ZZ plants are the easiest plants to grow indoors. These plants will thrive if you provide them with an ideal growing environment. The glossy green leaves capture attention quickly, creating a focal point in the house. And, to top it all off, they are extremely easy to maintain.
But what if one day you see black spots on your plant stems? They are not only unattractive but also harm your plant to a state where it is nearly impossible to save.
Additionally, yellow leaves and pests can accompany them, making the situation more critical. If you are confused about what caused these zz plant black spots on stems and their solutions, I am here to help you.
Before hopping onto the solutions, let’s get into the black spots on zz plant.
What are the black spots on zz plant stems?
The black spots are galls on the zz plants. The same fungus causes powdery mildew at the opposite end of its life cycle. When the fungus infects the zz plant stem, galls build, but they are not harmful to your plants. Even if your zz plant has them, they can be unsightly.
Galls vary in size and can be both small and large. You can find them on the plant’s stem’s upper side. They are usually white or yellow. Some of them may resemble a ball, while others may resemble a cup.
Various reasons can cause black spots on the stems of the zz plant, and now I will walk you through them.
What causes zz plant black spots on stems?
As you are aware, black spots on your ZZ plant can appear for a variety of reasons. The most likely cause is a fungus attack.
Though zz plants are hardy, they are prone to such problems. You shouldn’t be surprised to find these spots on your plant.
So, let’s take a quick look at what might be causing black spots on zz plant.
1) Too much sunlight
Have you kept your zz plant near a window or in direct sunlight? If this is the case, it may develop black spots.
In case you didn’t know, the ZZ plant dislikes direct sunlight. Despite being a desert plant, it is sensitive to excessive light. It may sound out of the box to you, but it is the truth.
As a result, exposing your zz plant to bright direct light will develop black spots and yellow leaves on the stem. The zz plant will die within a few weeks if you do not handle this problem immediately.
2) The pot is too big
In case you bought a too big plant for your zz plant, it may receive too much water. It will easily get black spots on zz plant. A large pot will hold a lot of potting soil, which can become wet and cold, causing the ZZ plant to absorb too much water.
3) Wrong Soil
One of the major reasons for overwatering ZZ plants is using the wrong potting soil. It may not drain freely if you use poor-quality potting or garden soil to potting up your ZZ plant. Too much water in the soil can rot the rhizome and cause black spots on zz plant stems.
4) Black Fungus
If your zz plant sits in wet and soggy soil for a long time, it can become a breeding ground for this fungus.
When the fungus begins to grow on the topsoil, it quickly spreads to the stem. When it attacks the stem, it weakens it and leaves black spots or patches on the surface.
It spreads like wildfire and makes survival difficult for the zz plant in the end. As a result, you should look after this problem as soon as possible before it damages other critical parts of the plant.
5) There is too much water
If you water too frequently, you are possibly overwatering your ZZ plant. It can cause black spots on zz plant stems.
Although the plant appears tropical, it can survive for a long time without water. You can water your plant every four weeks, and it will be sufficient to keep the plant happy. Anything more than this will cause the rhizome and roots to rot and the stems to turn black.
6) No drainage hole
If you overlook the importance of a drainage hole due to the aesthetic factor, it may cost you the life of your green zz plant. Letting your green buddy sit in the water for an extended period can cause zz plant black spots on stems.
When the excess water is not allowed to drain, the potting soil becomes saturated, and the plant absorbs too much water. It will damage your zz plant in the long run.
7) Stem rot
If your ZZ plant’s black spots are right at the base of the stem where it meets the potting mix, it could be a sign of stem rot. They can be slimy or mushy. Fungi is the one to blame, and poor watering practices pamper them.
Stem rot occurs when a plant’s stem is constantly wet from waterlogged soil or over-the-top watering.
Several types of moisture-loving fungi move in and take advantage of the damp conditions, eating away at the stem of your plant. Fungi’s spores can be found in the air, water, or potting mix.
ZZ plants do not require as much water as other tropical indoor plants. They do, however, demand some! After overwatering, under or no watering is the easiest way to harm a ZZ plant.
Your zz plant might be suffering from dehydration if you notice dry brown or black spots on zz plant stems and leaves, especially near the tips and edges.
