I’ve had mixed results with genus Astrophytum. I’ve lost some of these cacti to mysterious, chunk-devouring pests—I suspect rats, but it could be squirrels or birds. I’ve lost others to rot… perhaps underwatering, dead roots, and then rot growing on the dead roots.

This individual Astrophytum cv ‘Onzuka’ is doing really well so far. It overshadows its 3-inch pot with a full 3.5-inch diameter. I’ll repot it soon. I’ve heard from an advanced grower that he cuts off the taproot at a certain age, forcing the stem to grow smaller, less rot-prone roots. Sounds radical but I seem to recall he claimed everyone in Japan does this.

It’s hard not to like Astrophytum cv ‘Onzuka’. It has strange, white-speckled skin, its body is oddly geometric, and its flower is understated but beautiful.

Speaking of Japan, that’s where this justifiably popular cultivar of Astrophytum myriostigma is said to originate.

You won’t find a blue-flowered cactus—the entirely family Cactaceae famously lacks blue flower pigment. Green cactus flowers, however… while not common, green cactus flowers do exist, for instance on this week’s South American cactus, Gymnocalycium leeanum.

As it matures, this Argentina cactus often forms clumps of several round bodies. Its central spines (outward-facing spines) may be lacking, as in the pictured specimen. The radial spines are held close to the round body, as if ironed flush to the cactus’s outer surface.

Gymnocalycium leeanum flowers range from yellow, yellow-white, or greenish yellow, as in the plant pictured.

Gymnocalycium leeanum, grown and photographed by Mr Sentient Meat

Bolivian cactus Rebutia neocumingii was known under genus name Weingartia from its description by Backeberg in 1950 until Weingartia was combined under Rebutia by Hunt in 1987. Its flowers can be yellow, orange or red depending on locality. It’s normally solitary and unbranched, though the individual pictured is sprouting additional heads. Typically this species has much longer spines; this plant was obtained as form brevispina. It is about 7.5 cm across; at full growth, it can reach 10cm across and up to 20cm in height.