The thimble cactus – Mammillaria gracilis [mam-mil-AR-ee-uh, GRASS-il-is] is an attractive succulent native to Central Mexico.
The Mammillaria plant genus has around 300 species of highly variable forms.
A highly prized cactus succulent among collectors and gardeners, mammillaria gracilis fragilis is loved for their desirable traits in cultivation, visually appealing appearance and are generally treated as houseplants.
These unique cacti are small in height, but since they grow in a cluster they add color and beauty to your garden experience.
Commonly known as thimble cactus, mammillaria gracilis fragilis – or mammillaria vetula – features creamy yellow flowers.
While the bloom time of these succulents is summer, expect to see lovely and eye-catching yellow flowers in winter as well.
Besides being called thimble cactus, mammillaria gracilis is generally known by the common names:
- Powder Puff
- Powder Puff Pincushion
Mammillaria Gracilis Fragilis Care
Size & Growth
If kept in the right conditions, thimble cactus grows robustly.
It produces small, round-shaped offsets which form a cluster around the parent plant.
Densely covered in white, silky hair, the body of the plant has a broad appearance and usually a green/blue color.
This cactus looks like a powder puff, as the radial spines densely cover the small globe.
For those who know the art of growing cactus and succulents, they will find thimble cactus to be an easy plant to grow in a window with lots of sunlight and will definitely add this cactus plants in their wishlist of plants they want to grow.
A mature thimble cactus mammillaria is around 3″ to 5″ inches high and normally 3″ to 4″ inches in diameter.
For best results, provide plants with good airflow.
Flowering and Fragrance
A beautiful, small cactus with a cylindrical body, Thimble cactus Mammillaria produces small yellow or white flowers, often found in a halo or circular shape.
For better flowering, allow plants to enjoy a cooling period in winter.
During this time, suspend watering altogether.
Unlike other cactus, the Mammillaria has tubercles from which the flowers emerge from the axle of these tubercles.
Light & Temperature
Thimble cactus thrives in full sun and bright light.
Even though most Mammillaria species prefer strong light, some cannot survive more than four hours of direct sunlight.
This small cactus grows well in temperatures between 70° and 80° degrees Fahrenheit (21° – 27° C) and become dormant in winter.
During the winter, keep colorful potted cactus plants on a windowsill as houseplants.
When the temperatures drop to somewhere between 60° and 65° degrees Fahrenheit (15° – 18° C), the plant will bear flowers.
Move the plant outside during the summertime for the best results as the season marks its bloom time.
They survive well in USDA hardiness zones 8 to 10.
Watering and Feeding
In the winter, when the plant turns dormant, suspend water. However, mist occasionally.
For the rest of the season, water the plant thoroughly.
Between waterings, allow the soil mix to become dry.
Don’t expose the plant to prolonged dampness or let it sit in water for long periods.
For feeding, fertilize the plant with a cactus fertilizer mix during the growing seasons.
In the dormant winter period, suspend the feeding as well.
Soil & Transplanting
The plant requires porous cactus soil and grows well in a rich, fast-draining cactus soil mix with a pH range between 6.1 and 6.5.
Some plant types will require a gritty succulent or cactus potting soil for the best results.
Grooming and Maintenance
The plant is a low-maintenance small cactus and grows in clusters.
Covered in interlaced white spines, these dense clusters gradually form large mats.
Since thimble cactus plants are not cold hardy, give them lots of sun on a windowsill protected from the elements.
Its grooming is simple.
Keep an eye on any rot and cut rot out quickly.
In case the plant becomes overcrowded, repot as needed.
However, when repotting make sure all rotted or dead roots are removed.
How To Propagate Thimble Cactus
Thimble cactus is propagated easily with the help of its offsets.
- Carefully remove these offsets and let them dry on a paper towel for a couple of days.
- NOTE: Bare root plants are available online
- Wait until callus forms over the cut surface.
- Take a new pot, and place the new plant in it by using a cactus potting soil mixture.
- Keep the new plant in a warm place.
- Don’t repot the plant in a regular container until new roots begin to emerge.
Thimble Cactus Pest or Disease
Mammillaria cactus grown as a houseplant often contract bacterial or fungal diseases, often caused by excessive watering.
This is why it is important to stick to a strict watering schedule.
It also makes it all the more essential to observe the plants for any signs of rot.
These rots often appear as black spots around the base of the plant.
In addition, thimble cactus is susceptible to pest attack.
The common pests are:
It sometimes gets difficult to control these pests as they are too tiny and can easily hide in the plant.
One way to control these pests is by using a diluted rubbing alcohol solution.
Learn more about Controlling Succulent Pests here.
Mammillaria Gracilis Uses
The thimble cactus is usually used as a decorative houseplant in colder regions.
In late winter, it flowers creamy yellow flowers, enhancing the indoor look of any house.
Since it grows in a cluster, it is also well suited in fairy gardens.
Mammillaria are low growing, fast-spreading plants and make a wonderful addition to rock gardens, and cactus gardens.