You started seeds indoors in January and tended them lovingly until March when you planted them outside. All through April you’ve watered and weeded and fertilized and scouted. Now, finally, in May and June—it’s tomato time! As you begin to harvest your reward, you may have questions. Especially if this is the first time you’ve grown tomatoes in northeast Florida! Here are some things you can do now to keep those tomatoes coming!

Water Consistently

As we shift from our warm, dry spring to hotter and rainier summer weather, you may need to adjust your watering schedule. Remember that tomatoes need 1-2 inches of water per week, and that includes rain. Get a rain gauge if you don’t have one so you can track how much water your plants are already getting each week. Consistent watering will help minimize the chances of blossom end rot, caused by a lack of calcium in the developing fruit. Calcium moves with water through the plant, and if watering is inconsistent, calcium may not be in the fruit when needed–even if there’s enough in the soil.

Provide Support

If you staked and caged your tomatoes when you planted them, good for you! Now that they’re getting bigger, you may need to adjust. Use velcro ties or something similar to gently hold your main stem to a stake and keep it growing upright. This will help keep stems from breaking as fruits get heavier and keep the fruits off the ground. It’s not too late to install tall and heavy duty cages around indeterminate (vining) tomatoes. Anchor cages to the soil, and be sure the openings are large enough to get your hand–and tomato–through when harvesting.

Tall tomato plant surrounded by cage — Cattle panels can be bent into right angles, so two form a sturdy square cage around tall tomato plants.

A tomato stem tied to stake with velcro — Velcro ties support your stems without damaging them.

Fertilize Appropriately

Continue fertilizing once every 3-4 weeks if you have sandy soil; or every 4-6 weeks if you have clay soil. Use a complete granular product. A complete fertilizer has all three of the main macronutrients (nitrogen, phosphorus and potassium), and may have essential micronutrients as well. At the flowering and fruiting stage, try to choose one that has a lower nitrogen, or N number (the first one on the bag). If we supply too much nitrogen, we may end up with lots of beautiful tomato leaves, but not very much fruit. Using a product with 30% slow release nitrogen will help even out the delivery of nitrogen between fertilizer applications, giving plants a lower but continuous supply. And it will help ensure we don’t lose all the nitrogen applied in the first heavy rain.

Prune to Manage Size and Keep Plants Healthy

If your indeterminate tomatoes are getting too large and unwieldy, you can remove sucker vines that grow from leaf axils, where the base of the leaf meets the stem. This will direct growth to the main stem, making your plants less sprawling. It will also increase air flow, which can help prevent disease. The downside is that you may get fewer, though larger, tomatoes. If you leave the suckers, you’ll have a somewhat wilder plant, and more smaller tomatoes. In this case, a cage becomes even more important. Either way, you can remove lower leaves that are touching the ground to help prevent disease and increase air flow through the plant’s branches. Try not to remove leaves above the fruits. Leaves protect the fruits from becoming sunburned.

Tomato suckers growing in leaf axil. — Tomato suckers grow in the leaf axil, or where the leaf base meets the stem.

Keep Scouting

Once your plants are full and leafy and your tomatoes start ripening, the dinner call goes out to every hungry insect. Carefully observing your plants and fruits, and turning over leaves to look at the underside is essential to keeping your plants healthy and productive. Try to scout daily, perhaps in the early morning or evening when the weather is mild and you feel like being outdoors.

What are you looking for? For starters, see if there are holes in otherwise healthy looking leaves. Turn them over. Look below the holes for frass, or drops of poop. You may have caterpillars, which are lavae of many different kinds of insects. Common caterpillars in our demonstration garden are armyworms and hornworms. There are several species of armyworms, but they usually show up in very large numbers and can quickly overwhelm your plants if you’re not scouting for a few days.

Tomato leaves with holes in them. — Evidence of caterpillar damage on tomato leaves

Armyworms on tomato leaves — If you’re not paying attention, army worms can quickly overwhelm your tomatoes!

