthias are their flowers, the shape of which the genus is named after (gaster means stomach). The flowers dangle off a thin stem (called a scape) individually and are stomach shaped, with a large swelling near the flower's base and an arching curve near the tip where the reproductive parts can be approached.
Examples of Gasteria flowers (multiple species)
Though some species of Gasteria differ moderately in their inflorescence and flower shapes and sizes, unlike how most plants are accurately identified in the taxonomic world, it is not the flowers that distinguish most Gasteria species from each other. This is similar to the situation encountered when trying to speciate Haworthias though not quite to that extreme. Haworthias basically all have identical flowers, and most Gasteria species have fairly similar flowers. Fortunately there are perhaps about sixteen species of Gasteria so there is less confusion in this genus as there is in the Haworthias where there are many dozens of species, some which vary incredibly depending upon where they came from geographically and how they have been grown. Gasterias can be similarly confusing but I don't find them as frustrating as I do the Haworthias. But hybridization among, and variation within the species still make accurate identification a challenge sometimes.
In general, these plants are fairly easy to grow in cultivation and make excellent potted plants. Most grow well in lower light situations and so can perform fairly well as indoor plants as long as one is prepared to deal with the associated problems with parasites and fungus. Most Gasterias like a lot of light, though, and tend to be much healthier the more light they get, as long as it is not hot, damaging afternoon sun. I would not categorize these as sun-loving plants, particularly in my inland southern California climate, though there are certainly some exceptions.
Gasteria glomerata (left) fried after a nearby plant was removed exposing it to more sun. It eventually recovered by never looked great. Right photo is of Gasteria bicolor in my front yard that looks somewhat sad and stressed by the end of the summer, though it never burns like Gasteria glomerata does
Most Gasterias seem to do most of their growing when it is cooler, and grow quite well in winter even where there is a lot of rain (as here in Southern California). However in most of their native locations, winters tend to be more on the dry side. Water in the heat of summer, when most plants seem to be relatively inactive and have shrunken roots, can end up allowing these plants to rot, so careful when watering potted specimens during the warmer months of the year. Some are much more sensitive than others, though. I rarely see rot or any difficulties in my plants in winter, even if it's very cold and wet for weeks on end, and all my plants are outdoors in the garden or in pots. It is the summer when I manage to kill off most of mine.
Some Gasterias in my garden in partial to 3/4 shade. Note the top dressing. From left to right: Gasteria nitida var armstrongii hybrid, Gasteria glomerata, Gasteria carinata var verrucosa, Gasteria Van Damme Mutant and Gasteria ellaphieae far right.
Gasterias in community pot in winter in nearly full shade (left) and summer half day sun (a bit too much- right)
As with most succulents, Gasteria grow best in very well draining soils with a high mineral content with a lot of large diameter rock, sand or other porous or non-porous material. The exact makeup of the soil is not as important as its ability to drain water quickly, but retain at least some in the cracks and crevices. Soils should also be relatively high in oxygen content (in other words, have lots of spaces between the particles). Soils with a lot of peat, vermiculite, fine sand or organic material are more prone to allow rot to occur. Because of their small root structures, they are very easy to dig up and replant. Top dressing is always recommended, not only to improve water percolation, but to help hold the plant down into the soil. Fertilization should be light but can be very helpful during the cooler seasons. Water should be year round, but sparingly when it is hot.
Propagation is not my specialty but these are reportedly very easy plants to grow from seed as well as leaf cuttings (I think there needs to be some leaf base in the cuttings). Division of the entire plant or removing suckers is the easiest way to get more plants. Gently pulling plants apart rarely does any damage to these.
Control of bugs and fungi is of major importance in most growing situations that are not ideal. Black spot is a common fungus somewhat unique to this genus and though it is rarely dangerous for the plant, mars them by forming large, circular black spots or depressions in the leaves. Control with rose antifungal products. It is unclear under what conditions this disease is most common and it seems to show up out of nowhere on the nicest, healthiest specimens sometimes. Mealy bug is another common attacker, particularly in low light situations. Most over the counter insecticides will get rid of this, and just hosing with water will, too, but it is a sign your plant probably wants more light.
outdoor plant showing fungal spot on leaves
There are between 16 and several dozen species of Gasteria, depending upon who you read and it is unlikely the number will ever be agreed upon by everyone anytime soon. The following are some of the more distinctive of the species:
Gasteria acinacifolia is one of the larger species and a good one for landscape use in a Mediterranean climate. It grows up to several feet in diameter and forms large colonies of rosettes formed by long, stiff, thick lancelote leaves that taper to a point (without the classic round-tipped leaves some other species have). The leaves are heavily speckled with white and are smooth.
Gasteria acinicifolia close up (left) and growing in full sun in Huntington Gardens in winter (flowering) in southern California
Gasteria batesiana is a smallish species with very rough-surfaced lancelote to wedge-shaped leaves that form a rosette in a mature plant. There are often bands of mottling giving the leaves a subtle striped look. In cross section the leaves are nearly triangular with a keel on the underside and the top being flat or even somewhat fluted (theoretically to funnel water to the center and down to the roots during periods of very low rainfall).
Gasteria batesiana outdoors in Huntington Gardens
Several show plants of Gasteria batesiana, southern California
Gasteria baylissiana, in contrast, is a very slow-growing, smaller plant with fat, thick pale, rough-textured pale grey to grey-green arching leaves. This is one of the rarer species and old clumping specimens are costly and make wonderful potted show plants.
