Astrophytum asterias 'Nudum'
Astrophytum asterias' 'Nudum is a cultivated form of the sand dollar cactus, Astrophytum asterias, distinguished by a smooth, glossy green body that lacks the fine white woolly scales (flecking) typical of the species. Because the flecking-free trait breeds true and combines cleanly with other selected characters, nudum plants are prized as breeding stock and form the basis of many smooth-bodied selections.
Description
The nudum form shares the flattened, disc-shaped, ribbed body of the parent species, but its skin is bare — a clean, even green with a slightly waxy sheen rather than the dusting of white scale-tufts (trichome flecking) that gives ordinary A. asterias its speckled, greyish appearance. The pale, felted areoles sit in a neat row along the crest of each rib, and the plant remains completely spineless. Flowers are the familiar silky yellow with an orange-red throat. Removing the white flecking makes the underlying rib structure and areole placement much easier to read, which is one reason breeders like to work with nudum stock — desirable body shape and rib symmetry are on full display.
The nudum trait is a base condition rather than a single showy feature: growers cross it into other selections to produce smooth-bodied versions of already-refined lines. In these combinations the glossy green surface sets off contrasting characters such as heavy woolly areoles or reshaped ribs.
Cultivation
Care is the same as for the parent species; see Astrophytum asterias for the full account. In short, give it bright light with some protection from the harshest afternoon sun, a fast-draining mineral mix (see Soil and potting mix), sparing water with a complete dry-down between soakings, and a dry winter rest above freezing (see Watering).
One practical note for the nudum form: because there is no white flecking to reflect sunlight, the bare green body can be a little more prone to scorching if moved abruptly into strong sun. Acclimatise plants gradually and they colour up to a healthy deep green. As with all A. asterias, avoid overpotting and keep the mix lean to hold the low, flat habit.
Propagation
Nudum is grown and perpetuated chiefly from seed, and it is as seed parents and pollen donors that these plants earn their keep. The flecking-free character is inherited, so controlled crosses between nudum plants reliably yield smooth-bodied seedlings, while crossing nudum into flecked lines lets breeders recombine it with other traits over subsequent generations. Choice or slow seedlings are sometimes grafted to speed them along, as with the species generally.
See also
- Astrophytum asterias — the parent species
- Astrophytum — the genus overview
- Grafting · Soil and potting mix · Watering · Propagation — seed