Houseplant enthusiasts continually look for different and more exotic specimens for their collections. Fortunately, beginners and experts can find many good choices among the cacti and succulents.
The term succulent refers to a broad, loose category of plants, including cacti, which have developed thick, fleshy leaves or stems. These serve as water storage organs to ensure survival under arid conditions. Succulents are found worldwide. Besides cacti, they include many familiar plants: Jade Plant (Crassula ovata), Snake Plant (Sansevieria trifasciata), Medicine Plant (Aloe vera), Century Plant (Agave americana), Flowering Kalanchoe (Kalanchoe blossfeldiana) sold as gift plants as well as the Stonecrops (Sedum sp.), and Hens and Chicks (Sempervivum sp.) so common in the perennial garden.
The cactus family has nearly 2,000 species, with one exception, all native to the Americas. They range from the Arctic Circle to the mountains of Chile but are most abundant in the southwestern United States and Mexico. Cacti can be tall and thin or squat and spherical, frequently without branches and almost always without leaves. These shapes result in a large proportion of internal tissue to the external surface area, reducing the amount of moisture lost through the plant. They often have scales or spines ranging from microscopically tiny to wickedly large and barbed. These protect against predators and are thought to aid the plant in withstanding the hot, drying rays of the sun.
Many cacti and succulents are extremely well adapted to living in houses with low relative humidity (10 to 30 %). They require only modest amounts of water and fertilizer but need abundant light. Therefore, they should be placed in a bright sunny window. Insufficient natural light can be augmented by artificial lighting. A cool white fluorescent tube or a combination of daylight and natural white fluorescent tubes will give good results. Position them 6 to 12 inches (15 to 30 cm) above the plants and keep them on for 14 to 16 hours each day.
In nature, most cacti and succulents are found growing in well-drained sandy soil. These conditions should be duplicated indoors. A mix of one part potting soil and one part coarse sand is usually porous enough. A good test is to moisten the mixture and squeeze it in your hand. On release, the soil should fall apart. Both pot and growing medium should be sterile. Ideally, these plants should be grown in pots with drainage holes because excess water trapped in the soil will result in rotting and decay in a very short time.
During the low-light winter months, cacti and succulents should be watered only enough to prevent shrinking and withering. When watering, do it thoroughly. Water should flow through the drain holes, and the excess should be discarded after a few minutes. A series of repeated shallow sprinklings often results in distorted growth. As the amount of light increases in the spring, so does the plant's need for water. The soil should always be allowed to dry out completely between waterings.
Cacti and succulents have relatively low nutrient requirements. Cacti need fertilizer only once or twice a year during the late spring or summer when they are actively growing. Use a houseplant food higher in phosphorus than nitrogen, diluted to half the recommended rate. Other succulents may be fertilized in the same manner three or four times during the brighter months.
You may be able to bring your cacti and succulents into bloom indoors if you can approximate their native winter conditions. This involves a combination of good light, dry soil, and cool nights. Often a windowsill location will give the necessary light and cool night temperatures. Some cacti that are relatively easy to flower indoors are species of Mammillaria, Gymnocalycium, Echinopsis, and Rebutia.
Many cacti and succulents benefit from spending the summer months outdoors. Once the weather warms up, they should be placed in a semi-shaded protected area of the yard and then gradually moved to a sunnier location. Avoid locations where they will receive the hot, intense sunlight from 11 AM to 3 PM. Once outdoors, these plants will require more water, and so should be checked regularly.
Often, cacti and succulents are grouped in shallow dish gardens. While this may be an extremely attractive display method, several precautions should be taken. First, choose plants compatible with the growth rate so that one or two plants do not outgrow the rest. Even more important, the plants must have similar water requirements. Generally speaking, most cacti need less water than other succulents. Since these shallow dishes seldom have drain holes, it is essential that the plants are not overwatered. Broken clay pot shards or coarse gravel at the bottom of the container may provide a bit of drainage, but excess moisture will eventually be drawn back into the soil, which may keep the roots wet for too long.
Cacti and succulents are not troubled much by pests. If they have mealybugs or scale, the problem can be controlled by wiping them off with alcohol-dipped cotton swabs. Fungal or bacterial rots can almost always be prevented by maintaining adequate cultural conditions, light, and proper watering.
Cacti and succulents can be propagated easily by stem cuttings. Many succulents will form new plants from leaves that have been broken off. Allow the cutting wound to air dry before sticking the cutting into slightly moistened, sterile sand. Water sparingly since moisture retention is not a problem. When the roots have formed, transplant them into the regular sand and potting soil mixture.
- Succupedia: Browse succulents by Scientific Name, Common Name, Genus, Family, USDA Hardiness Zone, Origin, or cacti by Genus