CoronaCactus Nursery LLC - Plant of the Month

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Cultivation Key

� Full sun/Bright shade�� Water sparingly

� Deeper pot for the taproot

Hardy to 5F (-15C) if completely dry! But safer around 40-50F (5-10C) in cultivation and kept dry.

Plant of the Month

May 2009

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Mammillaria theresea

Cactaceae (Cactus Family)

Form: Mammillaria theresea is usually a solitary bodied plant, but it can form clusters (especially when grafted). Globular in shape when young, although later becoming more cylindrical. It has an olive green body color with hints of red and purple. Its habitat is the Coneto Mountains in Durango, Mexico, at elevations of 2200-2300m. This is the only known location for this plant. However, its ability to retract itself into the soil during the cold winter or intense heat of the summer has made this plant difficult to locate when not in flower. This high elevation habitat also has large fluctuations in temperature. M. theresea can be found under snow and ice in the winter and submerged in puddles of water during the summer rains. M. theresea has been said to be hardy down to -15C! However, in cultivation and especially when grown in a pot, the plant needs to be very dry to survive temperatures that low. This plant does have a taproot, so a deeper than usual pot should be used.

Size: Typically growing to around 3-5 inches tall with stems around 1-1.5 inches in diameter. Solitary or in clusters.

Flowers/Fruit: The flowers of Mammillaria theresea are some of the most beautiful of Mammillaria flowers. Huge pink to violet petals on long funnel like tubes with yellow stamens and pale yellow stigmas. These are quite large for a Mammillaria, at nearly 1.5 inches across. The fruit of M. theresea are quite interesting. Termed: Cryptocarpic. This means they form and grow within the body of the plant. They do not protrude out. The fruit can stay within the body for several years. The seeds have inhibitors to stop it from germination within the fruit. In habitat, the thin membrane covering the fruit can split open and drop its seeds down at the base of the plant. Which can give the false impression that a single plant is clustering. The seeds can be extracted with great care using pointed tweezers. It�s best to wait a year or more to sow any freshly extracted seed. Fresh seed is difficult to germinate.

Sun/Water: Being a high elevation specie, M. theresea can take a lot of sun. However, it does not appreciate a lot of heat and can go into a short dormancy during the hot summer months. Water sparingly during the spring/fall and keep very dry during the winter and at any time summer dormancy is induced.

Propagation: Seed, offsets or grafting. Since the nature of this plant is to keep its seeds for itself, it�s not offered very much on commercial seed lists. More commonly propagated via offset cuttings or by speeding up its growth and forcing the production of offsets by being grafted.

Books/Websites: The Cactus File Handbook: Mammillaria is a great reference. Available through Rainbow Gardens Bookshop. An excellent Mammillaria website is: Mammillarias.net More websites can be found on our Reference Links page.