What’s Wrong With My Tomato?

Sun-ripened tomatoes easily earn their keep in even the smallest garden patch. But growing the perfect tomato can prove somewhat elusive. Flip through our gallery to diagnose your tomato problems — and discover strategies to set your world of vine-ripened flavor right again.

Those dark, sunken spots on the bottom of tomatoes are blossom end rot. It's so common that in tomato circles they call it BER for short. It's not a disease but a symptom of calcium deficiency. It occurs due to uneven watering (wet-dry cycles in soil), too-high nitrogen or root damage. You can eat tomatoes with BER — just cut the bottoms off. For a quick fix, treat plants with a calcium spray for BER. Keep soil consistently moist; using mulch helps. Test soil when tomato harvest ends. Amend as needed.

When tomato plants look healthy and flowers appear but drop without setting fruit, it's usually not your fault. Blame this one on the weather. When day temperatures linger around 85 F to 90 F and nights stay above 75 F, tomato flower pollen becomes unviable. Once the hot spell passes, flower pollination will resume and tomatoes will form. Until then, keep plants well-watered and fertilized, so they're ready to jump back into production. In regions where summer sizzles, grow heat-tolerant varieties, like 'Solar Flare', 'Summer Set', 'Heatmaster', or 'Phoenix'.

A cracked tomato means that while the fruit was ripening, the water supply was uneven. A heavy downpour that soaks soil can result in roots sending huge amounts of water to ripening tomatoes — so much so that they pop their skins. Cracked fruit is edible, but the cracks are more susceptible to mold. Eat ripe, cracked tomatoes before ones with smooth skins. Prevent the condition by mulching soil and watering tomatoes deeply twice a week, instead of giving plants a little water every day. When heavy rainfall is in the forecast, pick tomatoes that are almost fully colored.

Small holes in tomatoes are usually caused by slugs. The problem is, once slugs open a hole, the tomato weeps juice, and soon other critters join the party, like pill bugs, fruit flies and wasps. The wound in the fruit also invites early decay and mold. Slugs attack low-hanging fruit first, but they also slime their way up tomato vines and supports. Research slug treatments and adopt several strategies to deal with them. When tomato season is done, before frost, continue to use slug treatments to kill adult slugs before they lay eggs.

If you're discovering half-eaten tomatoes or ones with bite marks, you're likely dealing with squirrels or chipmunks. These critters are notorious for clambering onto plants and taking a small bite out of fruits. Usually they're after the water in the tomatoes, which is why they don't eat the whole thing (although sometimes they do). A pet dog or cat does the best job of keeping these varmints away from your produce. Some gardeners distract the critters with treats set out just for them — in a remote corner of the yard.

Protect ripening fruit by swaddling it with plastic bird netting. This treatment keeps nibbling rodents (squirrels, chipmunks, mice) at bay, along with birds and wood turtles, who love to snack on low-hanging fruit. Cut small pieces of netting and wrap it around coloring fruits. Store netting pieces in the garden clipped to tomato supports.

Hot summer sun can burn tomatoes, causing a condition known as sunscald. It's not much different from a sunburn on your skin. Sunscald results in a white patch that has very thin skin. The flesh beneath doesn't taste good. The problem occurs when there aren't enough leaves to shade fruit. Staking tomatoes or using cages helps leaves to dangle and cover fruit. Use care when pruning tomato leaves. Make sure you don't remove all the leaves that shade ripening tomatoes.

Finding holes in leaves and missing leaves? You likely have a tomato hornworm at work. These large green worms can gobble a mature tomato plant almost overnight. The worms hide under leaves during the daytime. Get rid of them by visiting your tomato patch at night, when they come out to feed. Knock worms into a container of soapy water. If you see a worm with white tic tac-looking things sticking out of it, leave it alone. It's been attacked by a parasitic wasp, and it's on a death march. You want those white eggs to hatch and release more wasps into your tomato patch.

Classic anthracnose symptoms include circular, water-soaked spots with a dark bull's-eye. A mold-like fungus eventually develops. Anthracnose is caused by a fungus that lives in soil. It's more prevalent in poorly drained soil. Leaves or tomatoes that come into contact with soil can pick up the fungus spores. Rain and overhead irrigation can also splash fungus spores onto plants. To avoid this disease, improve poorly drained soil by adding organic matter. Stake plants to keep them off soil, and pick tomatoes before they become overly ripe, which makes them more susceptible to the disease.

When tomatoes are weirdly deformed, that's known as catfacing. It usually happens on the bottom end of the tomato and results from cool temperatures (50 F to 55 F) during pollination. Usually when temps fall that low, tomato flowers drop from the plant. But if a blossom has been pollinated and the evening is unusually cool, the flower can get stuck on the newly forming tomato. The stuck-on bloom doesn't allow the tomato to enlarge and form freely. This typically occurs on tomato plants that are tucked into soil too early in spring. It also happens in cool-weather regions when late summer evenings dip into chilly fall-like temps while plants are still bearing fruit. Catfacing doesn't affect tomato flavor, so you can still eat the deformed 'mater. Just cut out the brown, woody parts.

Dark spots on leaves with concentric rings followed by yellowing between spots are a sign of early blight, a tomato disease caused by a fungus. It occurs on lower leaves first; spots can also appear on stems. Control this blight by spraying plants with fungicide. Remove all fallen leaves and destroy them; do not add them to your compost. To prevent disease spread, avoid getting water on leaves and don't work with plants when they're wet. Early blight is contagious and winters over on plant debris. Destroy — do not compost — infected plants at the end of the season.

Late blight is another fungus disease on tomatoes, and it appears as water-soaked spots on leaves, fruits and stems. It's a death sentence once it attacks a plant and usually spreads quickly to other plants. Track the disease spread by region online, and start treating your plants with fungicide when it occurs in your area. Destroy infected leaves and plants; do not compost them. To help prevent the disease, space tomato plants so they have good air circulation and avoid overhead watering.

When your tomato plants are all leaves and no flowers, there's likely too much nitrogen in the soil. Nitrogen fuels leafy growth, and when it's abundant, your plants will have lush growth with dark green leaves. Your soil likely lacks phosphorus, which helps trigger flowering and fruit formation. Tomatoes are heavy feeders and benefit from receiving specialized tomato fertilizer, which is usually higher in phosphorous (the middle number on the fertilizer bag). It might read something like 2-3-1.