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Why do houseplants turn yellow? There are many reasons, including moisture stress, lack of adequate or excessive light, nutrient deficiency, and insect damage. I will take you through these and provide solutions to your problem.
In essence, yellow leaves mean different things depending on the plant affected and what other symptoms the plant is showing. Growing plants is an activity that requires lots of patience, so you have to eliminate these common reasons for yellowing leaves, then wait to see what happens so you know the next step to take. This is a process of elimination.
The list below is the many reasons for yellowing leaves:
- Moisture Stress
- Lack of Light
- Unwanted Insects
- Temperature
- Nutrient Deficiency
- Aging
Moisture Stress
Most people are unsure how to measure just how much water a plant needs. The most common type of stress a plant may face is moisture stress. Overwatering or under-watering are two types of moisture stress.
If your plant is under-watered, to prevent transpiration and conserve moisture, it will sacrifice some of its foliage (in this case, maybe its leaves). Before they drop, the leaves will typically turn yellow.
When the plant is under-watered, asides from simply having yellow leaves, the plant may also curl inward and droop or crisp. If this is the case, you will need to water the plant immediately and, as well as ensure to water it regularly.
On the other hand, if your soil is kept too wet or watered more than necessary, this can have the same effect on your plant as keeping the soil too dry – in essence, dehydration. If you keep this up with the soil for long periods, the plant may go through root rot, which will not allow it to take up water, dehydrating your plants and making them turn yellow.
It is important to check how much moisture your plant is getting regularly. To do this, press a finger into the plant’s soil (about an inch). Make sure to go beyond the soil’s surface, as it tends to dry out the fastest. Your plant is likely thirsty if the soil is parched an inch below the surface. If the soil feels damp an inch below the surface, your plant may be getting enough water.
Lack of Light
Your plant’s leaves turn yellow because they receive too little light from the sun. Plants that receive too little light often turn yellow on the lower leaves before those leaves drop. Yellow leaves can also be the result of too much light.
For example, the leaves of shade lovers such as tropical ferns, nerve plants, and Calathea will slowly fade to yellow if kept in a sunny spot. On the other hand, houseplants that require sunlight, such as succulents, croton, and Jade plant, may become yellow if grown in dim conditions.
Typically, a plant that is yellowing from a lack of light will be yellow on the side that backs the light source. This is what many plant owners do or fail to do – not finding enough light to cover the entire plant. For instance, the leaves near the window might get all the light and block the opposite side.
If this is the case, you should consider moving the plant permanently to a location that receives more sunlight or letting it soak up the sun near a window for a couple of hours, monitoring the plant, tracking its progress, and seeing how it develops.
If the window light is still insufficient in your home, you might need to set up a few artificial plant lights. Try to make sure they cover the plant as optimally as possible. Some plants are sensitive and might be difficult to adjust, so keep a laser eye on them.
Unwanted Insects
Pests or unwanted insects can also cause a plant to turn yellow, attacking the plant inside and outside. Major types of such insects include:
- Mites
- Aphids
- Mealybugs
- Thrips
- Scale
- Whiteflies
These insects are often identified by their effects on the plants rather than any physical identification, majorly because they are too small to see with the eye.
The insects primarily suck the sap of the plant, usually leaving cuts, wing remnants, patches on leaves throughout the plant, and other materials, and destroy the overall quality of the plant, resulting in yellowing. These insects may be doing more damage than simply making the leaves of the plants yellow.
If pests are present, you’ll likely notice other signs of an invasion upon close inspection. There may be tiny holes in your plant, indicating the presence of spider mites on them. There may also be soft white wax on your plant, showing that there are Mealybugs.
