Description
This peculiar plant is the result of crossbreeding between two of the most famous Astropytum myriostigma cultivars Astrophytum myriostigma cv. Kikko nudum and Astrophytum myriostigma cv. Koh-yo and shows some interesting intermediate features of both the parents. These hybrids have inherited by cv. Kikko nudum the unmistakable pointed tubercles along the ribs edges and by cv. Koh-yo the bright yellow and red stem that gradually turn to dark green. The colouring accentuates during winter dormancy and each individual plant has its own unique particular colouration. The flowers are also very beautiful. Usually the young seedlings appears nothing special and looks like normal myriostigma, and barely shows any trace of saw teeth, but they start to produce the distinguishing indentation and turn into an amazing colorfull adult as they get 3 to 5 years old. In general the bigger the “saw teeth” are and the longer and fatter they are, the better.
Stem: Pentagonal to almost spherical with pointed tubercles along the ribs edges, in fact its areoles stick out with large notches between them, giving them a saw tooth look. The furrows which appear transversely on the ribs cuts the continuity of the ribs and the plants appears decorated with a geometrical design which is raised above the surface. The stems is smooth lacking or mostly lacking white flecks and can be 5-10 cm in diameter. This is an odd Japanese variety with colourful bodies that take its name (Koh-yo) from the colours of the leaves in autumn. The old part of the stem is green, but new growth is bright yellow and red with a wide range of intermediate colours. This cultivar is not a variegate because the yellow and red colouring is not permanent, but occurs prevalently on the new growth near the stem tip and along the ribs, but gradually turn to dark green. The colouring accentuates during winter dormancy and is greatly influenced by cool temperature. In spring-summer the bright coloured areas fade and the plant takes a more uniform green appearance. The colouring not only varies during the year, but each individual plant has its own unique particular colouration.
Spines: None.
Ribs: Usually 5.
Flowers: Like those of the well known A. myriostigma, pale-yellow, shining-silk.
Blooming season: Spring to summer.
Origin and Habitat
Japan, Garden origin (Nursery produced cultivar)
Cultivation and Propagation
Variegated and coloured cacti are regarded as choice and difficult in cultivation, but despite that the Astrophytum myriostigma cv. Koh-yo are relatively easy to grow. They are sometime seen as grafted plants, but grow well on their own roots too.
Exposure: They cannot tolerate prolonged exposure to direct sun light (especially during the hottest summer days), so grow them in half-shade or under filtered sun.
Spoil: Use mineral well-permeable substratum with little organic matter (peat, humus).
Watering: Water sparingly from March till October and keep perfectly dry in winter at temperatures from 5 to 15 degrees centigrade. (In general these plants are more tender and cannot endure freezing temperatures ) In the rest period no high atmospheric humidity!!
Propagation: Almost usually by seed. Plants are often grafted onto column-shaped cacti.
