Tomatoes are far and away the most popular vegetable grown in American gardens. Nearly unheard of only little more than a hundred years ago, they are grown now by eight out of ten American gardeners. Though all tomatoes are tender perennials grown as annuals, there is, nonetheless, a very wide range of plant and fruit types.
Tomatoes go in the second part of our crop rotation, while the soil is still rich but not too high in nitrogen. As with peppers and eggplants, too much nitrogen in relation to the available phosphorus and potassium will cause the plants to grow large, but bear few fruit. Some gardeners think that tomatoes, perhaps because they are perennials, don’t need to be rotated, that they do better when grown in the same spot continuously, fertilized with compost made from their own previous season’s foliage. My grandfather didn’t buy that reasoning, and neither do I: we change the tomato plot yearly and keep four years between successive crops in the same plot.
The most basic distinction among tomatoes is between the bush and vine types. Bush tomatoes are called determinate, because their genetic programming causes them to grow a certain number of branches and flower clusters and then stop, much the way that peppers and eggplants grow. Because of their fixed habit they are considerably less trouble to grow than vining tomatoes; they are generally earlier as well. But bush tomatoes are usually less disease-resistant, and their flavor will rarely match that of fruit from the larger plants; there just isn’t enough plant to produce as good a fruit.
For a more in-depth discussion of trellising methods, take a look at these short videos shot by Jim Surkamp at the Princess Street Community Garden in Shepherdstown, WV.
Intensive Gardening – Mostly Tomatoes[youtube=http://www.youtube.com/watch?v=kPoBCuX9R_8&rel=0]
Starting with broccoli, but focusing mostly on tomatoes, and the different methods of trellising them, as well as early transplant protection.
Tomato Update – A Month Later[youtube=href="http://www.youtube.com/watch?v=S3rRShyz90Y&rel=0]
This video shows the same tomatoes as the video above, about a month later, and goes into more detail about tomato trellising.
Indeterminate tomatoes are true vines. Being perennial they will continue to grow, sprouting new leafy and fruiting branches, until the plant is killed by disease or frost. I have seen eighteen-month-old greenhouse tomato plants fifty feet long, and, in long-season areas, some varieties trellised against the wall of a house may well climb to the roof! Trellising the plants can be a fair amount of trouble but it’s worth it, particularly if you have a small garden. With a bit of attention to training the plants, you can get them to bear almost as soon as a bush type, and really both bush and vining tomatoes should be supported, though each requires a different kind of trellis. When buying either tomato seed or plants, make sure you know which type you are getting.
In all but the warmest areas, tomatoes should be started indoors six to eight weeks before the last frost. We sow the seed 1/4 inch deep in 50-plug trays and germinate at 75-80F/24-27C. Transplant to successively larger cells or containers as soon as the leaves of adjacent plants touch, ending up with 18-plugs or 4 inch pots.
Many writers suggest an earlier start, but I feel that a younger plant (started later) will do better once out in the garden and quickly surpass one that has been held too long in the inferior conditions of the average south-facing window. A common mistake made by home gardeners who buy their plants is to purchase huge, spindly transplants complete with little fruits already forming. Nothing could be worse in terms of the plant’s adjustment to outdoor conditions: once it has begun to set fruit, its most vigorous vegetative growth period has already passed. In terms of productivity, you’d do better to hold off flowering a little while to give the plants time to put on plenty of foliage before they begin to bear. Research has shown conclusively that the best-tasting tomatoes are the ones borne on plants with the most foliage per fruit.
And even if those first few flowers produce early fruits, they won’t taste like much, and you are sacrificing the later productivity of the plants to get it. If you must, put in a couple of plants for early harvest; but don’t start your main crop of tomatoes too early. And if you buy, buy young, stocky plants, without flowers or fruit. A good tomato transplant should be at least as wide as it is high.
Tomato seedlings are grown just like other heat-loving plants, with one exception. Long study has confirmed that you can increase the number of flowers (and therefore fruit) on the first few clusters borne by your tomato plants if you lower the temperature they grow at (in the indoor flats) for the first three weeks after they have their true leaves. As soon as the seedlings have a first pair of serrated leaves, let the growing area cool down to 55F/13C at night, but keep it at 65F/18C or above during the daytime; continue this for three weeks, then go back to keeping the temperature at 65F or above at night as well. If this causes too many problems—eggplants and peppers won’t like it, so it means segregating the plants—don’t bother, but it is a little trick the bedding plant growers all use, and you can, too.
While the plants are hardening-off, prepare the bed as for other heat-loving crops: that is, lay drip irrigation tubing along the center of the bed and dump a shovelful of compost where each plant is to go, then cover the bed with a black plastic mulch to conserve moisture, exclude weeds, and prevent soil splash (which is one of the major factors in the spread of tomato disease). In cool and cold climates (USDA Zone 3-5) space the bush determinates 12-18 inches apart and indeterminate types 2-3 feet apart; farther south you’ll want to give the determinates 18-24 inches and the indeterminates 3-4 feet each.
