Description
The cultivar ‘ONZUKA’ (In Japanese speaking “Onzuka Ranpo-gyoku”) has snowy-white, heavily speckled epidermis with fabulous markings much like the ‘kabuto’ ’ asterias. The white marking varies considerably from plant to plant and there exist an enormous number of different designs, and also plants change their appearance in age and they are full of surprises as they grows. The “tricostatum” is a strikingly pretty cultivar with only three ribs and the “columnaris” deviate from the well-known typical form for its more columnar growth and smaller flowers size.
Stem: Slender and more thin, already in the youth phase. Dimension 25-50(-100) cm tall, only 3-5(-8) cm in diameter.
Ribs: 3.
Flowers: Usually smaller than those of Astrophytum myriostigma, 2,5-4 cm in length, pale-yellow, silk-shining, occasionally with an orange gloom. The flowers arise from the areole at the tip of the stem on mature plant (at least 4-5 years old).
Blooming season: Blooming intermittently throughout the warm months from spring to autumn.
Remarks: This cultivar tends to be unstable, and some of the three ribbed specimens develop additional ribs as they age. Old and big plants which maintain the typical three ribbed shape are very very prized.
Origin and Habitat
Garden origin (Nursery produced cultivar)
Cultivation and Propagation
Although regarded as a choice and difficult plant in cultivation it is relatively easy to grow. It is sometime seen as a grafted plant but grows very well on its own roots too. Use mineral well permeable substratum with little organic matter (peat, humus). The Astrophytum myriostigma grows much faster with a low nitrogen content fertilizer in spring and summer. Water sparingly from March till October, the thin, fibrous roots suffer if there is humidity, therefore the plant should be watered only when the surrounding terrain is dry. Keep dry as soon as the temperature starts dropping in October and keep it perfectly dry in winter at temperatures from 5 to 15 degrees centigrade. (but it is Hardy to -7°C for short periods) Although it is one of the easier Astrophytum to grow, they tend to rot at that time of the year, if kept wet. In the rest period no high atmospheric humidity!!
Sun Exposure: Light shade to full sun, its colour tends to richer and darker when grown in light shade.
Propagation: They can be propagated easily from seed or graft. Seed Collecting: Allow unblemished fruit to ripen; clean and dry seeds. Properly cleaned, seed can be successfully stored. Plants are sometimes grafted onto column-shaped cacti. Cutting scions from a flourishing plant is almost a crime because the scions do not root easily.