You can also witness other signs of dehydration, including drooping, wilting, and curling leaves. Before you dip your ZZ plant in water, make sure to check how much moisture is already present in the potting mix.
9) Fertilization Issues
We all know fertilization boosts the plant’s growth. So, how can it be the cause for zz plant black spots on stems? Either both under or overdoing can result in problems.
ZZ plants do not require much fertilizer and can often survive without it. However, if you want your ZZ plant to look its best, you should feed it.
Overfeeding your zz plant will result in floppy, yellowing leaves with brown tips and splotches on your plant. Excess nutrients can scorch your plants’ roots, preventing them from functioning properly. On the other hand, underfeeding can result in a lack of nutrition.
10) Sooty Mold
It refers to fungi from the Ascomycete, Capnodium, or Saprophytic families that feed on zz plant pest secretions (honeydew) such as aphids and scale.
Fungal spores in the air land on the honeydew and produce a filthy, grimy substance. Although sooty mold alone will not harm your plant, it is unsightly, and the insect infestation causing it could be dangerous. You may have sooty mold if you notice any dark and powdery substance.
ZZ plants are well-known for their disease resistance. They are not susceptible to any diseases when they are healthy.
If your ZZ plant is not in good health or is living in an unsuitable environment, it may become a hub for a variety of fungal and bacterial diseases. It can easily cause zz plant black spots on stems and much more.
If you notice your zz plant’s leaves gradually develop black or brown spots, it could be suffering from one or more diseases.
These may include Fusarium, Pythium, Rhizoctonia, and Phytophthora fungal infections. These typically manifest as root or stem rot or fungal leaf spot, which causes zz plant black spots on leaves.
Black or brown spots on the zz plant’s leaves could also tell a tale of bacterial leaf disease. If you’ve tried fungicides that haven’t worked, bacteria is the one to treat.
12) Insects on ZZ plants
Although zz plants are not prone to insect infestation, it is possible, as with all indoor plants. If you’ve noticed sooty mold, honeydew, or even insects crawling on your ZZ plant, it’s high time to act!
Aphids are a common pest that, when in large numbers, can cause zz plant black spots on stems. They pierce the skin of zz plants with their sharp mouthparts and inject a liquefying enzyme before sucking the plant’s sap. I know they are too creepy, but these soft-bodied suckers are easy to deal with!
Scales are irritating because, by the time you notice them, they’re often firmly attached to the plant and challenging to get rid of.
Young scale insects can walk and spend their time looking for the perfect place to attach to your zz plant, which is usually the stem or under the leaves. After a while, they transform into limpet-like creatures that do not move and stick. They feed on your zz plant’s nutrients.
If you notice any tiny black or brown dots on the stem or under the leaves of your ZZ plant, scales may be the issue. Small numbers are not a big issue, but they spread quickly and can cause various problems if not controlled.
13) Low Humidity
If you notice any leaves curling up or dry black or brown spots that appear quickly. It may indicate that the humidity level in your house is too low for the plant to survive.
ZZ Plants lose water naturally through evaporation from their leaves, but when the air is too dry, they lose more than they can handle. It causes the leaves to dry and eventually fall off.
These plants belong to tropical areas and require at least 40% humidity to thrive.
Now that you all are well aware of the possible causes of black spots on zz plant, let’s move further. I will guide you on how you can revive your zz plant leaves turning black.
What are the solutions for black spots on zz plant stems?
Initially, you should find out the reason behind zz plant black spots on stems. After you know the cause, work according to the problem. Here, I am laying down all the possible methods to make your leaves green and healthy again.
1) Keep the zz plant alone.
You can easily solve a mild black stem problem by leaving the plant alone for a few days. Leave it on a shelf, bookcase, or in a corner to dry and recover from excessive watering.
Make sure you do not dip your zz plant in a pot tray or self-watering pot. You should wait four weeks before watering again.
If the plant is only slightly overwatered, it will recover, and the stems will revert to their normal green color.
2) Replant the ZZ plant in new soil.
If your plant is suffering from overwatering, you should repot your zz plant. It will help to get rid of zz plant leaves turning black.
Remove your plant from the pot and dump the soil. To repot the plant, use a clean pot with drainage holes and fresh soil.
3) Repair or replace damaged stems.
If you encounter any black spots on zz plants, you can clip them off. It will help in reviving your ZZ plant faster. Start by removing broken, brown, and bending stems. It is best to cut these 12 inches above the soil level.
