Tomatoes – April 2017 Plant of the Month

Tomatoes are by far the most popular home garden crop – and taste is the reason why. Nothing beats the taste of a perfectly vine-ripened tomato! Whether you have the space to grow rows of in-ground plants or only enough for a few container plants, growing your own is a fun and easy way to enjoy the delectable harvest that only a homegrown tomato offers.

Varieties

The iconic tomato may be round, red and softball-sized, but there is a lot of variety in the world of tomatoes. You can choose from varieties with fruits as tiny as marbles or ones with fruits weighing several pounds. In addition to the classic red-orange hue, fruits of various varieties ripen to orange, yellow, purple, green, striped – even white! Vines size ranges from a foot and a half high to six feet high or taller. With all this bounty, how do you choose? Here are some things to keep in mind to help you choose the best tomato varieties for your garden.

  • Growth habit. Depending on the variety, the growth habit of a tomato plant falls into one of three categories – determinate, indeterminate, or semi-determinate. Check the seed packet, plant label, or catalog information on the growth habit of a variety.

Indeterminate tomato plants continue to grow taller and set fruits throughout the growing season, stopping only when frost finishes them off. Many of the tasty heirloom varieties fall into this category. The continued fruit set makes them ideal for gardeners who want a regular supply of fresh tomatoes for the table. These large vines need sturdy stakes, cages, or trellises to support all that growth.

Determinate vines grow to a particular height, usually under 4 feet; then set their fruits within a relatively short time period, usually over several weeks. The smaller plants need less in the way of support than indeterminate types and are a good choice for container growing. Determinate varieties generally ripen the earliest, making them well-suited to short-season parts of the country.

Semi-determinate varieties fall in between. Like determinate tomatoes, they only grow to a certain height, often a little taller than determinate varieties. But, like indeterminate varieties, they continue to produce new fruits all season long.

  • Hybrid or open-pollinated. Hybrid tomato varieties are the products of modern breeding programs. These varieties are created through controlled pollination and have been bred for specific traits, such as increased disease resistance and greater and more uniform fruit production. If you plant seeds saved from a hybrid, they won’t come true, meaning they won’t produce plants like their parent.

Open pollinated varieties are the result of pollination by natural mechanisms. The result is plants with more genetic diversity than hybrids. Tomatoes are self-fertile, meaning that the pollen produced by the anthers in a tomato flower can pollinate the stigma of the same flower, but the action of bees and wind help to move the pollen successfully within the flowers. The seeds of open-pollinated tomato varieties do come true and can be saved from year to year, if you choose.

  • Heirlooms. These are generally defined as varieties that are more than 50 years old and have been passed down through generations of gardeners. Many gardeners feel that these open-pollinated varieties have the richest tomato flavor.
  • Fruit type. Large beef-steak types are great for slicing, while cherry and grape tomatoes are perfect for snacking or tossing in a salad. Meaty paste-type tomatoes cook up into delicious sauces and are good choices for canning and freezing.
  • Temperature and length of growing season. If you garden in a part of the country with a short growing season, look for varieties that mature quickly and that have been bred to set fruit well in cool weather. High temperatures can also interfere with fruit set, so if you garden where summer day temperatures regularly soar to the high 80s and 90s and night temperatures stay above 75 degrees F, choose varieties bred for heat tolerance.
  • Disease resistance. Look for varieties bred to have resistance to nematodes (N) and diseases such as verticillium (V) and fusarium (F, FF, FFF) wilts, and tomato mosaic virus (T), indicated by the appropriate letter after the variety name. Resistance is not immunity, but will decrease the chances of some disease problems.

Site: Full sun is best in many parts of the country, but if you garden in the warmest areas, such as the low desert Southwest, the Deep South and Texas, try to choose a spot where plants will get some light or filtered shade in the afternoon. Tomatoes do best in moderately fertile, moist but well-drained soil. Choose a spot that allows for ample spacing between plants, as good air circulation will help to reduce disease problems.

When to plant: Start seeds early indoors 6-8 weeks before you plan to set plants in the garden. When seedlings have their first set of true leaves (what appears to be the second set; the first are seed leaves), transplant to 4-inch individual pots if you started seeds in flats, or thin to the strongest seedling if you started seeds in individual pots. Make sure seedlings get plenty of bright light. Growing seedlings under fluorescent lights rather than on a window will help you produce stronger plants.

Set young plants (either homegrown or purchased) out in the garden when the soil is warm and all danger of frost is past, usually a couple of weeks after the last spring frost date. Be sure to harden off transplants for 7-10 days before you plant them outside.

If your goal is the earliest harvest, you can set some plants out 2-3 weeks earlier and give them some protection. (Don’t put all your plants out early because it’s still something of a gamble.) Pre-warm the soil in the beds by covering it with black plastic for a couple of weeks prior to planting time. Then surround each plant with a cage wrapped in clear, heavy plastic sheeting; cover with a floating row cover; or place a commercial product such as Wall-o-Water around the plant. Provide some extra covering on especially cold nights. Be sure to remove this protection once the weather warms so you don’t “cook” your plants.

