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Tiny Little Barrels
Still another group related to the large Mexican barrel cacti,
the plants for this month mostly live in and around the Chihuahuan
desert. In contrast to the big barrels, however, the various
species found in Turbinicarpus, Epithelantha,
and Pelecyphora include some of the tiniest cacti,
with hardly ever reaching more than a few inches in diameter.
Among these tiny plants we can find some of the most fascinating
cacti, some widely known and appreciated, while others remain
rare novelties. There’s a good possibility as well that
new species remain to be discovered.
The
same conditions of arid habitats and extremely localized distribution
that distinguish many of the species of Thelocactus,
Neolloydia and Gymnocactus apply—often
to an even greater extent—to most of these miniature cacti
as well. Though the overall range of Turbinicarpus
encompasses much of northeastern Mexico, many of the individual
species grow only on one or two isolated hillsides, their extreme
endemism bringing up questions of what does exactly constitute
a species. A considerable number of plants once considered distinct
species have been reduced to subspecies, while others are now
simply considered forms of no taxonomic significance whatsoever.
Although reasons for their odd distribution remain somewhat
unclear, it is clear that populations of plants separated from
other populations will in time differentiate; whether and when
that difference merits taxonomic recognition is an issue for
botanists and not for cactus plants to determine.
As mentioned in my previous article, the plants of Gymnocactus
currently fall within an expanded definition of Turbinicarpus,
but the turbinicarpus discussed in this column don’t resemble
the gymnocactus types very much at all. These “classic”
Turbinicarpus grow either into little rounded cones
or remain squat and round, like small flat-topped discs. Many
of them have a gray epidermis, and all of them have highly modified
spines. The species concept known as Turbinicarpus schmiedickeanus,
now divided into eight quite distinct subspecies, includes plants
of both forms. Among the more elongated ones we find ssp. gracilis,
a particularly tiny plant with tubercles that almost align themselves
into rows, tipped with a single long, flexible, non-threatening
spine. Subspecies schmiedickeanus itself, along with
the yellow flowered ssp. flaviflorus and the white
flowered ssp. dickisoniae, also elongate into approximate
cones with spines that range from hair-like to thick and corky.
The plants aligned with T. pseudomacrothele also tend
to grow into little elongated globes with pointed tubercles.
The largest of these is T. pseudomacrothele ssp. krainzianus,
up to two inches tall, nearly as thick, and prone to slowly
grow into a small cluster of stems, while ssp. lausseri,
at about half that size (and with flowers twice as big), may
be the smallest. Other turbinicarpi with either elongated tubercles
or elongated bodies (and so little known in habitat that they
currently retain their status as separate species) include T.
laui, T. hoferi, and T. swabodae, along
with several species and forms even newer to cultivation. For
horticultural—not botanical—purposes, a second group
of turbinicarpus can be distinguished because of the plants’ flattened tops, with tubercles only weakly visible. This group
includes relatively common plants such as T. schmiedickeanus
ssp. macrothele (and its slightly darker-skinned neighbor,
T. “polaskii”), T. lophophoroides,
and T. schwarzii, as well as relatively rare plants
such as T. jauernigii and T. rioverdensis,
with its two flattened central spines holding themselves close
to its flattened top of the plant and resembling miniature cow
horns. These plants all look a bit like Lophophora williamsii
(peyote) in both shape and color (though the presence of spines
and absence of wooly tufts give them away), which no doubt accounted
for some of their early popularity among collectors.
Half way between the two growth habits we find plants such as
T. schmiedickeanus ssp. klinkerianus and the still
rarer T. alonsoi, with bodies that essentially are
disc-shaped and flat on top, but that also have prominent tubercles
rising above the general level of the plant body. And finally,
in a group all by themselves, are two species that over the
years have been shunted from genus to genus, at times being
placed in Thelocactus, Pelecyphora, Neolloydia,
Gymnocactus, and their own temporary genus, Normanbokea.
Now presumably permanently ensconced in Turbinicarpus,
these two species, T. pseudopectinatus and T. valdezianus,
have taken the neotenous (retention of juvenile characteristics
into adult development) tendencies of the genus even further.
In contrast to the soft hairs, corky bristles, and flattened
strips of the other species, the spines in these plants amount
to tiny, flat, white sunbursts in T. valdezianus, and
symmetrically arrayed ellipses roughened by minute ridges in
T. pseudopectinatus. The defensive potential of the
spines of the other turbinicarpi seems dubious enough, but in
these two species the reduced spines are utterly harmless and
barely recognizable as spines at all. T. valdezianus,
a plant with a large range in comparison to most turbincarpus
species, lives in appropriately barren limestone dominated deserts
where it hides between rocks, but T. pseudopectinatus,
though seemingly equally designed for the most arid of habitats,
grows farther to the east, on the down slope of the Sierra Madre
Oriental, where it lives in relatively well watered terrain,
in rich, black soil mixed with limestone chunks, among low-growing
Brahea palm species.
Turbinicarpus as a genus has evolved into a survival
strategy of quick growth and early sexual development (hence
its neotenous habit—the retention of seedling characteristics
into adulthood, which makes the plants look as cute [cactus-wise,
that is] as puppies and kittens). The plants grow easily and
fairly swiftly from seed, and since they’re not very hard
to grow if given good drainage, bright light, a somewhat lean
mix and very dry winters, they’re quite common in cultivation.
