Mammillaria erythra f. ruber
M. erythra is native to Mexico Central, Mexico Gulf and Mexico Southwest where the plant grows on lava rocks in a humus rich substrate and can spread up to 1850 m of altitude. The “ruber” form has been collected by Werner Reppenhagen and the plant grows on crevices filled with humus, in lava rocks.
M. erythra is an attractive cactus belonging to the Cactaceae botanical family. The plant has a solitary habit and can reach up to 9 cm in height and 30 cm in diameter. The stem is globose, made of quadrangular, pyramidal tubercles and hollow at the apex. The epidermis is dark green but in the wild it can take on reddish shades when exposed to the direct sunlight. The tubercles are woolly at the apex, produce latex and bear the spines. The radial spines are short, pointed, straight, needle-like, brownish and 1-8 in number. The central spines are 1-4 and are similar to the radial ones but with black tips. Blooming occurs from the spring to the early summer and the flowers are borne at the apex of the tubercles. The flowers are funnel-shaped, diurnal, arranged in a circle around the stem, they are dark carmine to magenta with brownish midveins. The cactus doesn’t bloom frequently, but when it does it produces small, club-shpaed, magenta fruits. When the fruits ripen, after 5 months, it is possible to harvest the brown and flattened seeds, generally fertile. The ruber form is larger than the normal one and with redder hues.
The plant has a slow growth rate but it easy to cultivate. The best sun-exposure is in bright place but is recommended to avoid direct sun-light in the hottest periods. The minimum temperatures that the plant can withstand are 5° C, below this temperature it begins to suffer so it needs to be placed indoors in the coldest periods. The perfect soil is a well-drained soil that let the water to drain away and avoid root rot. To achieve this feature, you can mix the pumice soil, clay and soil. Remember to use a perforating pot to drain excess water. Watering can be done regularly in Spring and Summer: during the vegetative period you can water the plant (every 7 days), checking that the soil is completely dry before watering again; in winter you should stop the watering to allow the plant to enter dormancy. If you want a faster and lush growth you can fertilize the plant once a month during the growing season with the specific fertilizers for succulents; stop fertilizing throughout the winter. If the pot starts to be too small for the plant you can repot the plant in a pot 2 cm wider. Repotting should be done early in the growing season with fresh new potting soil. Be careful to red spiders and mealy bugs.
Propagation can be done by cutting or by seed. By cutting you can make the cut during the spring and then let the cutting dry; after a few days the cut surface will dry and a callus will form, then place the cutting in a mixture of sand, soil and pumice. To increase the success of propagation you can make two or more cuttings at the same time. For cuttings it is recommended temperatures around 20 °C. By seed it is very simple to propagate the plant, it is enough to sow the seed in a sandy loam soil and keep it with a high level of humidity and at temperature of 14 C°.
The name of the genus come from the Latin word ‘Mammilla’ that means ‘teat’ or ‘nipple’. The name “ruber” refers to the plant’s tendency to take on red hues and the color of the flowers.
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