Gardeners in long-season areas may be able to grow two crops. Plant the first crop in spring and harvest before the hottest weather hits. Then set out another round of transplants about 3 ½ months before the date of the first fall frost for a fall harvest.

Planting: Some type of support is needed for tall, indeterminate varieties, and even the shorter determinate varieties will have fewer disease problems and be easier to harvest from if given some support. There are lots of options for supports, from individual stakes to trellises to cages. Be sure to put supports in place at planting time to avoid damaging roots later on.

Stakes: Sturdy, 8-foot tall stakes work well to support indeterminate varieties, with at least 12 inches of the stake anchored in the ground, while 5-6 foot stakes are adequate for determinate varieties. Set plants that will be staked at least 18-24 inches apart.

Cages: Cages work well to support determinate and semi-determinate varieties. Cages should be at least 4 feet tall and 18 inches wide; even taller and wider if you plan to cage indeterminate vines. Be sure to secure the cage to two stakes driven into the ground on either side of the cage to prevent it from toppling over as the vine grows and becomes top-heavy. And make sure the openings in the cage wire are at least 6 inches square so that you can reach in with your hand to harvest your tomatoes. Set caged plants 3-4 feet apart.

Trellis: There are lots of possible designs for supporting tomato vines with a trellis or fence that work well for both indeterminate and determinate varieties. One simple setup is to sink sturdy posts into the ground at 5 foot intervals and staple support wire to the posts. Use either three to four wires running horizontally about a foot apart, starting a foot off the ground, or 6-inch wire mesh. Plant your tomatoes in a staggered pattern 3-4 feet apart on either side of the trellis and weave the stems through the wires as they grow.

When you are tying tomato stems to their supports, be sure to use a soft material that won't damage the stem tissue, such as pieces of old panty hose, strips of soft cloth, or thick, soft twine. Especially when tying up the succulent, newest growth, wrap the ties in a figure-eight to lessen the chances of the stem rubbing against the ties and getting injured.

Tomato plants have the ability to sprout new roots along the length of their stems. When you set young plants in the ground, bury the stem up to the first set of leaves to encourage this extra root formation. Place cutworm collars around the base of seedlings at planting time to prevent these night-feeding caterpillars from chewing through tender, young stems.

Care: Once the soil is warm (assuming you are not using plastic mulch), spread organic mulch over the soil in your tomato bed. This will help to keep weeds down, conserve soil moisture, and reduce disease problems by preventing fungal spores in the soil from splashing up onto lower leaves.

Keep plants watered consistently throughout the growing season to reduce problems with blossom end rot, a physiological disorder related to fluctuations in soil moisture. Even soil moisture will also reduce fruit cracking.

You don’t need to prune the suckers on your tomato plants to get a good crop, but pruning can be helpful at times. In general, determinate varieties do better with little or no pruning, since they are smaller plants and removing suckers may take away too much foliage and leave ripening fruits vulnerable to sunscald. Removing suckers on larger indeterminate varieties can help reduce fungal diseases by improving air circulation and light around the leaves. Where are the suckers? Look for the side shoots that arise in the angle between the leaf stalks and the main stem. When they are a couple of inches long, just reach in and pinch them off with your fingers by gently rocking the sucker back and forth until it breaks off.

Clean up and dispose of all plant debris in the tomato patch at the end of the season. This will reduce the number of overwintering insects and disease spores that will be around to cause problems the following season.

Troubleshooting:

No fruit set: Flowers dropping off without setting fruit are often the result to temperature extremes. If it’s too cool (below 55 degrees F at night) or too hot (daytime temperatures above 85-90 degrees F; night temperatures above 75 degrees F), plants may not set fruits. When the weather moderates, fruit set will begin. Too much nitrogen fertilizer can result in lots of deep green foliage and few flowers and fruits.

Catfacing: Tomato fruits that are puckered with corky brown strips of scar tissue form when something interferes with the normal development of the flowers, such as cold temperatures or drought. It is common on the first fruits of the season. Don’t set out plants too early when the weather is still cool, and keep soil moisture consistent throughout the growing season.

Cracking: This occurs when tomato fruits enlarge too quickly as they ripen. The cracks usually occur at the stem end of the fruit. Sometimes they form concentric circles; sometimes they radiate out vertically. When tomato fruits are at the mature green stage and the water supply to the plant decreases, the outer layer of the tomato skin begins to thicken. If the plant's water supply increases again suddenly, as when heavy rain follows a period of drought, the fruits enlarge rapidly and this tougher outer layer of skin cracks. Some varieties, especially some of the older ones, are especially susceptible to cracking. To control this problem, select crack-resistant varieties; try to keep soil moisture consistent by watering regularly, especially as tomato fruits are maturing; and make sure the soil around the plants is well mulched.

