Yellow tomato leaves are the plant's way of saying something is short. Where the yellow appears tells you a lot: on the oldest leaves at the bottom, or on the newest leaves at the top.
Read the Leaves
| Where the yellow is | What it looks like | Likely cause |
|---|---|---|
| A few of the lowest leaves | Yellow, then brown, one or two at a time | Normal aging; remove them |
| Older, lower leaves | Even yellowing that moves up the plant | Nitrogen running low |
| Older, lower leaves | Yellow between the veins, veins stay green | Magnesium running low |
| Newest leaves at the top | Yellow between the veins, veins stay green | Iron lockout, usually from pH too high |
| All over, with wilting | Yellowing plus drooping | Root damage from root rot |
| All over, pale and stretched | Pale growth with long stems | Not enough light |
Nutrients like nitrogen and magnesium can move inside the plant, so when they run short, the plant takes them from old leaves to feed new ones, and the old leaves yellow first. Iron can't move, so shortages show on new leaves.
Check in This Order
- pH. Out of range, the plant can't absorb nutrients that are in the water. Keep it between 5.5 and 6.5. See Kratky tomato pH.
- Water level and roots. Are the water roots in the solution? Are the roots white or brown? See topping up a Kratky tomato reservoir.
- Nutrient strength. A big tomato can use up a weak solution. Check EC and top up at the right strength. See Kratky tomato nutrients.
- Light. Indoors, check hours and distance. See grow lights for indoor tomatoes.
Yellow leaves don't turn green again once damaged. Judge the fix by the new growth.
Back to Kratky tomato problems.
Frequently Asked Questions
Why are the bottom leaves of my tomato turning yellow?
A few yellowing bottom leaves are normal aging. If yellowing keeps moving up the plant, nitrogen or magnesium is likely running low.
Why are the top leaves of my Kratky tomato yellow?
Yellow between the veins on new leaves usually means iron lockout, most often because the pH is too high.
Should you remove yellow tomato leaves?
Yes, remove leaves that are mostly yellow or brown. They no longer feed the plant, and removing them improves air flow around the base.