Gasteria baylissiana photos
Gasteria bicolor is is a typical and common species, and also a variable one with several recognized forms and dozens of synonyms. Usually this plant is dull, dark green with lots of pale spots. The leaves are shiny, stiff, tipped with a tiny point and usually remain distichous even with age (though this one suckers aggressively so quickly forms a large clump of distichous plants). Gasteria liliputiana is a smaller form of this and very popular in the nursery trade, though I find this form a bit touchy outdoors (rots easily and burns in sun easily).
Gasteria bicolor photos
another form of Gasteria bicolor on the left, and Gasteria bicolor var liliputiana on right (leaves about 1/3 to 1/4 size)
Gasteria carinata is a small to medium sized plant with spotted lancelote leaves. Gasteria carinata var verrucosa (more commonly known as Gasteria verrucosa) is the most popular form with the leaves being completely covered with white tubercles, and in some forms, the tubercles forming ornamental stripes of white bumps over both the ventral and dorsal surfaces.
Gasteria carinata 'regular form' on left the much more popular Gasteria carinata var. verrucosa right
Gasteria carinata var verrucosa in the garden (left) and being sold as Gasteria verrucosa (right)
Gasteria croucheri is one of the larger species and adults look quite similar to a fat-leaved aloe. The leaves are lancelote, smooth, somewhat mottled and usually taper to a point but with a bit of the classic Gasteria rounded leaf tip, too . There are no teeth on the leaves, something most aloe species have. These are often solitary plants, but can form small colonies.
Gasteria croucheri in my garden (left); exceptionally colored (stressed) specimen in plant show (right)
Gasteria ellaphieae is one of my personal favorites and I have found this to be a reliable, slow grower but an excellent landscape and potted plant. The leaves are grayish, arching and heavily but finely tuberulated. It is a very neat plant forming elegant compact colonies of grey, rough leaves. It is somewhat rare compared to most other Gasteria species.
Gasteria ellaphieae in my garden (left) and nice show plant on right
Gasteria glomerata is is another of my favorite species and is and easy to tell apart from the others with its diminutive size, pale green, rough arching leaves and intense suckering behavior. This plant looks great when in fills a pot or small, tight space in the garden. It is not a good plant for full sun, though and I have blanched many of these trying to get them to adapt to such situations. The flowers of this species are somewhat different being nearly completely red orange (not as bicolored as most Gasteria flowers are). It is a fairly common and easy to grow species.
Gasteria glomeratas in my garden
Nice show plant (left) and plant blooming in winter in my front yard (bit too much sun- blanched a bit)
Gasteria nitida var. armstrongii (aka Gasteria armstrongii) is one of the more popular species to grow and show. It is fairly common as well, but so slow growing that specimens filling an entire pot are rather old and quite ornamental. This species has very thick, dark green to nearly black leaves that are smooth and lumpy at the same time. Gasteria nitida is a very different looking plant and I often wonder how these two could be related.
Two nice show plants of Gasteria nitida var armstrongii
Younger specimen yet to sucker (left) and a nice variegated show plant (right)
Gasteria rawlinsonii is a unique looking species that grows in un-Gasteria-like tall, distichous columns of dull green, arching rough leaves. The first few times I saw large specimens of this plant I did not think it was a Gasteria. I find it a bit tougher to grow (easy one to rot), but I have since learned to mostly ignore it rather than water it and I have better success. In nature this is a cliff dweller and is the only Gasteria that typically grows down (hanging by its roots). I have not tried to grow it this way, but I do have one in hanging pot and it is growing laterally rather than upright so far. It is a very slow grower. It also does not like full sun much.
Gasteria rawlinsonii in show (left) and in my garden (right)
two shots of larger hanging plang showing some spiraling (some plants will do this, or this could be a hybrid).
There are several to many other species of Gasteria (see below) but I either don't know much about them or are more unclear how to tell them apart from each other.
Gasteria decipiens (left) Gasteria disticha (right)
Gasteria excelsa photos (some sources do not list this as a separate species)
large landscape specimen (nearly three feet in diameter) of Gasteria excelsa
Gasteria pillanii shots
Gasteria obtusifolia (left) Gasteria pulchra (right)
Gasteria vlockii in show
Below are some known and some unknown (by me) Gasteria hybrids (intrageneric)
Gasteria 'Hogwarts' Gasteria 'Hyashi Hybrid'
Gasteria 'Little Warty' (a very common and popular hybrid- left) Gasteria 'Nishi' on right
Gasteria 'Uyehara' in show southern California
Rest of above Gasteria are unknown hybrids
Gasteria readily hybridize with both Aloes and Haworthias (though I have not seen too many of the latter). Some of these hybrids are among the most popular and commonly grown of all the Aloaceaes and several can often be picked up at major garden outlet centers. In general, these plants are far more hardy in terms of dealing with full, hot sun as well as overwatering, which is perhaps why they are so popular.
Gasteraloe 'Green Ice' (a very common and easy hybrid)- left; Gasteraloe Wart Hog right
left is a very popular Gasteraloe which is often confused with Aloe aristata which is the aloe it is hybridized with- very easy and aggressive grower; right is Gasteraloe 'White Wings' in plant show
Gasteraloe flower showing it has characteristics of both (shape of Aloe, color of Gasteria); right is another Gasteraloe but don't know the name
These are Gastwarthias (Gasteria x Haworthia) 'Royal Princess', the most popular and common of such a hybrid
nice variegated Gastwarthia in plant show
For more on Gasterias, see PlantzAfrica.com