Desert cacti care: light, water, and pet safety

Cactaceae (Mammillaria, Opuntia, and others)

Care table

Light	Some direct sun. Direct sun. A south or west window. Pale stretched growth means too dim.
Water	Let it dry out fully. Water when the soil is dry all the way down.
Humidity	Average room air is fine
Repotting	Spring, every 2 to 4 years. Wear gloves or wrap with folded newspaper.

Winter care

Keep cool and nearly dry, often watering once a month or less. Many need a cool, dry winter rest to bloom.

Pet safety

Not on the ASPCA list, use caution. Most desert cacti are not on the ASPCA list. Spines can injure pets, and some species, such as pencil cactus (a euphorbia, not a true cactus), are toxic.

Pet safety comes from the ASPCA Toxic and Non-Toxic Plants list. The list is not exhaustive, and a plant marked non-toxic can still upset a pet stomach. If a pet eats a plant and you are worried, call your vet or the ASPCA Animal Poison Control Center at (888) 426-4435 (a fee may apply). ASPCA Toxic and Non-Toxic Plants list.

Common problems

Soft, mushy base or black roots: Root rot from soil that stays wet too long. Common in winter.
Thin pale growth at the tip: Not enough light.
White cottony spots: Mealybugs. Wipe with rubbing alcohol on a cotton swab and isolate the plant.

How to check the soil

Finger test: push a finger into the soil up to the first knuckle, about an inch. Dry and crumbly means that layer is dry. Cool or damp means wait. For deeper checks use a wooden skewer: it comes out clean when the soil is dry.

All houseplants and the Light and Water tool