Such unwanted insects may be taken care of in several ways, such as:
- Yellow sticky traps
- Hosing
- Natural predators
- Companion Planting
- Organic Neem Oil
- Organic SB Plant Invigorator
- Vacuuming
- Insecticides
Yellow Sticky Traps
These trap pieces of yellow cards with a double sticky side. Insects such as Aphids, Mealybugs, whiteflies, Thrips, and fungus nats are all attracted to the color yellow. These stick to the card and die on the card. Simply place these cards throughout your plants for the best effect.
Hosing
An effective method of dealing with these insects on outdoor plants is to hose them off. This knocks them to the ground and is too wet to climb back onto the plant and die.
Natural Predators
Natural predators such as ladybirds (ladybugs), Rove Bettle, and even nematodes are perfect predators to introduce to your garden. These come on little viles or tubs and can be released in a high tunnel or greenhouse. They hunt down their prey suppressing the numbers of these pests.
Companion Planting
Companion planting can help reduce the number of these insects that can turn your plant’s leaves yellow. Planting marigolds, for instance, can help stave off root-knot nematodes. Each insect that causes you a problem in the garden has a companion plant they don’t like. I will cover this in more detail in a future post.
Organic Neem Oil
Neem Oil has two effects on the garden. It can work as a pesticide and a fungicide. It effectively kills most mildew, such as powdery mildew or white mold. It can also kill Aphids, Mealybugs and whiteflies, but this list is not exhaustive.
Neem oil is organic and comes from the pressings of the seed and leaves of the Neem plant. This plant is a tree, and it hails from India.
Organic SB Plant Invigorator
Like Neem Oil, SB Plant Invigorator has two tasks in the garden. It is environmentally safe and works as a pesticide and a foliar feed. The product is designed as a supplement to help bring plants back from the brink and return to their vigor.
It is a soap-based solution; this was created to stick to the leaves to give the active ingredients time to do their work by providing the plant with the required nutrients. However, It has a side effect: it is very effective at killing Aphids, Whiteflies, Red Spider mites, and mealybugs.
Like Neem Oil, it is very good at dealing mildew and fungus. I use neem oil and SB Plant Invigorator to treat powdery mildew when growing Giant Zucchinis. I also made a detailed post about that if it interests you.
I have suffered from many of these insects with my plants over the years. I have found some very effective ways of treating them, and I made a video showing you the five best solutions to these problems. You can view that below.
Temperature
Plants need to be kept under certain conditions to develop properly. If they are kept too close to a heat vent, fireplace, air conditioner, or drafty window or door, they may react to extreme conditions for them by their leaves turning yellow. Most houseplants thrive in temperatures between 65 and 80 degrees F.
Nutrient Deficiency
Plant leaves may also turn yellow if they do not receive all the nutrients required.
In this case, the plant’s top leaves may be the first to turn yellow. In other instances, you might notice an unusual pattern of yellowing – the veins may remain dark while the tissue between them turns yellow.
Major reasons for nutrient deficiency are under-fertilizing and over-fertilizing. People often use too much fertilizer to make their plants grow faster, but this may be counterproductive because it creates an unsuitable environment that causes the leaves to burn out, turning them yellow.
Under-fertilizing means the plant will not receive an adequate amount of nutrients it is intended to receive, causing the plant not to have enough resources to go through a stable natural process, thereby causing the leaves to turn yellow.
Aging
As plants grow and age, it is not unusual to find that the lower leaves will turn yellow and drop off. This is simply a normal part of their growth. This doesn’t mean your plant is ill or any of the already mentioned reasons for plant yellowing is happening to the plant.
It just means that those lower leaves are shaded by higher foliage and are no longer needed by the plant. It’s best to allow that leaf to wither out to ensure it undergoes the completely natural process. However, ensure this is a leaf that has been there for a long time.
Conclusion
Indeed, seeing yellow leaves on your plants may not be a good sign. It may mean any of the following outlined but do not fret. Most of them require quick fixes and are largely inexpensive to sort. Make sure to monitor how the plant reacts to whatever solution you utilize and see how effective it may be to know whether you might need to adopt another resolution.