Hornworms are the very large green ones, that actually look pretty. Or would, if they weren’t so hungrily eating your tomato leaves. Hornworms are easy to pick off by hand, and you can even use a black light at night to see them better.

a green caterpillar on a plant stem — Tomato hornworm. UF IFAS

For armyworms (and insect larvae in general), products containing B.T., or Bacillus thuringiensis, are very effective and non-toxic to just about everything else. B. T. comes in both liquid and dust formulations. Read the labels of the products you’re considering to determine what’s best for your particular larval pest and growing situation.

Other common pests include aphids and whiteflies, primarily on the plants, and stinkbugs or leaf-footed bugs, primarily on the fruits. Aphids and whiteflies are tiny insects with piercing sucking mouthparts that they poke into tender growth and use like a straw to suck out the plant’s food. Aphids can be many colors, but adults are all little pear-shaped blobs on plant stems and leaves. You can spray them off with water, or treat with a horticultural soap or oil. Whiteflies are, well, little white flies. You may see them leaving the plant as you walk up. You can also use yellow sticky cards to monitor for them. Whiteflies can also be treated with horticultural soap or oil, and if you have them it’s important to treat. They can transmit plant diseases as they poke their “straws” into different plants.

Tiny insects on green leaves — Aphids are easy to spot and relatively easy to treat. Just spray them with water or use horticultural soap or oil.

tiny white flies on underside of leaf — Whitefly adults and young on underside of leaf. UF IFAS

This year, thrips and spider mites have been more problematic than usual in the demonstration garden. Both thrived in the hot dry weather we had in March and April. They are tiny and hard to see without tapping the plants and holding a white piece of paper underneath, but you can see spotting on leaves, or webbing from from the mites. Over time their feeding can weaken your plants and cause them to decline. Both can be treated with horticultural soaps or oils.

spider mites on leaf — Two-spotted spider mites are tiny arachnids and have 8 legs.

an insect on a highly magnified leaf — A thrips insect highly magnified.

Finally, look for stinkbugs and leaf-footed bugs, especially on ripening fruits. They too have piercing-sucking mouthparts, and they can damage the quality of your tomatoes. Both insects are relatively large and built like tanks. Insecticides tend not to be very effective. But they are relatively easy to catch and either stomp, squish, or throw into a bucket of soapy water.

Don’t Forget Diseases

In addition to scouting for insects, look for spots on leaves, yellowing leaves or twisted and distorted leaves. All can be signs of disease. Many diseases that affect our tomatoes are fungal, and they are spread through water. You can minimize risk of fungal diseases by using good cultural practices. Water plant roots and soil, not leaves; water in the morning so leaves that do get wet have time to dry early in the day; use clean tools when making cuts; and avoid touching, working in or walking between rows of plants that are wet with rain or dew. Other diseases are viral or bacterial, and can be spread by insects.

If you think your tomato plants have a problem and you can’t figure it out, call one of our Duval County Master Gardeners for advice. They are on duty at the UF IFAS Extension Duval County office Monday-Friday from 9:00 a.m.-3:30 p.m. If they don’t know the answer to your question, they will reach out to agents and other UF experts to figure it out.

leaves of tomato plant curling up — Tomato Yellow Leaf Curl Virus is transmitted by infected white flies. UF IFAS

Harvest Regularly

As you’re scouting, watering and fertilizing, also look for fruits that are ripening. The first ones will be lower and may be in the interior. Harvesting when fruits are just getting ripe will help you beat the insects (and other critters) to them. It will also help you avoid rotting fruit on or at the base of the plant. Both can lead to more disease pathogens. You can leave tomatoes on the counter or windowsill if needed to complete the ripening process.

Focused attention now will help you get the best harvest possible in May and June. This is important, because as our summer temperatures rise, many of the large-fruited tomato plants are no longer able to set fruit. The exception to this is cherry and grape tomatoes. They typically continue producing through the summer heat. In our demonstration garden we typically pull up our tomato plants once they are no longer productive around mid-July. So take care of those beefsteaks, mortgage lifters and trucker’s favorites–and enjoy tomato time!

For More Information See:

UF IFAS U-Scout for more on tomato diseases–with pictures
Tomato Insect Pest Management for more on how to treat insect pests
Tomatoes on Gardening Solutions
Cherry Tomatoes on Gardening Solutions

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