Indoor tomato plant leaves are yellow and curling

by Maria Elkady
(Meadville, Pa)

Q. We purchased a tomato plant already potted in Florida and carefully brought it back to western PA in the beginning of December. At first the plant was doing well. It already had several blooms and a very small tomato. Since bringing it home the leaves have begun to curl and turn yellow. The house temp is between 75-80 degrees. We have it by a window and put a lamp on it for several hours a day. I repotted the plant and gave it Miracle Gro for Tomatoes. Now the small tomato has fallen off. Any suggestions?

A. Yellowed, curled leaves on an indoor tomato plant can have several causes. Here's a checklist for you to consider.

The need for sunlight. If affected leaves are primarily on the lower part of the plant, then that area may not be getting enough light. Without light, the lower part of the plant can't receive as many nutrients -- hence the yellowing.
Overwatering or underwatering. Either can cause yellowed leaves. Check your soil with your finger (unscientific, we know, but it works!) When adequately watered, soil should feel damp 3-4 inches deep. (Learn more about watering tomatoes adequately.)
Fertilizing too much or too little. Over fertilizing can cause salt build-up in the soil. Poor feeding can lead to a nutrient deficiency. Check your Miracle Gro label and adjust accordingly. Keep in mind that indoor tomatoes are unable to drain nearly as thoroughly as those planted in the garden outdoors. Nutrients have nowhere to go but the pot.
Indoor pests. Aphids commonly attack indoor tomatoes. You can control them by applying a steady stream of water (preferably in the bathtub or outside on a warm day!), yellow sticky traps, organic insecticidal soap like
Safer, a horticultural oil like neem oil, or any combination of these methods.