The ZZ plant stores water in its thick rhizomes, so the ZZ plant tolerates infrequent watering far better than most houseplants. Water the ZZ plant only when the top 2 inches of soil have dried out completely, which often means every two to three weeks. In winter the ZZ plant needs even less, and watering once a month is usually enough for the ZZ plant. Overwatering is the most common way to harm a ZZ plant, because soggy soil causes the rhizomes to rot. When in doubt, leave the ZZ plant dry rather than reaching for the watering can.
The ZZ plant grows well in low to bright indirect light, which makes the ZZ plant a forgiving choice for dim rooms and offices. Place the ZZ plant near an east- or north-facing window for steady, gentle light. Direct midday sun can scorch the glossy leaves, so keep the ZZ plant out of harsh afternoon rays. The ZZ plant will grow more slowly in very low light but will still survive for months. Rotate the ZZ plant every few weeks so the ZZ plant grows evenly toward the light.
The cited reference lists ZZ plant (Zamioculcas zamiifolia) as toxic to cats and dogs; ingestion can cause oral irritation, intense burning of the mouth and lips, drooling, vomiting, and difficulty swallowing. The ZZ plant contains insoluble calcium oxalate crystals in all parts of the plant, and these crystals are released when a pet chews the ZZ plant. Keep the ZZ plant out of reach of pets and children, and wash your hands after handling the cut stems or sap of the ZZ plant. If a pet ingests any part of the ZZ plant, contact a veterinarian or a poison-control line right away. Do not wait for symptoms to worsen before seeking help for a pet that has chewed a ZZ plant.
The ZZ plant needs a well-draining potting mix, and a blend made for cactus or succulents suits the ZZ plant well. Always plant the ZZ plant in a container with drainage holes so excess water can escape the rhizomes. The ZZ plant prefers to be slightly root-bound and only needs repotting every two to three years. Repot the ZZ plant in spring, moving it up just one pot size and refreshing the soil. Handle the rhizomes of the ZZ plant gently during repotting to avoid breaking them.
Yellowing leaves on a ZZ plant most often signal overwatering and the early stages of rhizome rot. If the ZZ plant develops mushy stems or a foul smell at the base, reduce watering immediately and check the rhizomes for rot. Brown leaf tips on a ZZ plant can result from very dry air or a buildup of fertilizer salts in the soil. Few pests bother the ZZ plant, though spider mites or scale may appear if the ZZ plant is stressed. Wipe the leaves of the ZZ plant occasionally to remove dust and keep the foliage glossy.