Are Your Indoor Plant Leaves Turning Yellow? Here's Why—and How to Fix It

One of the most common problems you'll encounter when caring for indoor plants is the leaves turning yellow. While this issue can be caused by something as simple as old age, it can also be a sign of more serious problems lurking beneath the soil, like root damage. Because so many factors can cause this issue, identifying the reason your houseplant's leaves are fading can be difficult. To help, we're sharing a few of the most common reasons indoor plant leaves turn yellow.

Over or Underwatering

Plants need water to survive, but too much or too little water can be a bad thing.

Too Much Water

Too much water around the roots causes an anaerobic environment where bacteria can build up, says Linda Langelo, horticulture specialist at Colorado State University. "The roots cannot absorb any nutrients. This causes yellowing of lower and inner leaves. The yellow sections will get mushy, and then the leaves drop," she says.

Too Little Water

Too little water can also cause your plant's leaves to turn yellow. "Leaves yellow when the potting mix is too dry for a similar reason as when the potting mix is too wet, but in this case, there’s not enough moisture in the potting mix for the roots to pull up into the plant," says Justin Hancock horticulturist for Costa Farms. "Plants that are too dry are more often going to be associated with the plant wilting (but overwatering can also cause wilt in some species)."

To gauge if you're over or underwatering, put a fingertip in the soil or pick the pot up to get a sense of its weight—the wetter a plant is, the heavier it will be; the drier it is, the lighter it will be.

Poor Soil Drainage

Poor drainage in a houseplant occurs when water accumulates in the pot and drowns the roots. If you think your houseplant is yellowing due to poor soil drainage, check the container to make sure it has drainage holes. Also, don't put gravel at the bottom of any houseplant container. "The water moves more quickly through the porous soil mix than it will move through the gravel," says Langelo.

If your container already has drainage holes, you may want to repot your houseplant in a container with soil that drains better.

Inadequate Sunlight

Giving your plants too much or too little sunlight cause cause the leaves to yellow.

Too Much Sun

Too much sun can burn leaves, giving them a bleached appearance. This can happen if your plant is given too much sunlight too fast. "Slowly moving your plant closer and closer to a window over the course of a couple of weeks can help it build up tolerance to the sun so it can thrive right in the windowsill," says Hancock.

Too Little Sun

Too little sun can also damage the leaves of your houseplants. When this is the case, the yellowing typically begins on the lower leaves before they drop. "The leaves that are yellow first are farthest from the source of light," says Langelo.

There are three ways to fix this: rotate the pot once a week, find a better source of light, or use LED plant lights.

Root Damage

Many things can cause root damage, including inadequate watering, fluctuations in temperature, or too much fertilizer. Root damage can lead to yellowing, small pale-colored leaves, or leaves with brown splotches. To fix root damage, remove the plant from its container, brush away as much of the soil as possible, prune away any mushy roots, then repot the plant. "If there are too many mushy, soft roots, the houseplant might not survive when you repot it into a new container with well-drained potting soil," says Langelo.

Improper Soil pH

If a houseplant’s soil pH is too low or too high, it cannot access certain nutrients that are available in the soil and cause yellow leaves. Most houseplants like neutral soil or a slightly acidic pH of 6.0 to 7.0, says Langelo. If the soil is too acidic then leaves show a dark dull green color. If the soil is too basic, it can result in iron chlorosis, which is an iron deficiency that manifests as yellowing leaves with veins that remain green, says Langelo. The best way to fix this issue is by repotting your houseplant.

Fungal Infection

Fungal infections can also cause yellow leaves, which typically start with blotches or spots that can spread. Prevention is the best way to prevent a fungal infection. "Space plants far enough apart to give each one good air circulation and reduce moisture," says Langelo. Watering early in the morning at the bottom of the pot and reducing humidity can also help prevent fungal infections.

Age

Each individual leaf on your houseplant has an individual lifespan. "When that leaf gets old, the plant will shed it," says Hancock. "This often starts by yellowing before the leaf falls. With most species this happens slowly, leaf by leaf. But some plants can drop more leaves at one time seasonally, just before they push out new growth."

Temperature Fluctuations

Houseplants grow best at day temperatures between 70 to 80 degrees Fahrenheit and night temperatures between 60 to 68 degrees Fahrenheit. "Cold drafts can come from windows, doors, or air ducts and can turn leaves yellow," says Langelo. To fix this, learn what temperature range your houseplants like and see if it is best suited to your home’s environment.

Exposure to Chemicals

Be mindful of exposing your houseplants to chemicals indoors, which can cause their leaves to yellow. "Outdoors, we’re usually more aware of chemicals like pesticides being used, but indoors, everyday products can harm plant foliage when they come in contact with the leaves," says Hancock. "For example, if you have a plant on a table, spray furniture polish on the table, and there’s some overspray onto the plant, the chemicals in the polish may cause the affected plant leaves to yellow and drop." When cleaning or using harsh chemicals, make sure your plants are protected.

Pests

Yellow leaves can be caused by several pests and diseases, such as aphids, spider mites, mealybugs, and scales. "These invaders feed on plant tissues or disrupt their normal functioning, leading to discoloration and damage," says Langelo. Regularly check your plants for small insects, webbing, or unusual spots on the leaves. If an infestation is detected, immediately treat it. "Insecticidal soap can help control aphids, spider mites, and mealybugs. Horticultural oils can help control scale by smothering young crawlers," says Langelo.

Environmental Stress

Environmental factors such as shock after repotting, moving plants to a new location, extreme temperatures, drafts, sudden changes in humidity, or exposure to pollutants can cause yellowing leaves. "Minimizing environmental stress by providing stable conditions and gradually acclimating plants to new environments can help prevent leaf discoloration," says Langelo.