By Timothy J. Malinich
Cacti (singular cactus) catch the eye of many hobbyists. They are easy and rewarding to grow, fun to display, and readily available. People are often hesitant to grow them because they fear the reputation of these desert denizens. Here are a few tips that will hopefully de-mystify the collecting of cacti.
Names given to cacti tend to create confusion for the collector. Common names used by hobbyists often include entire groups of related plants. For instance, the genus Gymnocalyciumhas about 71 species, but they are all referred to as “chin cactus” for the dimple between each cluster of spines on the rib.
Each cactus does have its own scientific name, listed as Genus species, where the genus is general and the species more specific. Even that has gotten confusing as taxonomists (people who identify, describe, and name plants) have reclassified hundreds of cactus species. Growers, collectors, and suppliers may or may not adopt those changes, so you may find two or three scientific names referring to the same plant. When you research plants, look for synonyms of the name in the listing.
Cactus hobbyists quickly run out of room for their collection. Consider the size of the plants as your interest sharpens; think of how it might fit into your home or greenhouse. Many of the globose plants, such as Gymnocalycium, will remain small their entire life. A 30-year-old G. horstii can still be less than 10 inches tall and 6 inches wide. Columnar cacti, such as Cephalocereus or Cereus, however, can reach heights of 50 feet and will outgrow a typical indoor ceiling within 10 years.
Cleistocactus and Oreocereus are also tall columnar cacti, but more manageable in size. In cultivation, they may reach several feet in height; difficult to manage, but still possible. Clump-forming plants, such as Opuntia(prickly pear, bunny ears) or Mammillaria, are manageable as far as height, but will need room to spread as they mature.
Cacti prefer very well-drained soil. They have a limited root system that cannot handle large amounts of moisture. A small root system in a large pot and a soil mix that holds plenty of moisture will create ideal conditions for root rot. Choose a pot that seems too small for the cactus you are planting. A pot that is only 2 inches wider than a globose (short and round) plant is large enough. If you want to plant a group of cactus plants, keep each one in its individual pot and use filler, such as stone, between the pots in the planter.
Use pots that have drainage holes. Either clay or plastic are fine. Clay is more forgiving of overwatering, as it will dry out faster; if you tend to overwater, go with clay pots. Plastic is cheaper, cleaner, and can help hobbyists that might not be able to keep up with watering. As your plants grow taller, you will notice that they become top-heavy and tip over easily. Clay pots can add more weight to the base for top-heavy plants.
Choose the planting medium carefully; even those listed as cactus soil might not have enough grit to provide good drainage. You can make improve a mix by adding perlite, grit, coarse sand, or pumice to improve its drainage. A mixture of 3 parts good potting soil and 1 part extra drainage material is a good place to start. In nature, cacti grow in a mixture of rock, grit, silt, and some organic matter. After planting you may have to use stakes or rocks to hold the plant upright until it roots into the new pot.
Fertilizer and Water
There is this misunderstanding that cacti like to be starved and dry. They are desert plants, but they do have a season during which they grow and reproduce. The goal of the grower is to keep them dry and dormant in the off-season, but provide ample water and nutrients during their growing season.
If you don’t have a greenhouse, this means gradually moving the plants outside in the spring after the danger of frost. Cacti will do just fine with regular watering and fertilizing during the growing season. Use a water-soluble fertilizer mixed just under full-strength. Slow-release fertilizers are even better, but put them down early in the season according to label directions.
As fall approaches, gradually let the plant dry and move it to its overwintering location. During the winter, only water enough to keep the cactus from shriveling; depending on conditions, this could mean a small drink every few weeks – never soak the roots during dormancy.
Spines provide the texture and interest that attracts a collector to a plant. But no matter how careful you are, you will likely get an occasional puncture from your plants; many punctures if you are not careful.
Spines grow from the same area that would normally produce leaves. They grow from their base (like your fingernails) and push new spine outward from the base. If you look closely at a large spine you can see the growth ridges running across the spine.
Barrel cactus (Ferocactus) grows a thick coat of large spines, making them unapproachable from any angle. Each spine is capable of inflicting a deep puncture wound. Mammillaria have a central spine with a hook on the end. They are fairly flexible and won’t readily pierce skin but will hook onto clothing or hair. Opuntia produce thousands of glochids – clusters of very small spines that break off and stick to skin. Their small size makes them difficult to remove and they can be very irritating, as hundreds can bury themselves in your flesh at the lightest touch.
Tools for handling cacti vary from grower to grower. Several layers of folded newspaper can be wrapped around a cactus without damaging the spines too much; corrugated cardboard also works. There are also reinforced gloves made for working with thorny plants.
There are many great resources available to the cactus hobbyist that provide much more detailed information about individual plants and cultivation than this article has room for. If you have an interest in cacti or succulents, join one of the many associations across the country.
The Cactus & Succulent Society of America (CSSA) publishes a great journal for hobbyists. Their website, cssainc.org, has a list of state and international affiliates.
With a little research and understanding, it is easy to quickly develop a great cacti collection. This is the year to get hooked by cacti.