Cacti and succulents are the stars of the houseplants world at the moment. Most are easy to care for and have architectural appeal; that is their bold shapes and colors make them fun to decorate with. The differences between the two are more important to botanists and horticulturists than, uhhh…, real people. Succulents are plants that have modified parts (leaves, stems) that are designed to store water and reduce water loss during dry conditions. Cacti are succulents that are members of the cactus plant family (the Cactaceae), which like all plant families, is based on similarities in flower structure. Cacti are only found in the New World—the Americas, while succulents occur worldwide, with some of the most interesting coming from Africa. All cacti are succulents, but not all succulents are cacti. Most cacti have swollen stems and temporary or no leaves, while many of the other succulents have fleshy leaves.
Most cacti and succulents do best in high light. These are plants that want to be in your sunny windows. In low light they will stretch, and will probably lose most of their lower leaves, assuming they have them to start with. Christmas Cacti come from jungle habitats, and they are happy with bright light rather than hot sun. Plants have some ways of protecting themselves from high light intensities: they may develop red pigment or a waxy coating that makes them look silver or blue. This adds to their appeal. If you are growing them for their great look on the coffee table, place one there and a second in your window for better light, and rotate them once a week. That way, they will look better longer.
Cacti and succulents do need water from time to time. In the ground, they will develop wide-ranging, often shallow root systems that allow them to take advantage of both downpours and the occasional light shower in soil that drains and dries out quickly. In a pot, they just have a small root system that is totally dependent on you. I recommend watering once every couple of weeks in the spring, summer and fall, and entirely stopping your watering in the winter for cacti, and cutting back to once a month on the other common succulents, assuming normal household temperatures. It’s better to err on the dry side than to be too nice.
Fertilize with a fertilizer formulated for cacti (we sell several), which will be relatively low in nitrogen, to reduce soft, floppy growth that can be caused by a high nitrogen fertilizer regimen. Follow the label instructions, and remember that they are written for plants in ideal conditions with high light. Reduce feeding in lower light conditions.
Ouch! What about all those spines on the cacti and some of the other succulents? They are literally a pain. The prickly pear cacti (Opuntia; usually with flat pads) have a secondary type of spine called a glochid. These are like tiny hairs, and they are irritating and require a tweezers to remove from your skin, so be very careful around them; all you have to do is brush against them and you will be very unhappy. Otherwise, use caution and you should be fine. If you are transplanting, you can pick up small cacti with what I call “hot dog tongs.” For larger plants, take a piece of newspaper and roll or fold it into a strip about an inch thick and one or more inches high, long enough to be convenient to hold. Wrap it around the plant like a sling and you can pick the plant up without getting stuck. If weeds like oxalis become an issue, you might try weeding with a tweezers, or if it gets bad, knock the plant out of the pot and remove the soil with the weeds, and repot with fresh soil. This is more likely to be a problem outdoors or in greenhouses than in the average home.
Some of the succulents have sap that can be irritating or poisonous, so when working with them, you want to be wearing eye protection and gloves (e.g., Nitrile gloves) to protect your skin.
For you outdoor gardeners, there are cacti and succulents that are winter hardy in our area. Yucca and some of the prickly pears come to mind. Our former Prince George’s County Extension Agent, Bob Stewart, at one time had a nice cactus garden at his home, all perfectly happy in our Maryland winters.
For more information, think about joining the Cactus & Succulent Society of Maryland, which meets at the Cylburn Arboretum in Baltimore.
by Larry Hurley, Behnke horticulturist