Unlike peppers and eggplants, the transplants should be set considerably deeper than they were in the pot. In fact, after carefully stripping off the lower leaves, you should bury the vines up to within three or four branches of the top, or the first flower cluster, if one is visible. The buried part of the stem will then send out extra roots, which later in the season will help the plant supply the nutrients necessary for a bumper crop of tasty tomatoes.
We like to set small basil, parsley, or Gem marigold plants along the edges of the bed, alternating with the tomatoes, both because it makes more efficient use of the space, and because it looks nice. Some gardeners also feel this kind of interplanting makes for healthier, better-tasting tomatoes, and if so, so much the better.
Immediately after setting out the plants, I recommend covering them with a floating row cover. This will protect them from wind, sun, and temperature variation, plus keep out flying insects until they have established themselves. After a couple of weeks, remove the covers, store them neatly in a dark place for later, and set up the tomato supports.
As mentioned above, the two different kinds of tomato plants require two different kinds of support. Bush, or determinate, tomatoes can be grown in cages, simple wire or wooden enclosures two or three feet high and about eighteen inches across, which are simply stuck into the ground over the newly uncovered plants. They should be securely anchored against the wind, however. If a whole row is to be planted, a “Quonset cage” makes more sense. The plants grow up through the support, eventually all but hiding it, and—with its help—hold their fruit up off the ground, a great help in preventing fruit rots and the depredations of field mice, moles, and other crawling tomato eaters. That’s all there is to it.
If you don’t have the room to store the cages or quonsets, you can use what is called a “stake and weave” method for trellising. This works well, but requires more attention than the cages. Here is a quick video about how to stake and weave your tomatoes:
For vining tomatoes, we set up a trellis like that used for pole beans and tall peas, but string it differently. Instead of creating a mesh of string, run a single line for each plant up to the top bar. First, tie a nonslip knot about four inches in diameter around the base of the plant; then, before cutting it off the spool, run the other end of the line up and over the top bar. Cut it off about two feet beyond the top bar. Tie the loose end to the bar with a granny knot that will come out easily later, leaving a fair amount of slack between the top and the plant.
Once all the plants have been attached in this fashion, their training begins. If you look closely at how a tomato vine grows, you’ll see that it starts out as a single stem with leafy branches and flowering branches. But soon sprouts appear at the stem joint (called an axil) of each leafy branch, and begin to grow. Left on the plant they, too will produce both leafy and flowering branches; first, three leafy ones, then a flower cluster, then three more leafy branches, and so on.
This is important to the training of the plants. We can control how the plant grows, how many fruits it sets, and when, by our judicious pruning. After each of these axial stems reaches three branches, pinch off its growing tip to stop further development. That way, except for the axial foliage, which we want, we can keep the plant growing as a single stem. This makes it easier to trellis and keeps the number of fruit low in relation to amount of foliage, which makes for better-tasting fruit. It also ensures that each plant will get plenty of air—another factor that will help fight disease.
Some gardeners like to let the first sprout arising from the base branch of the plant grow out as well, giving them a two-stem plant. One benefit they see is that the extra foliage will help protect the fruit from sunscald. That’s hardly a problem in the North; the extra growth allowed on the axial stems can provide the same protection. I’d rather set more plants—the eighteen-inch spacing is as close as you’ll want to go—and limit each to just one stem; this way you get just as many stems in the same space, but each has its own root system to supply nutrients.
The actual training of the vine is simple. You just take the slack vertical string (which is loosely attached to the base of the plant) and wrap or braid it around the growing vine, a minimum of one wrap for each fruit cluster. As the plants get taller, the slack hanging from the top bar will be taken up, and the knot can be periodically released to make more twine available. This, as well as the pinching out of the axial stems, need only be done every week or so, and takes just a few moments per plant. Once the plants reach the top of the trellis, pinch out the growing point of the plant. That will cause it to stop growing and start ripening the fruit it has. If you want super-early fruit, simply pinch out the end sooner; yields will be earlier though smaller.
In tomato cultivars (in terms of the fruit) there are at least three types, and within each, a number of colors. All three types are available as either determinate or indeterminate plants. Cherry tomatoes have tiny fruits ranging in size from 1/2 inch to 1 1/2 inches in diameter and weighing only an ounce or so; they are juicy, often quite sweet, and great for out-of-hand munching. Salad, or slicing tomatoes are larger, from two to as much as six inches in diameter, and can weigh up to two pounds apiece; the larger ones are called beefsteak tomatoes. The third major class of tomato is the processing kinds, which are much meatier than either cherries or beefsteaks; their lack of juice makes them much better for drying or boiling down for sauce.
Pests of Tomatoes
The major pests of tomatoes are flea beetles (when the plants are young) and a large green caterpillar called the tomato hornworm. Flea beetles are easily outwitted by putting a floating row cover over newly set plants until they have a chance to get well established. Hornworms, if left unchecked, can make a real mess of your tomatoes, but are also easily controlled. Because they are so large, hornworms are not hard to find and pick off the plants by hand. If there are too many, Bacillus thuringiensis (Bt) is quite effective against them. If you find one that has a small white egg case “hitchhiking” on its back, though, leave it alone, as it has been parasitized by the tiny, predatory Trichogramma wasp; soon there will be many more of these beneficial insects.
