Why Are My Tomato Leaves Turning Yellow? Read the Pattern, Then Fix It
A yellow tomato leaf is a symptom, not a diagnosis. Where it starts on the plant narrows the cause quickly and tells you whether to feed, prune, wait or pull the plant.
Start by noting where the yellow begins. Yellowing on the lowest leaves usually means natural aging, a nitrogen shortage or a leaf-spot disease climbing the plant. Yellowing on the newest growth points to a different group of problems, such as poor iron uptake, herbicide injury or a virus. Match the pattern below, deal with the cause, and judge your progress by the new leaves, because badly yellowed ones rarely recover.
Quick diagnosis table
| Where it starts | What you see | Likely cause | What to do |
|---|---|---|---|
| Lowest leaves, no spots | A few shaded leaves fade; the rest of the plant looks healthy | Normal aging | Nothing, or snip them off |
| Lower leaves, whole plant pale | Even yellowing on older leaves, slow growth | Nitrogen shortage | Feed lightly; do not overdo it |
| Lower leaves, green veins | Yellow between the veins, older leaves first | Possible magnesium shortage | Soil test before adding anything |
| Lower leaves with spots | Spots first, then yellowing and leaf drop | Early blight or septoria leaf spot | Remove affected leaves, mulch, water at the base |
| One side of the plant | Yellow leaves on one side, wilting in the heat of the day | Fusarium or verticillium wilt | Slit the stem to check; no cure |
| Newest leaves, green veins | Young leaves yellow while veins stay green | Poor iron uptake, often linked to soil pH | Test soil pH |
| Newest leaves, cupped and small | Yellow edges, stunted bushy plant | Tomato yellow leaf curl virus | Remove and bag the plant |
| Newest leaves, twisted | Distorted growth, twisted stems | Herbicide drift | No remedy; watch new growth |
Yellowing that starts on the lower leaves
Normal aging
The oldest leaves sit in the shade of everything above them. A few fading at the bottom of a vigorous plant, with no spots and good new growth, is not a problem.
Nitrogen shortage
Nitrogen moves within the plant, so older leaves give it up first and turn evenly pale. The University of Wisconsin notes it is most common in containers, where frequent watering and low fertility go together. Adding nitrogen fertilizer helps, but too much pushes leaves at the expense of flowers and fruit. Follow the rate on the label and stop there.
Magnesium or other shortages
Yellow between the veins of older leaves can mean a magnesium shortage, though other nutrients can produce similar patterns. Our nutrient deficiency chart compares them side by side. Skip the reflex dose of Epsom salt: Oregon State University Extension says to use it only if a soil test shows low magnesium, and the University of Minnesota warns that too much magnesium can make blossom end rot worse.
Early blight and septoria leaf spot
Both begin low on the plant and move upward. Look closely: early blight makes larger spots with target-like rings, while septoria makes many tiny spots with pale centers and dark borders. Leaves then yellow and drop. Our guide to early blight, late blight and septoria shows how to separate them and what to do for each.
Yellowing on one side of the plant
Fusarium wilt tends to appear around mid-season, after flowering. The oldest leaves turn yellow and droop, often on just one side of the stem, and the plant may wilt only in the hottest part of the day before the problem climbs upward. Verticillium wilt looks similar but is more common in cool weather.
To check, cut a lower stem lengthwise. Brown or tan streaks in the water-conducting tissue just under the surface point to a wilt disease. Clemson’s tomato disease guide lists no chemical control for fusarium wilt, and University of Wisconsin Extension calls chemical control impractical for both wilts. Remove affected plants, keep them out of the compost pile, and next year choose varieties labeled VF (resistant to verticillium and fusarium). Wisconsin suggests moving susceptible crops away from that spot for five to seven years, which is hard in a small garden, so resistant varieties are usually the practical answer.
One look-alike: tomatoes growing near black walnut or butternut trees can show the same outward symptoms, caused by toxins from the trees. Those plants have no internal streaking.
Yellowing on new growth
- Iron. Young leaves turn yellow with green veins, which often reflects soil pH rather than a true lack of iron. Iowa State University points out that many nutrient problems come from incorrect pH.
- Tomato yellow leaf curl virus. Spread by whiteflies, mainly a threat in the southern US. New leaves cup, edges yellow, and the plant stays small and may drop its flowers. There is no treatment. Remove and bag the plant.
- Herbicide. Drift from lawn weed killers such as 2,4-D or dicamba distorts stems and foliage. Glyphosate can cause white or yellow patches at the base of leaflets. No fix exists, but plants that survive may put out normal growth later.
Rule out water stress
Soggy soil and dry soil can both leave a plant pale and unhappy, because stressed roots take up less. Push a finger into the soil a few inches down before you do anything else. If it is sopping or bone dry, correct that first and see how often to water vegetables. Young transplants in cool soil often sit pale for a while too, since cool soil slows early growth.
What to do, in order
- Note where the yellow started and whether it is on one side, on the veins or around spots.
- Check the undersides of leaves for pests and the stem base for damage.
- Check soil moisture a few inches down.
- Remove spotted leaves on a dry day and put them in the trash, not the compost.
- Mulch and water at the base so soil does not splash onto leaves.
- Get a soil test before fertilizing an in-ground plant. Our guide on reading a soil test explains the results.
- If the pattern fits none of the above, ask your county extension office. Many offer plant diagnostics, and a clear photo or sample helps.
Bottom line
Bottom leaves with no spots are usually fine. Evenly pale older leaves suggest nitrogen, spots suggest a leaf disease, one-sided yellowing suggests a wilt, and strange new growth suggests a virus or herbicide. Test before you fertilize, and never treat a spray as the first step.
FAQ
Should I cut off yellow tomato leaves?
Yes, if they have spots or are dying. Remove them on a dry day so you do not spread disease. Do not strip many healthy leaves at once, since leaves shade fruit and feed the plant.
Will Epsom salt fix yellow tomato leaves?
Only if a soil test shows low magnesium. In most gardens it does nothing useful and too much can cause other problems.
Why did my new transplants turn yellow?
Cool soil and transplant stress are the usual suspects. Colorado State University notes that a water-soluble fertilizer can help renew growth once warm weather returns.
Will a yellow leaf turn green again?
Sometimes a pale leaf greens up slightly after feeding, but a fully yellow one usually will not. Look for healthy color on new growth instead.