4) Place it in a shadier location
If you’ve found out that bright direct light caused the zz plant black spots on the stem, it’s time to switch places. You can get rid of the markings on your ZZ plant’s stem by moving it to a less bright environment.
The existing marks are unlikely to disappear, but your plant will be less likely to develop new ones. ZZ plants do better in low-light environments than many other plants, but they still require some light to thrive.
You can keep your ZZ plant in a location that receives at least 12 hours of indirect light per day. Place them several feet away from the window in a bright room.
5) Water the plant thoroughly – but only once.
As you already know, overwatering can cause a blunder to your zz plants. So, to revive your green leaves, make sure to water less.
Before watering your zz plant again, let the soil dry an inch. You should permit the excess water to drain before placing it on its pot tray.
6) Keep your soil dry
Let the soil dry if you want to get rid of zz plant dark spots on stems. If growing in a pot, you should water only as needed to keep the roots from drying out.
Fungus grows in wet soil, so keep your potted plant dry but moist. You should fertilize a bit only when the soil is wet, as dry soil may burn the roots.
7) Stem rot solution
To combat stem rot, you should repot your zz plant. Repot your plant into a well-draining potting mix, and make sure not to damage the stem.
Tip: You should also check for root rot at the same time, as the two conditions frequently coexist.
Using clean scissors, cut away any damaged roots.
Place your zz plant in a warm, dry location with indirect light. You should use proper watering techniques and avoid the potting mix becoming waterlogged. Stem rot is a severe problem; unfortunately, it may be too late to save your plant once you notice it.
8) Fertilize Properly
As you know already, feeding your plant boosts healthy growth, so fertilize in an adequate amount. Once a month during the zz plant’s growing season (spring and summer) is sufficient to keep the foliage lush and healthy.
Make sure not to feed your plant in autumn until it begins to grow again in spring. Do not go over the package directions.
9) Increase Humidity
If your home lacks humidity according to the zz plants, you can use a humidifier. It will raise the humidity. ZZ plants prefer at least 40% to 50% humidity in the environment.
To resolve the zz plant black spots on stems, you can also use humidity trays. Fill the tray with water and place pebbles inside it. It should be large enough to keep your pots out of the water. Placing your pots on top will provide your plants with a private humidifier.
Alternatively, you can bring more green friends to create a family. Adding plants will increase the humidity level in your space! The water they lose through their leaves contributes to the atmosphere’s moisture.
10) Combat Diseases
The bacterial disease has no treatment, so the best thing to do for your zz plant is to remove any affected leaves and re-pot them. If the infection is severe, you should probably buy a new plant.
Although many different types of fungus can cause diseases, the treatment is the same for all of them. To treat the infection, follow the mentioned steps to make your ZZ plant less inviting to the spores of these fungi:
- You should increase the flow of air around your plant.
- Make sure to maintain a humid environment for zz plants (ideally 40-50%)
- Do not mist the plant’s leaves.
- Don’t let the potting mix become soggy.
11) Remove insects
To revive your zz plant’s leaves, spray a solution of horticultural soap or Castile liquid soap and water on your plant. You can easily get rid of aphids. Use 2 – 2 1/2 teaspoons of Castile soap per gallon of water.
Spray your zz plant every few days until the aphids are gone, then re-spray if they return. You can also use rubbing alcohol; simply rub them off the plant.
These creatures are tough to identify. If you come across these tiny, brownish, semi-transparent, slowly moving dots, spray the same soap mixture I mentioned for aphids.
Although the soap spray will be ineffective for adult scales. Using a medium-soft bristled brush, remove the adult scale from your zz plant. You should remove all the infected leaves to stop the attack.
Fixing the black spots on ZZ plant stems can be a challenging task for gardeners, but the hard work is all worth it. First, you must determine why my zz plant has black stems. Then you must choose how you can handle the situation from the steps I mentioned above.
You should water your zz plants every four weeks, allowing the plant to drain well in a sink or outside, and then place it on a dry pot tray.
Usually, you can easily recover your zz plant black spots on stems by reducing the water. If the soil on your ZZ plant is very wet and damaged, repot it in a smaller pot.
Let me know how you removed black spots on zz plant stems. I would love to hear them.