There's no plant quite as tough as the ZZ Plant (Zamioculcas zamiifolia), but they can still get sick with symptoms of brown leaves.
Let's look into 9 reasons why your ZZ plant is turning brown and what you can do to save them.
1 Over-watering The ZZ is one of the most drought-tolerant of all the popular indoor plants. A waxy coat on their leaves and rhizomes underground keeps them well hydrated no matter how hot or dry their environment. Leave the soil to dry for a week or two, or transfer the plant to well-draining soil.
2 Poor Water Quality Many chemicals added to tap water to protect human health, like chlorine or fluoride, will build up in leaves over time and cause damage to the plant's tissue. Leave a jug or bowl of water overnight, and most chlorine will evaporate by morning.
3 Pest Infestation Damage from insect pests can vary, but spider mites leave blotchy brown patches where they dine. Mealybugs can cause the leaf to brown from the tip down. Give the ZZ a wipe-down with a bit of neem oil.
4 Too Much Direct Sunlight One of the reasons the ZZs make such great house plants is that they are very good at using low light. Too much light – especially direct sunlight – and they'll develop sunburn. Relocate your ZZ away from sunbeams and bright light.
5 Lack of Humidity Indoor environments have dry air with around 20% humidity or less, and ZZ plants prefer humidity levels between 40 and 50%. A pebble tray will create a gentle humidity in the surrounding air. You can also cut to the chase with an electric humidifier.
6 Disease The most common disease to watch for are fungal rust and bacterial leaf spots. You can apply a copper-based fungicide or move the plant to quarantine and let the ZZ shrug it off without further intervention.
7 Nutrient Deficiency Different nutrient deficiencies show signs of struggle, but lacking some nutrients under the right conditions can fuel brown leaves on a ZZ Plant. If you are worried about nutrient deficiency, consider replanting your ZZ in a new pot with fresh soil and fertilizer.
8 Temperature Stress Chilly plants can throw yellow leaves in protest that will eventually turn brown and drop off, while prolonged periods of heat can stress the ZZ in much the same way as underwatering. Aim to keep your ZZ between 65-90°F (18-32°C).
9 Transplant Shock If you have brown leaves in the weeks after a repotting, your brown leaves are likely from transplant shock. Be patient and just wait it out. ZZ plants can be slow growers.
Click on the link to learn 4 ways to keep a ZZ plant healthy. ⬇