Why Are My Plant’s Leaves Turning Yellow?

If only the oldest leaves at the bottom of the plant turn yellow and drop, slowly, while new growth looks healthy, this is often just natural ageing. Plants shed old leaves to redirect energy to new growth.

If it is happening to several lower leaves at once, it can point to a nitrogen shortage — the plant is moving nitrogen from old leaves to feed new ones. A balanced feed during the growing season usually fixes it.

Overwatering is the most common cause of yellow leaves on houseplants. Roots sitting in waterlogged soil cannot get oxygen and begin to rot. Leaves go limp and yellow, sometimes with brown, mushy patches, and the soil smells sour.

Let the soil dry out, check the pot has drainage holes, and empty any water sitting in the saucer. If the roots are brown and mushy, trim the rotten parts and repot in fresh, free-draining mix.

Underwatered plants also yellow, but the leaves tend to dry out and go crisp from the edges first. The soil pulls away from the side of the pot. Water thoroughly until it runs out of the drainage holes, and if the soil has become hard to wet, soak the whole pot in a bucket for half an hour.

When the leaf tissue turns yellow but the veins stay green, it is called chlorosis. On new leaves it often signals an iron or manganese deficiency, frequently caused by alkaline soil or water that locks those nutrients up. On older leaves it can indicate a magnesium shortage. A feed containing trace elements, or an acid-loving plant food for plants such as blueberries and azaleas, can help.

Fine yellow speckles, sometimes with webbing, suggest spider mites; sticky leaves suggest aphids or scale. Check the undersides of leaves with a magnifying glass. Wiping leaves, rinsing the plant, or using insecticidal soap according to the label usually brings these pests under control.