Astrophytum ornatum

Astrophytum ornatum, called the bishop's cap or monk's hood cactus, is a flowering plant of the family Cactaceae that is endemic to the Central Plateau of Mexico. It is the largest and tallest species of the genus Astrophytum. A solitary, cylindrical plant, it can reach about 2 metres in height and 30 centimetres in width on the plateau, and it develops numerous white woolly flakes that help protect it from the sun. It flowers through the summer, bearing canary yellow flowers 7 to 8 centimetres long. In cultivation it is described as rugged, resistant to root rot and easy to grow in well-drained soil, and an established plant tolerates cold down to about minus 4 degrees Celsius. It has been given the Royal Horticultural Society's Award of Garden Merit.