There are some excellent reference books on organic pest and disease control, and it would be wise to add a few to your library; a full list of those that I recommend can be found in the Biblio.
Newer varieties of tomatoes are resistant to common tomato diseases, and this resistance is almost always noted in the catalog description. Look for these capital letters following the name or description: V means resistance to verticillium wilt; F means resistance to fusarium wilt; N means resistance to nematodes; and T means resistance to tobacco mosaic virus.
Verticillium and fusarium are long-lived soil fungi. Fusarium is favored by warm soil and verticillium by cold soil; both are best controlled by crop rotation and, if necessary, planting resistant varieties. Nematodes are small worms that live in the soil; some feed on plant roots, including tomatoes. Tobacco mosaic virus (TMV) is a mostly preventable disease of tomatoes that nonetheless claims a lot of casualties. A scourge of the whole nightshade family—which includes not only peppers, eggplant, and tomatoes, but also potatoes and tobacco—it causes deformed or mottled leaves, but is not always easy to recognize. Affected plants do not yield as well as healthy ones, and the fruits may be bitter.
The reason this virus is such a problem is that it is transmitted on the hands of tobacco smokers, and once established in your garden takes up residence in the soil, where it can persist for two years or more. Tobacco is a field crop; in the process of manufacturing, many, many plants are shredded and mixed together before being rolled into cigarettes. What this means is that each cigarette may have shreds of tobacco from many plants in it. These shreds will have come in contact with an even larger number. When you consider that a smoker is likely to have smoked many cigarettes over the course of two years, it is easy to see that the virus may well be in residence on his or her fingers.
If, at the greenhouse where you bought your tomato plants, they were handled by a smoker, there is a chance they will have become infected. Most greenhouses are very careful about this but it is also possible that the customer before you was a smoker and handled the plants before you bought them. The simplest prevention, which is used by many greenhouses, is to make sure that smokers who will be handling any of the plants in the nightshade family dip their fingers in a weak bleach solution (ten parts water to one part bleach) before first touching them. That will kill the virus. One important note: once TMV has infected your plants, you should not use them for compost; and do not plant any member of the nightshade family in the same plot for at least two years (a good idea anyway).
Weather conditions may create problems for your tomato patch, amplifying the effect of any disease or deficiency present in the soil. The most common disease of tomatoes, perhaps, is early blight, or alternaria. It is recognizable by brownishgray spots, with concentric circles within, that develop first on the older leaves, and then move up the plant. Infected leaves will eventually yellow, wither, turn brown, and fall off. Early blight is basically a foliage disease, and only in severe cases does it affect the fruit; but then, in severe cases, there may be little fruit to worry about. Early blight spreads when rain or irrigation splashes spores of the fungus from ground to leaf, and then from leaf to leaf. We have been able to control it almost completely through crop rotation and mulching to prevent rain splash; with drip irrigation there is no reason for irrigation splash.
Septoria leaf spot is another foliage disease favored by rainy weather. Its habit is somewhat similar to alternaria, but the spots are much smaller; its progress, results, and control are much the same. A somewhat similar problem, subject to a similar cure, and which occurs primarily in the South, is gray leaf spot. Another fungus, known as anthracnose, can cause serious fruit rots, but only following foliage disease, or if the fruit is in contact with the ground. Mulch helps prevent this.
There are also several fruit problems that can develop due to variations in moisture availability. Fruit cracking occurs when there are alternating periods of dry and wet weather. During a dry spell the skin of the fruits gets too rigid, and once good growing condition return it can’t expand fast enough to accommodate the swelling fruit tissue, and ruptures. These cracks then offer an ideal site for bacterial or fungal infection.
Blossom end rot occurs during dry periods when the lack of water creates a deficiency in calcium uptake. First the end of the tomato gets soft, then turns hard and leathery. Once this occurs, you might as well remove the fruit from the plant, as it will never recover. Blossom end rot is more prevalent among trellised tomatoes, because their upright, airy posture draws more water from the soil; but both this problem and cracking can be avoided by consistent watering with a drip irrigation line beneath the mulch.
Two final problems we have seen with tomatoes—and that may well concern you if they happen in your garden—are the premature abortion of the flowers, which fall to the ground without forming tomatoes, and grotesquely misshapen fruits. I’m afraid there isn’t much you can do about either except wait for the weather to improve. Flowers abort mostly because the temperature was either too high or too low for pollination to take place during the critical two-day period after they open, and the unpollinated flowers are simply discarded by the plant. Catfacing (a malformation suggesting a cat’s face) is caused by a disturbance of pollination that doesn’t halt it completely, resulting in fruits that develop unevenly. There is a similar malformation that occurs in strawberries, but is caused by insects.