Growth Habits: The plant is small, globular to cylindrical. The epidermis is an olive green with tinges of red. It usually gets to just over 1in.(3-4 cms.) high and 1in. (3 cms.) in diameter. The many tubercles are small and cone shaped and the areoles are woolly. The radial spines vary from 20 to 30 and are white to yellowish, soft and thread-like and form a very attractive pattern. There is no central spine.
Scientific name: Mammillaria theresae
Common name:
Synonym: Mammillaria saboae var. theresae
Etymology: The genus name Mammillaria is taken from the Latin mammilla which means “breast, teat, nipple” and refers to the small tubercles (fleshy lumps or warts) covering the plant body. All cacti in this genus are rib-less
The species name theresae has been named after Theresa Bock who, together with her husband John, discovered the plants on the Coneto Mountains in Durango, Mexico, in 1996
Origin: Found in the Mexican state of Durango in the Coneto Mountains. ( Sierra Madre Occidental)
Light: Requires good light but if the sun is too fierce the epidermis tends to take on a very red colouration. When this occurs it is probably a good idea to allow the plant some shade for half a day.
Compost: The plant seems to prefer a mineral based potting mix. One that is fairly rich in nutrients and well drained.
Water: The plant is very sensitive to too much water and should be watered quite sparingly during the growing season and kept completely dry during the winter.
Flower: The flower is pink and unusually long-stemmed for a Mammillaria (3.5 cm in diameter and up to 5 cm long). The stigmas are pale yellow
Fruit: Mammillaria theresae is one of the few cacti with cryptocarpic fruit. Cryptocarpic means that the fruit and seeds stay within the body of the plant. When the flower drops off the body of the plant closes over the fruit and the seeds ripen within the body of the plant. The seed then stays within the body of the plant for several years or even until the plant dies. A close look in the lower axles of the plant will sometimes show the lozenge shaped mark where the old flower dropped off. A careful ‘poke’ to break the membrane will usually release some seeds. With this plant old seeds germinate much better than new ones. This is the direct opposite of what usually happens, i.e. fresh seed are normally better than old ones.
Min. temp: A safe temperature is 45°f.-50°f. 8°-10°c. Although the plant is said to be able to withstand some frost, I personally would not like to chance it.
Cultivation: Mammillaria theresae is not the easiest of Mammillarias to keep (and many growers graft them to give themselves a better chance of keeping them healthy). It is not however as difficult to keep as some of its close relatives for example Mammillaria goldii. As we have already said it requires a mineral soil that is well drained and very careful watering.
Habitat: It grows mainly in patches of moss on rock formations on the eastern slopes of the Coneto Mountains and at altitudes of around 2200-2300 m. The mountainous habitat is characterised by serious fluctuations in temperature.
Comments: This is certainly an unusual looking Mammillaria and is well worth growing for the flowers alone. The first flush usually come in early spring and if you are lucky the plant will flower at least twice more through the summer. The flowers are plentiful and unusually large for a Mammillaria. Even when not in flower the plant is very attractive. In the wild the plant in periods of drought contracts and pulls itself under the ground, making it virtually impossible to find.