Mammillaria densispina aka Mammillaria Densispina

Mammillaria densispina is a small cactus from Mexico. It grows slowly and lives for many years. It belongs to the cactus family, Cactaceae. Kew places its range in northeast Mexico, reaching Michoacán. Records also span several states in central Mexico. These include Guanajuato and Jalisco. It grows at heights of 5,740–9,840 feet [1,750–3,000 metres]. Wild plants grow on large rocks and volcanic soils in oak woods. Kew also links this species with desert and dry shrubland.

The plant most often forms one round stem. With age, this can take the shape of a short cylinder. It reaches about 0.39 feet [0.12 metres] tall. Its usual upper width is 0.20 feet [0.06 metres]. Larger stems can reach 0.33 feet [0.10 metres] across. A thick coat of spines hides the dark green stem. Short, thick bumps called tubercles cover the stem beneath the spines. These bumps have a cone shape. Their axils, or joints, have wool when young, then turn bare. The tubercles do not give off milky sap.

Each spine group has 20–25 or more thin radial spines. These stiff needles vary in length and spread outward a little. Their shades range from glassy white to pale yellow or brown. Five or six stronger central spines grow from swollen bases. These spines start with a red tint, then turn yellow. Their upper parts often stay dark brown. This dense coat of spines adds much to the plant’s appeal in cactus collections.

Small flowers shaped like funnels open in spring. Their insides are pale yellow. The outsides may have yellow, orange, or purple tones. Long fruits follow, in greenish-pink or cream shades. The reddish-brown seeds have an egg shape. Their narrow end lies at the base. Older plants may form clumps with offsets near the base. These small new plants offer a way to grow more besides seed. Detach offsets once they reach one-third of the parent plant’s size.

When grown in gardens or pots, this species needs strong light and good airflow. Use a mineral-rich potting mix that lets water drain with ease. Added pumice or perlite can help water pass through. Water during summer, but wait until the soil feels dry. Then soak the mix and let it dry again. Keep the plant dry through winter. Its small root system makes excess water a concern. Wet soil can lead to root rot. Too much water and shade can cause swollen growth with a poor shape. Use a feed high in potassium during summer as part of this care routine.