About Mammillaria
Mammillaria is a genus of cactus that is native to North and South America. There are over 300 species of Mammillaria, according to the Cactus and Succulent Plant Mall. These plants are commonly known as nipple cacti because of their raised tips or tubercles. Mammillaria plants thrive in arid environments with temperatures above 50 degrees Fahrenheit (10 degrees Celsius) and plenty of light. Gardeners can grow Mammillaria indoors or outdoors in the garden.
Mammillaria plants belong to the Cactaceae family, which is characterized by succulent stems and spines. They are generally small plants that often form clusters or mounds. They have delicate-looking flowers that bloom in spring and summer. The flowers range in color from white to pink, red, yellow, green, and purple, depending on the species. The petals can be flat and spread open like a star or closed up like a bell. Mammillaria blossoms also have a pinwheel shape with multiple radial patterns that resemble spokes on a wheel or rays from the sun.
Unlike many types of cacti, Mammillarias do not have long protective spines that can injure humans or animals who come into contact with them.
Growing Mammillaria
Light
Mammillaria plants need plenty of light to grow well. If you live in a southern state with hot summers, choose an area that gets morning sun but will be shaded during the heat of the day to protect your plant from sunburn. If you don’t have access to shade in your garden, you can also grow your plant indoors near a large window that gets plenty of light but not direct sunlight. If your plant doesn’t get enough light, it will become pale and start leaning toward the nearest light source.
Soil
Mammillaria plants require well-drained soil, as they prefer dry conditions. These plants do not tolerate excessive moisture. You can use a commercial cactus mix for growing these plants, or you can make your own mix by combining equal parts of potting soil, sand, and small pebbles. You should spread a 1-inch layer of gravel on the surface of the soil as this will help prevent excess moisture and rot.
Temperature
The ideal temperature for a Mammillaria plant is around 15-20 degrees Celsius (60-68 degrees Fahrenheit) during the day and around 10 degrees Celsius (50 degrees Fahrenheit) at night.
Potting Size
As a general rule, pot up cacti in pots no more than 1-2 inches larger than the previous pot. You want to avoid going too big too fast as it could shock the plant and cause damage to the roots. Also, keep in mind that over-potting can cause an abundance of new growth. This may sound like a good thing but it’s actually bad because if you don’t have enough sun exposure or proper care, it will cause your plant to become leggy with weak stems that are prone to breaking easily.
Caring Mammillaria
Watering
The Mammillaria requires very little water once it has established itself in your garden or flower pot. However, if you notice the soil has dried out completely between watering, increase watering frequency slightly. The Mammillaria grows best when allowed to dry out between watering — so do not water this plant every day. Overwatering can kill your Mammillaria due to root rot. During the winter months when growth slows down considerably, allow the soil to become completely dry before watering again.
Fertilizing
Apply a balanced 20-20-20 fertilizer once or twice each month during the spring and summer months when plants are actively growing and producing flowers. Use only half-strength fertilizer and do not fertilize over winter when growth slows down considerably.
Repotting
Repot the Mammillaria plant every two to three years, or when it has become root-bound. Spring is the best time to repot this plant. Water the Mammillaria well a few days before repotting to reduce stress on the plant and avoid root rot.
Propagating Mammillaria
The Mammillaria is a cactus that can be propagated easily by seed and offsets.
Propagating by Seeds
You can propagate Mammillarias by seeds. Seeds must be kept warm and moist until they germinate. They’ll need a minimum soil temperature of 65 degrees Fahrenheit and a maximum temperature of 80 degrees Fahrenheit. Once the seeds sprout, they can be planted in a container filled with potting soil. When new growth appears, you can transfer the seedlings to their pots.
Offset Propagation
Offset propagation of Mammillaria is the simplest way of growing new plants. The offsets are detached from the parent plant and planted in a new pot with fresh soil. Offsets sprout at the base of the main plant, usually in clusters. These offsets can be removed any time of year but should be given two to four weeks after being removed to callous before planting.
Pest and Disease Control
Most Common Pests
The most common pest of Mammillaria is the Mammillaria moth caterpillar. Small colonies of these caterpillars can be removed by hand. The adult moth lays its eggs on the cactus pad, and when they hatch the larvae feed on the plant tissue. These caterpillars are usually at the base of a plant so check there regularly for their presence if you have a problem with them in your area. If you can’t remove them by hand then I recommend a biological control consisting of predatory nematodes that attack insects living in the soil.
Mealybugs are another pest that can infect Mammillaria plants. They cause white powdery spots on the pads and may be found under the ‘wool’ at the base of the plant. Spraying an insecticide soap or a horticultural oil onto mealybugs will kill them, but repeated applications may be needed to completely eradicate this pest.
Most Common Diseases
Bacteria: Cacti are rarely affected by bacteria. They generally show up as watery soft spots that turn black and dry out over time. This is more common in plants that have been exposed to too much moisture and also when the temperature is too cold. Some bacterial infections can be treated with antibiotics such as Streptomycin or other fungicides.
Fungi: Fungal diseases are more common than bacterial problems and most often occur in plants that have been exposed to excessive moisture or poor air circulation. Some fungal infections can be treated with fungicides such as Captan or Benomyl.