Popular Types of Small Cactus
By J.W. Carpenter
, last updated August 4, 2011
An incredible variety of small ornamental cactus plants are available for both indoor and outdoor growing. While placement outdoors requires a warm dry climate, many types of small cactus can be grown indoors in containers or terrariums placed in a sunny window. If you live in cold northern climates with little winter sunshine to warm the windowsills, you can simply supplement the available sunlight with a cool white florescent grow light. Small cactus plants come in many great forms and shapes, and most produce exquisitely beautiful, brightly colored flowers each year. For more information on some of the most popular types of small cactus, read on.
Tom Thumb Cactus
The Tom Thumb cactus (Notocactus mammulosus) makes an excellent houseplant, as it prefers light shade environments. A very short column-shaped or globe-shaped cactus, the Tom Thumb reaches only 10 centimeters in height and about 7 centimeters in diameter. It features 18 to 20 vertically oriented ribs. Along each rib, spines emerge in clusters of about 10, producing a near complete spine covering over the body of the cactus. Several large, silky, pink and yellow flowers emerge in the spring. This is an excellent windowsill cactus, best planted in its own miniature pot.
Old Man Cactus
Old Man cactus (Cephalocereus senilis) is a popular houseplant specimen originating in Mexico. This columnar cactus is famed for its covering of long white wispy hair, which is reminiscent of an old, white-haired man. It is said that the covering of hair serves to protect the cactus from the intense glare of the Mexican sun. Though it can reach to 40-feet in height in its native habitat, the Old Man cactus grows exceptionally slowly indoors and retains a manageable size for many years. Note that this plant’s white hair hides many rows of sharp spines.
The Hedgehog Cactus (Echinocereus engelmannii) is a small outdoor cactus that produces brilliant-pink, springtime flowers followed by one-inch edible fruits. This is a columnar cactus that emerges in tightly packed clumps, usually numbering about 10 to 15. Though individual columns can exceed one foot, they typically reach no more than about six inches tall and several inches in diameter. As it common name implies, this cactus is covered with two to three inch long spines, which emerge all about the plant in clusters of four or six. This plant is best grown outdoors drier southern climates.
Star Cactus Species
Star cactus (genus Astrophytum) generally refers to a number of related species, including the Bishop’s Cap cactus (A. capricorne), the Sand Dollar cactus (A. asterias), and the Goat's Horn cactus (A. capricorne).
The Bishop’s Cap cactus takes a heavily ridged globe shape as a young plant, and an increasingly columnar shape as it ages. You can expect it to eventually reach about eight inches. This cactus has long, arching spines and produces an attractive gold-yellow flower in the mid-summer. Though it does well indoors, it has somewhat high sunlight requirements.
The Sand Dollar cactus, sometimes known as the Sea Urchin cactus, is a spineless cactus that usually takes a short globular form. Though it is quite rare in the wild, it is widely cultivated indoors. It produces a large, glossy yellow flower each year. In periods of drought, the Sand Dollar cactus flattens into a disk shape, looking something like a sand dollar.