Brown stems on ZZ plants can be caused by overwatering, stem damage when the plant is moved, too much sun or rotting roots. Make sure the ZZ plant is growing in well-draining soil and is only watered every 4 weeks. Avoid leaving the base of the pot sitting in water and keep the plant out of direct sunlight.
This article will explore the top 6 causes off brown stems on ZZ plants and what you can do to solve each problem.
Top 6 causes of brown stems on ZZ plants and solutions
Here are the top 6 causes of brown stems on ZZ plants and what to do to solve each one.
1. Too much water
Excess watering is the top cause of brown stems on ZZ plants. ZZ plants grow from rhizomes that hold water so the plant can survive for long periods without it. When the plant is given too much water the rhizomes can rot and kill the plant.
The first symptoms of overwatering are often brown or black marks on the stems. The stems will be damaged by the excess water and if the problem continues and the roots will struggle to absorb nutrients. The stems will turn brown and eventually die off.
The easy solution is to reduce your watering schedule. Water the ZZ plant deeply every 4 weeks in your sink or outdoors. Let the water drain through completely before placing the plant back inside the pot or on a pot tray.
Avoid using self-watering pots or make sure that the base is always empty of water. The stems of the ZZ plant will turn brown quicky if they are left soaking in water.
2. Stem damage
Damage to stems when you move the plant or separate the stems for division can cause browning. The stems are delicate and any bending or impact can cause the stem to brown.
If the stem is damaged lower down and close to the base it can be trimmed off and grown into a new plant. Do this straight away and you can grow a new plant from the bent stem.
For more on how to fix bent and broken stems on ZZ plants check out my previous article: ZZ Plant broken stem repair guide | 3 Easy Steps
3. Too much light and sun
ZZ plants are light sensitive so if they are placed in a sunny spot or are getting reflected light from a window they can turn brown. Direct sun can burn the leaves or stem turning them yellow or brown.
Move the plant to an area away from a window. Make sure it is at least 3 feet away from a window and not in the path of direct sun. The top of a bookshelf or a floating wall shelf is a great place for a ZZ plant.
4. Rotting roots
Rotting roots on ZZ plants can cause the stems to turn brown. When the roots rot due to soggy soil or overwatering the stem will not receive the nutrients or water flow it needs and will start to die off and turn brown.
Repot ZZ plants in large pots where soil has become too soggy. If the plant is placed in a pot that is too big the soil will stay wet and cold and can rot the ZZ plant roots. Always allow the pot to drain well before putting it on a pot tray and only water every 4 weeks.
5. Not enough nutrients
A lack of nutrients can cause ZZ plant stems to turn brown. A lack of nutrients particularly iron or nitrogen can cause the stem to turn yellow and then brown.
Feed your ZZ plant in spring with slow release fertilizer with a range of nutrients. An indoor plant food is perfect because it will be low odor. Water the plant well after fertilizing to start to deliver the nutrients to the plant.
A dose of liquid fertilizer can also help and give the plant a rapid dose of nutrients. Add some dilute fertilizer to your plant when you water and you should see the color return to the stem.
6. Poor soil
Growing ZZ plants in poor soil can cause the stem to turn brown. Poor soil will not drain well and will lack the range of nutrients the plant needs.
The best potting soil to use when repotting ZZ plants is a premium all purpose soil. This will contain a range of organic matter, slow release fertilizer and sometimes even soil wetter which help to keep the soil consistently moist. Repot a suffering ZZ plant into fresh soil and it will start to recover within weeks.
Brown stems on ZZ plants | Summary
Brown stems on ZZ plants are usually caused by overwatering. The rhizomes of the ZZ plant can hold water for a long time so they only need to be watered every 4 weeks. Thoroughly wet the soil and always allow it to drain. Give the plant some slow release indoor plant food in spring and make sure it is not sitting in direct sunlight.
I am an accredited practicing dietitian, experienced gardener and a dedicated cook. I love writing and sharing my experience so you can learn from my successes and mistakes.