Prickly Pear Cactus
The prickly pear cactus (Opuntia) is among the most widespread cactus genera in the U.S. With over 100 species, this plant is characterized by its spiny, flat, club-shaped pads. Many varieties have large, round spines, while others have tiny, hair-like barbs that detach upon contact. While cacti are generally known as warm-weather desert plants, there are some prickly pear species that are hardy as far north as USDA zone 4. Prickly pear is best planted outside in the spring after the threat of frost has passed. Some prickly pears produce fruits that are prized for their edibility, but the plant's growth rate is fairly slow and it can take three or four years before a new plant starts fruiting.
Prickly pear and other cacti go dormant in winter, and their pads appear to dry up or deflate. They will return to their normal plumpness in spring when you can prune off any unsightly pads or deformed growth.
As a desert cactus, prickly pear thrives in full sun. That means at least six hours of direct sunlight per day. Indoors, a west- or south-facing window works best. In very hot climates, some shade during midday can prevent scald.
The most important requirement for any plant in the Opuntia genus is soil that drains well. Prickly pear easily grows in sandy or gravelly soil, but it can tolerate other soil types as long as there's good drainage and not too much water.
Prickly pear likes dry conditions, and very little watering is required to maintain the plant. This is why the cactus is often used in low-water gardens. Limit your watering to every two to three weeks or whenever the soil is completely dry. When watering, simply moisten the soil without soaking it. If you get minimal rainfall, that's often all the plant needs.
When growing prickly pear as a landscape plant in regions that get lots of rainfall, it's critical that the soil be extremely porous and well-draining.
Temperature and Humidity
Prickly pear cactus thrives in hot, dry desert summers. But many of its species have good cold tolerance. (Remember, desert nights can be cool.) It generally does well in regions that have mild winters and hot summers with low humidity. Prickly pear can struggle in areas that have very high humidity, even if the temperature is to the plant's liking.
Typical indoor temperatures and humidity levels are usually fine for a prickly pear grown as a houseplant. However, keep the plant away from heat and air-conditioning sources, as they can cause extreme temperature fluctuations.