Mammillaria leptacantha a tiny usually unbranched or slowly clustering cactus, deep-seated in substrate and inconspicuous. M. leptacantha stems are usually globose to short, cylindrical, green, 12-13 cm tall, 5-6 cm thick.Tubercles are conical to cylindrical. Radial spines are about 27-30, radiating, finely bristly, needle-like, white to golden yellow, 4 - 6 mm long.
Flowers are diurnal, purple, generally with darker midribs, up to 15 mm long, blooming in summers.
A slow-growing species, Mammillaria grows without difficulty when supplied with a required amount of water and ventilation. Plant loves full sun or afternoon shade, inside it needs bright light, and some direct sun. Direct sun encourages flowering and heavy spine production.
Requires excellent drainage provided by a very permeable open cactus soil (With not less than 50% grit content). Avoid the use of peat or other humus sources in the potting mixture.
Watering needs to carefully monitored and only done when the soil is dry to touch and not in the winter season. If kept outside it requires the afternoon shade, and bright light if kept inside.
Enrich the soil using a fertilizer rich in potassium and phosphorous, but poor in nitrogen, because this chemical element doesn t help the development of succulent plants, making them too soft and full of water.
It is an excellent plant for garden rockery settings, desert type landscapes, patios and botanical gardens
For watering cacti, the golden rule is to make sure the soil is completely dry before watering! This will stop the roots from rotting. It is advised to always use a pot with a drainage hole so that excess water can get drained out. If kept in a sunny area, you will need to water it once every week. If it is in a semi shaded or filtered light area, you might need to water it once in 2 weeks.
Cacti like soil that is well aerated and fast draining. You can fertilise the cactus in the summer months when it is in its growing season. During the winters it is best to cut back on any fertiliser and let the plant rest.