Astrophytum myriostigma 'Onzuka'
Astrophytum myriostigma 'Onzuka is a prized Japanese-bred selection of the bishop's cap cactus (Astrophytum myriostigma), selected over generations for its exceptionally dense, bright-white flecking, arranged in bold, striking patterns across the body — making it one of the most coveted lines within the species.
Care follows that of the parent species, Astrophytum myriostigma; see that article for full cultivation detail. This page covers only what sets 'Onzuka' apart.
Description
Like a typical bishop's cap, 'Onzuka' is a spineless, ribbed cactus — usually with the classic five ribs, though four- and multi-ribbed plants occur — that forms a rounded to columnar body as it ages. What distinguishes the 'Onzuka' line is its trichome flecking: the small tufts of white woolly trichomes that speckle the epidermis of all myriostigma. In ordinary plants this flecking is scattered and fine, but in well-selected 'Onzuka' plants it is remarkably dense and brilliantly white, so that it can nearly cover the green skin. Growers select and cross the best individuals to concentrate these traits, often arranging the flecking into bold bands, swirls, or near-solid white coverage.
Because 'Onzuka' is a breeding line rather than a single clone, plants vary in quality. The finest examples show thick, snow-white flecking with high contrast against the dark body; lesser seedlings revert toward ordinary myriostigma patterning. Selecting from a reputable source, or picking standout individuals yourself, is the surest way to obtain the character the name promises.
Cultivation
Grow 'Onzuka' exactly as you would the parent species — see Astrophytum myriostigma for the full picture. In brief: give it bright light, a fast-draining mineral mix, sparing water with a full dry-down between drinks, and a dry, cool winter rest above freezing.
One practical note for this cultivar: bright light helps bring out and maintain the dense white flecking. Plants grown too dim tend toward a greener, softer look with less pronounced woolly patterning, so err toward a well-lit spot (while still shading from the harshest afternoon sun to avoid scorch on an unacclimated plant). As with all Astrophytum, overwatering and a soggy mix are the main killers.
Propagation
'Onzuka' is raised almost entirely from seed, with growers crossing their best flecked parents to push the line further. Seed-grown plants show natural variation, so save seed from — and select among — the most heavily flecked individuals. Slow or difficult seedlings are sometimes grafted onto a vigorous stock to speed them along, after which they can be grown on their own roots.
See also
- Astrophytum myriostigma — the parent species, with full care detail
- Astrophytum — the genus overview
- Propagation — seed · Grafting · Soil and potting mix · Watering