Why Are My Tomato Leaves Turning Yellow? 8 Causes and Fixes
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Yellow leaves are the most common complaint about tomato plants, and they have many possible causes. The good news is that the plant gives you clues. Where the yellowing starts, and what it looks like, usually points straight to the problem.
- A few yellow leaves at the very bottom of a large, healthy plant: normal aging. Snip them off.
- Lower leaves yellow with brown spots: a leaf disease. Remove them and improve airflow.
- Whole plant pale: hungry. Feed it.
- Yellow and wilting in wet soil: overwatered. Let it dry out.
First, check three things
- The soil. Push a finger 2 inches down. Is it soggy, nicely moist, or dust dry?
- Which leaves. Old ones at the bottom, new ones at the top, or all of them?
- The pattern. Evenly yellow, yellow between green veins, or yellow with spots? Turn a leaf over and look underneath too.
1. Normal aging
What you see: one or two of the lowest, oldest leaves turn yellow on a plant that is otherwise green and growing well.
Why: as a tomato grows tall and bushy, its bottom leaves are shaded and the plant stops supporting them.
Fix: nothing to worry about. Snip them off to improve airflow.
2. Too much water
What you see: yellow, limp leaves, often starting low, on a plant in soil that stays wet. Growth is slow.
Why: waterlogged roots cannot take up air or nutrients. It is the most common cause in pots without drainage holes and in heavy clay.
Fix: let the top 2 inches dry before watering again. Check that pots drain freely. Then water deeply but less often. See how often to water a vegetable garden.
3. Too little water
What you see: wilting, then yellow leaves with dry, crisp edges. The soil is dry and may have shrunk from the edge of the pot.
Fix: water thoroughly, then mulch the surface to hold moisture. Tomatoes in containers often need watering daily in summer. Our guide to growing tomatoes in pots explains why pot size matters so much.
Takes the guessing out of watering. Push the probe in near the roots and read the dial.
4. Hunger (nitrogen shortage)
What you see: older, lower leaves turn evenly pale green and then yellow, and the whole plant looks washed out and grows slowly.
Why: the plant moves scarce nitrogen from old leaves to new ones. It is common in pots, where watering washes nutrients away.
Fix: feed with a balanced or tomato fertilizer, following the label. New growth should green up within a week or two. The yellow leaves will not recover.
Feeds through the season. Pot-grown tomatoes need it most.
5. Leaf diseases: early blight and Septoria leaf spot
What you see: lower leaves develop brown spots, then turn yellow and drop. The problem climbs the plant over several weeks.
- Early blight: larger brown spots with rings inside them, like a target, often with a yellow halo.
- Septoria leaf spot: many small round spots with dark edges and pale centers.
Why: both are fungi that live in soil and on old plant debris. Rain and watering splash them onto the lowest leaves. Warm, wet weather speeds them up.
Fix:
- Remove spotted leaves with clean pruners and put them in the trash. Wash your hands and tools afterward.
- Strip the leaves from the bottom 8 to 12 inches of the stem so nothing touches the soil.
- Mulch to stop soil splashing up. See the best mulch for a vegetable garden.
- Water at the base, in the morning.
- If it keeps spreading, a copper fungicide can protect healthy leaves. Follow the label.
- Next year, plant tomatoes in a different bed.
Protects healthy leaves from blight and leaf spot. It prevents spread but does not cure infected leaves.
6. Magnesium or iron shortage
What you see: yellowing between the veins, while the veins stay green.
- On older, lower leaves: probably magnesium. It is common midseason on plants carrying a lot of fruit, and in pots.
- On new leaves at the top: probably iron, usually because the soil pH is too high for the plant to absorb it.
Fix: for magnesium, dissolve 1 tablespoon of Epsom salts in a gallon of water and water the plant with it once. For iron, test the soil pH before adding anything. Do not use Epsom salts routinely: it helps only where magnesium is actually short.
7. Pests
What you see: leaves with fine pale speckling that turn yellow or bronze. Look underneath.
- Spider mites: tiny dots and fine webbing, worst in hot, dry weather.
- Aphids and whiteflies: clusters of small insects and sticky residue.
Fix: spray the undersides of the leaves with a firm jet of water every few days, then use insecticidal soap if needed. Details are in how to get rid of aphids naturally.
8. Wilt diseases
What you see: yellowing that starts on one side of the plant or one side of a leaf. The plant wilts in the heat of the day even when the soil is moist, and gets steadily worse. If you cut a lower stem, the inside is streaked brown.
Why: Fusarium and Verticillium wilts are soil fungi that block the plant’s water channels.
Fix: there is no cure. Remove the plant and put it in the trash. Do not grow tomatoes, peppers, potatoes or eggplant in that spot for several years, and choose varieties marked “V” and “F” on the label, which are resistant.
Other causes worth knowing
- Transplant shock. Newly planted seedlings often yellow for a week or two, especially if nights are cold. They recover as they settle in.
- Seedling leaves. The first pair of small, smooth leaves always yellows and drops. That is normal.
- Weedkiller drift. Twisted, curled new growth along with yellowing can follow lawn herbicide sprayed nearby.
Should you remove yellow leaves?
Yes. A yellow leaf will not turn green again, and removing it improves airflow. Use clean pruners, cut close to the stem, and never remove more than about a third of the plant’s leaves at once. Put diseased leaves in the trash, not the compost.
Small, sharp blades reach between stems. Wipe them with rubbing alcohol between plants.
Frequently asked questions
Can yellow tomato leaves turn green again?
No. Once a leaf has yellowed it will not recover, but new growth will be healthy once the cause is fixed.
Why are the bottom leaves of my tomato plant turning yellow?
If only one or two, it is normal aging. If they have brown spots, it is a leaf disease. If many leaves are evenly pale, the plant needs feeding.
Is it safe to eat tomatoes from a plant with yellow leaves?
Yes. The fruit is safe as long as it looks healthy itself.
Do tomato plants need Epsom salts?
Only if they are short of magnesium, which shows as yellowing between green veins on older leaves. Otherwise it does nothing useful.
