Why Your Houseplant's Leaves Are Turning Yellow

Read the Pattern Before You Change Anything

Houseplant leaves turn yellow most often because the plant is overwatered. University of Maryland Extension calls overwatering the number one reason indoor plants fail. The other common causes are soil left dry for too long, too little light, a nutrient shortage, sap-sucking pests and ordinary aging. To tell them apart, check the soil 1 to 2 inches below the surface and note which leaves are affected.

Yellowing has its own name, chlorosis, and it is often one of the first signs of stress. University of Maryland Extension notes that symptoms blamed on insects or diseases often come from the plant’s environment. The table below pairs each pattern with its usual cause.

What you see	Likely cause	First step
Yellowing across the plant, soil wet	Overwatering	Stop watering until the soil dries 1 to 2 inches down
Lower leaves yellow, soil repeatedly very dry	Underwatering	Water thoroughly and check more often
Lower leaves yellow, plant pot-bound	Nitrogen or iron deficiency	Repot or fertilize lightly
Yellow between green veins	Manganese, iron or magnesium deficiency	Fertilize with a product that lists micronutrients
Yellow leaves with tiny speckles, webbing	Spider mites	Inspect leaf undersides and treat the pest
Foliage fading to yellow-green in winter	Low light	Move closer to a window or add a light
One old leaf at the base	Natural aging	Remove the leaf

Overwatering and Root Rot

Clemson’s fact sheet lists several causes for a plant that yellows all over, then adds that the symptom is most often caused by overwatering. The mechanism is a lack of air. Too much water decreases the oxygen available to roots and favors root diseases, and roots that die cannot supply the leaves.

The check takes ten seconds. Push a finger into the pot and feel the soil 1 to 2 inches down. University of Georgia Extension advises watering only when it is dry at that depth, and warns that the surface may be dry while the root zone is saturated. Watering by the look of the top layer is how many plants get drowned.

If the soil has stayed wet for a long time, slide the plant out of its pot. Clemson describes rotted roots as brown to black and sometimes soft. When only a few roots are affected, cut them out and repot in fresh, sterile potting soil. Then make sure the container drains, and water less often. The full sequence is in the guide to saving an overwatered houseplant.

Too Dry for Too Long

Underwatering produces yellow leaves too, but in a different place. Clemson notes that lower foliage may turn yellow and die back when a plant is allowed to become too dry for an extended time. Chronic under-watering also brings wilting and leaf curling.

Clemson adds that plants in pots that are too small will drop leaves. If you water thoroughly and the soil dries out again very quickly, check the signs that a houseplant needs repotting.

Low Light, Especially in Winter

Too little light is on every extension list of causes. University of Georgia Extension points to the season: indoor light is often low or limiting in December and January, and foliage may fade or turn yellow-green in response. A plant that did well on a shelf in July can be short of light in the same spot in midwinter.

Move it closer to a window for those months, or add a fixture. The guide to grow lights for container gardens explains how much light different plants need. The opposite problem exists as well, since University of Maryland Extension includes extremely sunny conditions among the causes of leaf injury. Change a plant’s position in steps instead of moving it from a dim corner to a hot sill.

Temperature Swings and Drafts

UC IPM lists exposure to low temperatures among the causes of yellowing and dropping leaves. It also ties a yellow-green cast across the whole plant to high temperatures, especially when combined with dryness. University of Georgia Extension adds sudden changes in temperature and cold or hot drafts to the stresses that make houseplants wilt.

Look at what is near the pot: an exterior door, a single-pane window in January, a heating vent, an air conditioner. If the yellowing began when the heating or cooling season started, move the plant away from the air stream and watch the new growth.

Nutrient Shortages

A plant that has not been fed or repotted in a long time can run short of nutrients. The pattern points to which one.

Yellowing that starts on the older, lower leaves suggests nitrogen. UC IPM describes yellow-green older leaves as a sign of insufficient fertilizer, especially nitrogen, and Clemson links yellow lower leaves to nitrogen or iron deficiency in pot-bound plants.

Yellowing between the veins while the veins stay green is called interveinal chlorosis. The Royal Horticultural Society, writing about plants in general, says it usually indicates manganese, iron or magnesium deficiency. Iron deficiency shows on the youngest leaves first, while manganese and magnesium symptoms tend to begin on older leaves.

Fertilize at the label rate and no more. Clemson warns that fertilizer and minerals from hard water accumulate in the soil and damage roots. Where that has happened, the fix is to repot in fresh soil.

Pests That Cause Yellow Leaves

Sap-sucking insects and mites drain leaves and leave them yellow. Turn a few leaves over before settling on another cause.

• Spider mites: yellowed leaves with tiny speckling that later turn bronze and dry. Webbing may show near the growing points.
• Mealybugs: stunted growth, yellowing and leaf wilting.
• Whiteflies: leaves that yellow and drop.

These symptoms are UC IPM’s. For the first of them, see how to get rid of spider mites on houseplants.

When a Yellow Leaf Is Normal

An occasional leaf drops from natural aging, as University of Georgia Extension notes. If a single old leaf at the base yellows while the plant keeps producing healthy new growth, remove it and carry on.

Several leaves yellowing at once is different. If the stress is not relieved, yellow leaves may turn brown, so work through the table from the top and correct one thing at a time. Changing water, light and fertilizer in the same week makes it impossible to tell which change helped.