Tom Thumb Cactus (Parodia mammulosa) Indoor Care Guide

Tom Thumb Cactus, botanical name Parodia mammulosa, is a small cactus found in the wild throughout Brazil, Argentina, and Uruguay.

This cactus is prized by landscapers and gardeners for its small size and interesting shape. Tom Thumb Cactus grows slowly and can reach a height of only about three inches. The stem is short and globose, topped with bright yellow, funnel-shaped flowers.

Flowers are almost as tall as the cactus itself (about 3″) and serve as the headlight feature of this cactus. Around 18 to 20 ribs cover the green stem sporting sharp spines that can easily cause injury on contact, so handle with care.

Tom Thumb Cactus is a popular plant used in rock gardens, succulent gardens, or as a houseplant. It is tolerant of neglect and can withstand periods of drought. However, it will produce more flowers and grow more vigorously if given regular water during the growing season.

This cactus should be protected from frost to prevent damage to the leaves.

Parodia mammulosa Main Characteristics

Common Name	Tom Thumb Cactus, Lemon Ball Cactus
Botanical Name	Parodia mammulosa
Synonyms	Echinocactus mammulosus Malacocarpus mammulosus Notocactus mammulosusRitterocactus mammulosus
Family	Cactaceae
Genus	Parodia
Type	Cactus
Native Range	Brazil to Argentina
USDA Hardiness Zones	9b to 11b
Mature Size	up to 6 inches
Bloom Time	Summer
Foliage	Evergreen
Propagation methods	by seeds, by cuttings
Sun	Full sun
Soil	Well-drained
Toxicity	Non-Toxic

Tom Thumb Cactus Care

If you are looking for a small, attractive cactus for your home or garden, Tom Thumb Cactus is a great choice. With its ease of care and interesting appearance, this cactus will add beauty to any space.

Light and Location 

Tom Thumb Cactus grows best in full sun but can tolerate some light shade if the sun gets particularly harsh. In its natural habitat, it is often found on rocky hillsides or grasslands. When grown indoors, place your cactus near a sunny window. A cactus grown without enough direct sunlight will be unnaturally green and be prone to root rot.

Watering

Tom Thumb Cactus is drought tolerant and can survive long periods without water. However, it will grow best if given a deep watering every two to three weeks during the growing season. Allow the soil to dry out completely between waterings. During the winter months, reduce watering to once a month or less.

Temperature

Parodia mammulosa is native to South America and can withstand warm temperatures. Therefore, it can be outdoors year-round in USDA hardiness zones 9b to 11b. If you live outside these zones, bring your cactus indoors during the winter months to protect it from frost damage. As long as temperatures remain above freezing and your cactus is dry, it will be fine.

Humidity 

Parodia mammulosa prefers low humidity. If the air is too humid, it can lead to root rot. If you live in an area with high humidity, place your cactus in a well-ventilated location and grow it in a pot with drainage holes to allow excess moisture to escape.

Fertilizer

Tom Thumb Cactus doesn’t need much fertilizer to thrive. If you choose to fertilize your cactus, use a light application of cactus food every two to three months during the growing season. Be sure to follow the directions on the fertilizer package, as too much fertilizer can damage your cactus.

Propagating Parodia mammulosa

Tom Thumb Cactus can be propagated by seeds or cuttings.

To propagate by seeds:

1. Sow the seeds in a pot filled with a cactus mix or fine sand.
2. Cover the pot with plastic wrap to create a mini-greenhouse and place it in a warm, sunny location.
3. Keep the soil moist but not wet and wait for the seeds to germinate, which can take two to four weeks.
4. Once the seedlings are big enough to handle, transplant them into individual pots filled with a cactus mix.

To propagate by cuttings:

1. Take a cutting from a healthy part of the plant using a sharp knife or garden shears. 
2. Allow the cutting to callous over for several days before planting it in a pot filled with a cactus mix. 

Place the pot in a warm, sunny location and keep the soil moist but not wet. Once the cutting has rooted, it can be transplanted into an individual pot filled with the cactus mix.

Potting and Repotting Tom Thumb Cactus

Tom Thumb Cactus can be grown in a pot or planted in the ground. If you live in an area with cold winters, it’s best to grow your cactus in a pot so that you can bring it indoors when the weather gets chilly.

Repotting is seldom needed as these are small cacti that remain small throughout their lifetime. Even at their largest, they can easily fit the role of a desktop plant. In addition, these are slow growers that require a bit of time to come into their own.

Remember that soil nutrients deplete over time. So even if you feel the root ball is snug inside its pot, if the plant has been in the same pot for over five years, it’s time for a fresh batch of potting mix.

When potting or repotting, use a pot with drainage holes to allow excess water to escape. Choose a pot that is only slightly larger than the root ball of your plant. Tom Thumb Cactus doesn’t need a lot of space to grow, and too much room can lead to problems with watering.

To repot, carefully remove your cactus from its current pot and loosen any roots that are bound up. Plant it in the new pot and backfill with the cactus mix. Water well and place the pot in a sunny location.

Common Pests

Parodia mammulosa is susceptible to mealybugs. Mealybugs are small, wingless insects that feed on plant sap. They can be difficult to control and, if left unchecked, can kill your cactus. If you see mealybugs on your cactus, treat them with insecticidal soap or neem oil.

Tom Thumb Cactus (Parodia mammulosa)- Care Tips (Video)