Plants will endure twenty degrees of frost without injury; where the winters are colder than this, protection must be given or the plants must be grown under glass. They grow readily from seed in sandy or clay loam in pots or flats, with just enough water to keep the soil moist, not wet. Large plants transplant with difficulty; the roots should not be injured in digging, and the plants should be set in gravelly clay and watered occasionally during dry spells.
Slender Pincushion Cactus (Mammillaria fasciculata—Mammillaria Thornberi)
(Named fasciculata from its habit of growing in clumps; Thornberi in honor of one of the authors of this book, who rediscovered it)
How to identify and how it grows
The Slender Pincushion Cactus grows in the form of slender stems in dense clusters of fifty to two hundred plants of many sizes, all crowded closely together. The stems are four to seven inches tall, and an inch or so in diameter. They seem to be thickened a bit in the middle and taper off toward the bases and tips. The tubercles are arranged in eight to twelve spiral rows, all less than a quarter of an inch long, and somewhat four-angled in shape. The flowers are an inch or more wide and as long, with the inner petals broad and acute and of a purplish pink color. The fruit is club-shaped, a half-inch or so in length, and of a scarlet hue.
How to grow
This Pincushion is difficult to transplant. Plant in partial shade or in the protection of shrubs in very sandy soil. Water frequently to keep the soil barely moist. It is best set in clumps as it grew in the field. The plants will endure twenty to twenty-five degrees of frost without injury; with colder winters they must be protected or grown under glass or in conservatories.
Cream Pincushion Cactus (Mammillaria Johnstonii)
(Named for Ivan M. Johnston who collected the plant in Sonora)