In spite of this, many of them come from habitats probably better
measured in square yards than in acres or square miles, and
a good number are potentially under threat of extinction in
their native land.
Resembling the most highly adapted species of turbinicarpus,
the two valid species of the genus Pelecyphora have
evolved quite a different means of survival. From the southern
reaches of the Chihuahuan desert, pelecyphoras are extraordinarily
slow growing. The plants, with rock-hard bodies, display their
reddish purple flowers considerably less freely than do Turbinicarpus,
and they are not as easy to grow from seed either. In habitat,
at the very top of low limestone hills, where the drainage is
fastest, they can attain a reasonably large size (big, fifteen
or more-headed specimens of P. asseliformis can reach
six or seven inches in diameter), and we can only guess at the
age of some of these plants; fifty years? A hundred? More? Pelecyphora
asseliformis is covered with spine clusters reduced to
little, flat-topped, barely ridged lozenges (looking something
like a miniaturized mammoth tooth), with absolutely no ability
to repel predators, but quite capable of brewing up other defenses.
The plants manufacture complex, bitter-tasting alkaloids that
can send would-be predators on an unexpected, and possibly even
fatal trip. The second species, P. strobiliformis,
with a body composed of the overlapping scales of its reduced
tubercles, and spines even more reduced to a couple of almost
invisible bristles at the tips of the scales, looks like it’s
covered with upside down shingles. It’s a little quicker
growing than its cousin and doesn’t get as large; nonetheless
it is equally bizarre and at first sight seems as much a thing
carved from stone or wood as it does a living plant. In the
wild both of these plants live mostly underground, with just
a bit of their totally flat tops protruding above soil level.
Seed grown P. strobiliformis tend to elongate and develop
rounded tops, but P. asseliformis is more likely to
retain its shape, although its growth rate is painfully slow.
The third member of our trio of genera is Epithelantha.
Although these tiny plants range as far south into Mexico as
do the others, they also grow in the northernmost stretches
of the Chihuahuan desert realms, for example, in rocky settings
on the outskirts of Carlsbad Caverns, New Mexico. Rather than
bizarre, intricate sculptures, these little cacti resemble miniature
golf balls. They generally are quite round, although sometimes
with flattened tops, and are totally covered by clusters of
generally pure white spines, which are so tightly attached to
the epidermis of the plant as to render it completely invisible.
In a few of the forms some of the spines stick out at an a great
enough angle from the plant body to make it seem a little bristly,
but in most the spines don’t resemble spines at all, just
a barely roughened white coating. Epithelantha bokei,
the species most resembling a golf ball, remains solitary north
of the Rio Grande, but can grow into small clusters south of
the river in Mexico. The widest distributed species, E.
micromeris, survives high altitudes in New Mexico and Texas,
and harsh deserts in the Mexican state of Coahuila. Other forms,
such as the densely clustering E. pachyrhiza, and the
very attractive E. unguispina, with more bristly, black-tipped
spines, (both currently considered subspecies of E. micromeres)
are more localized. The majority of epithelanthas eventually
grow into small or even medium sized clumps, while others remain
solitary. In the wild they sometimes live among blocks and plates
of pure white limestone, barely peeking out from under the flattened
rocks, and, as a result, can be quite difficult to find. Besides
looking like a golf-ball, to a considerable degree epithelanthas
also mimic the dried deer dung that shows up in even the driest
desert regions, a resemblance with perhaps more survival value
than the golf ball appearance.
The taxonomic placement of Epithelantha is not quite
clear, with the plants having properties associated both with
the larger barrel cacti, and that group of cacti related to
the very large genus Mammillaria. Their bright red,
thin fruits do resemble those of mammillarias, but even if they
are somewhat misplaced in the Echinocactus group, in
habitat choice and growing requirements they are close to these
other tiny barrels.
All of these plants need the brightest light possible, an extremely
fast-draining soil mix (I like to add some lime-based product,
such as oyster-shell or dolomite to the mix), and somewhat less
water than most cactus (I tend to water many of these plants
only every ten days or two weeks even during their growing season.
Other growers may be more generous with their watering, and
if given more water and slightly lusher conditions, the plants
will grow faster. They may also rot faster, particularly in
our humid winters). In winter the plants essentially need complete
dryness, especially in our humid climate; they certainly can
go for several months without any water at all during their
dormant period. Pelecyphora grow much more slowly than the other
genera, and may be a little fussier about excess water and humidity
as well (particularly in winter). As a result they’re
considerably rarer in cultivation than Turbincarpus,
with Epithelantha being somewhere in the middle in
terms of growing needs, growth rates and rarity in cultivation.
Cacti that don’t look like cacti have great appeal for
many of us, and all of these plants generally are cherished
by their owners. Obviously unsuited for outdoor gardens, these
extraordinary miniatures nonetheless make great subjects for
slightly adventurous growers.
The Garden has some nice Pelecyphora and Epithelantha,
and a good selection of Turbincarpus (though we don’t
have many of the newer species). We often have various Turbincarpus
species available for purchase at plant sales. |