Blossom end rot: The blossom end of the fruit (furthest from the stem) turns black and leathery. This is the result of a lack of calcium in the fruit as it is forming. Usually there is plenty of calcium in the soil, but the roots of the plant are not able take up enough due to factors such as a sudden decrease in soil moisture, root damage from cultivating too close to the plant, or planting in cold, heavy soil. To control this problem, try to keep soil moisture consistent; mulch plants to conserve moisture and keep weeds down; and wait until the soil is warm before planting.

Late blight: The first sign is the appearance of dark, water-soaked, irregularly shaped spots, about the size of a nickel or a quarter, on the leaves. These spots become covered with a fuzzy white mold on the undersides of the leaves. They enlarge quickly, turn black and kill the entire leaf. The infection then spreads to the leafstalks and main stem, eventually causing the entire plant to collapse and die. Tomato fruits can also be affected. If you see spots on just a few leaves, you can pick these off, put them in plastic bags and toss them in the garbage. But if lots of leaves or the stems are infected, it's best to destroy the whole top of the plant to prevent the spread of spores to uninfected plants.

Tomato hornworm: These huge, green caterpillars chomp on the leaves and fruits of peppers and eggplants, as well as tomatoes. Because they are so large, even a few hornworms can consume a lot of plant, so it's important to control them if they turn up in your tomato patch. Keep an eye out for the newly hatched caterpillars; when they're small they blend in easily with the foliage. You may see their black droppings on the leaves. When caterpillars are under about 2 inches the microbial insecticide Bt will control them. Once they are larger than this, control them by handpicking. Cultivating the soil in late fall will help reduce the number of overwintering pupae by exposing them to birds and cold weather.

Harvesting: When tomatoes have reached full color for the variety you are growing and they have a little give when gently squeezed, they are their peak for picking.

Don't panic if the weatherman predicts light frost and your tomato vines are still loaded with green fruit. Often if you protect plants from an early light frost, the weather will turn warm again and you might get as much as several weeks more for green fruits to ripen. Protect plants by covering them with medium to heavy weight row cover fabric, old sheets, and the like before the sun sets; then remove coverings in the morning. But if hard frost is predicted, it's best to harvest what's left on the vine.

Also, once nights remain consistently below 50 degrees F, it's best to harvest any remaining mature green tomatoes (those that are at least 3/4 of their full size and have turned glossy light green to white), even if the vines haven't yet been hit by frost. These tomatoes will ripen better indoors once the weather is this cool. Clip tomatoes from the vine with a short piece of stem attached. Partly red tomatoes well on their way to ripening tolerate cooler temperatures and can be left on the vine until frost threatens.

Indoors, place the tomatoes on a shelf and cover them with sheets of newspaper or wrap the individual tomatoes with newspaper or waxed paper. The wrapping helps trap the ethylene gas tomatoes naturally give off that hastens ripening. Tomatoes need warmth, not light, to ripen, so there's no need to put them on a sunny windowsill. Keep them out of direct sunlight —in a spot where the temperature is in the 65-70 degrees F range. Proper humidity is also important during the ripening process. If it's too dry the fruits will shrivel; too humid and rot will set in. Placing individually wrapped fruits together in a covered box often works to keep the humidity level around them at a suitable level. To stretch out your indoor "harvest" over several weeks, keep some tomatoes at 55-60 degrees (no colder than 50 degrees) to slow the ripening process. Every few days check the fruits and remove ripe ones or any that have begun to rot.

Want a novel way to eat tomatoes? Try this recipe for Tomato-Peach Cobbler from Eating Well for dessert tonight!

FUN FACTS

  • Tomatoes are both fruits and vegetables. From a botanical perspective, they are fruits because they develop from the ovary at the base of the tomato flower and contain the plant’s seeds. But from a culinary standpoint, we usually use them vegetables because they are savory, rather than sweet.
  • The tomato is the official state vegetable of New Jersey. Arkansas covers its bases – the tomato is its official vegetable and official fruit!
  • Tomatoes are native to South America and were first cultivated as a food crop by the Aztecs in Central America. Their name for tomatoes translates as “plump things with a navel.” Following Spanish explorations in the New World, tomato cultivation made its way around the globe, not only to Europe but to Asia as well, via Spanish settlements in the Philippines.
  • The leaves of tomatoes are toxic. This may be why people were initially reluctant to eat tomato fruits when the plants were first brought to Europe in the 15th century.
  • The heaviest tomato, according to the Guinness Book of World Records, weighed 7 pounds, 12 ounces and was grown by a gardener in Oklahoma. The record for the most tomatoes harvested from one plant was set at the Epcot Center at Disney World in Florida – 32, 194 individual tomatoes weighing close to 1152 pounds all together!