Mammillaria fragilis, or Thimble Cactus, is a clump-forming cactus native to Central Mexico. The clumps can exceed 12 inches (30 cm) in width in containers. Stems are up to 1 inch thick and are easily disarticulated. Tubercles are in 5-8 spirals with 12-16 white, radial spines, which are needle shaped and up to 5 mm long. The central spine are brown at the tips, pointed outward and very stout. This cactus is an easy one to grow and very showy in containers.
Blooming: In the greenhouse, our specimen blooms from late summer into fall, with very small pale yellow flowers about 1/2 inch (1.2 cm) long.
Culture: Mammillaria fragilis need full sun to light shade, with a well-drained soil mix. In the greenhouse, we use a soil mix consisting of 2 parts coarse sand to 1 part peat moss to 1 part loam with small gravel added to increase drainage. The cactus is well watered and allowed to dry thoroughly before watering again. We fertilize the plants only once during the growing season (usually in mid spring) with a balanced fertilizer diluted to 1/2 the strength recommended on the label. During the winter months, water is somewhat restricted. We never let the winter temperatures fall below 55°F (13°C) at night.
Propagation: Mammillaria fragilis is easily propagated by division of older clumps, from disarticulated pieces, and from seed.
Mammillaria fragilis was featured as Plant of the Week October 27-November 2, 2006.
Guide to Past Plants-of-the-Week:
Cal's Plant of the Week was provided as a service by the University of Oklahoma Department of Microbiology & Plant Biology and specifically the late Cal Lemke, who used to be OU's botany greenhouse grower and an avid gardener at home as well. If the above links don't work, then try the overview site. You may also like to look at the thumbnail index. ©1998-2012 All rights reserved.