Parodia buiningii aka Notocactus Buiningii

Parodia buiningii is a small cactus in the Cactaceae family. Its native range runs from southern Brazil into northern Uruguay. Kew places the Brazilian range in Rio Grande do Sul. It grows in a subtropical climate. The name Notocactus buiningii refers to the same species. This plant usually grows alone rather than forming a clump. It rarely makes offsets, so growers raise it from seed.

The stem forms a low ball, often with a flattened top. It reaches about 0.26 feet [0.08 metres] tall. Its width can reach 0.39 feet [0.12 metres]. Stem colours range from pale grey and blue-green to emerald green. The top lacks a woolly cover. About 16 sharp, straight ribs run along the body. Thin, blade-like tubercles stand between the spine-bearing areoles. Young areoles have wool, which they lose with age. Each bears three or four stiff central spines in a cross. These pale yellow spines have dark brown bases. Two or three shorter radial spines grow beside them.

The large, pale yellow flowers bloom in summer. They open by day and shut at night. Each flower can reach 0.26 feet [0.08 metres] across. This makes the flowers large beside the small stem. Their glossy petals surround a red-violet stigma. Thick brown wool covers the flower tube and pericarpel. The plant also bears hairy fruit that lengthens at the base. Fruit can reach about 0.10 feet [0.03 metres] long. The dull black seeds have a helmet-like shape. Tiny bumps cover their surface.

LLIFLE describes this cactus as easy to grow. It prefers cool conditions and a short winter rest. Give it full sun or light shade. Avoid harsh, hot sun during the middle of summer. Water it regularly in summer, but less often in winter. Winter watering should keep the roots from drying out completely. Its small root system suits a shallow pot. Use gritty compost with a slightly acid to neutral pH. LLIFLE also suggests an occasional dose of chelated iron.

The green ribs, pale spines and large blooms provide ornamental interest. The main stated growing risk is rot in cold, wet compost. The plant may also lose roots during winter. It can withstand light frost, but the evidence gives no precise temperature limit. No supplied source establishes its edibility or safety for people or pets.