Tomato Troubleshooting

This year, Scott Daigre will sell 75,000 tomato seedlings for the Tomatomania events he produces on both coasts, including one this month at San Diego Botanic Garden. 

The owner of Ojai-based Powerplant Garden Design says, “I’ve seen it all” after 22 years in business: tomatoes shedding leaves or blossoms, tomatoes with yellow and brown leaves, tomatoes that don’t produce, tomatoes with split fruit, tomatoes infested with tiny aphids and giant horn worms. His most common diagnosis for troubled tomatoes: too much fertilizer and/or water. 

“Both are big mistakes,” Scott tells growers who attend his classes during Tomatomania. “Remember, tomatoes are greedy, not needy. Don’t over-coddle them. If you do, you’ll get lush green plants, but little or no fruit.” Scott’s preferred feeding schedule is once when first planted and again when the plants flower. Use a balanced tomato and vegetable fertilizer according to package directions. 

“Water deeply and infrequently, every four to five days in mild climates,” he says. “You want to soak the root ball. As the plant grows, you’ll water longer; and when temperatures heat up, more often.”

Here are his Scott’s tips for troubleshooting various tomato woes.

Yellow Leaves — “This is very frustrating, since there are probably a hundred causes,” Scott says. Yellow leaves could result from a lack of sun as the growing plant shades lower leaves and they wither. They could signal too much water, so check soil moisture and adjust your watering schedule if needed. Or they could indicate a fungal disease; remove the leaves and if the decline continues, shovel prune the plant.

Blossom Drop — Days that are too cold, too hot or too windy are likely culprits. The plant will flower again when optimal weather (55-90 degrees) returns. Another possible problem is overfeeding that causes the plant to emphasize foliage over fruit production.  

Brown Leaves — Pests like spider mites and aphids are likely causes of curled, crisp leaves. “If you see bugs, get those leaves out of there before there is a major infestation,” says Scott, who avoids using pesticides. No insects in sight? Diseases like blight or wilt may be problems. “Yank that plant and replace it with disease-resistant varieties,” he recommends. Replacement plants with the initials VFTN on their tags are good choices. VFTN means the plant is resistant to verticillium and fusarium wilts, tobacco mosaic virus and nematodes.

Cracked or Split Fruit — Too much water all at once is the problem. “It kills flavors, upsetting the acid-sweet balance,” Scott says. “A little stress on the plants as fruit ripens can intensify flavors.”

Tomato Hornworms — Well camouflaged, these hungry green caterpillars leave a trail of munched leaves and black frass. Look for them on the end of branches and pluck them off. “Or hang a feeder in the garden to attract birds,” Scott says. Another solution is to spray with Bacillus thuringiensis, a bacterium harmless to humans but fatal to hornworms. Find it at area nurseries.

By Mary James