To get a bumper crop, stagger planting dates to extend the tomato harvest (see Harvest vs. Planting Date). Staggered transplant times will also reduce pest and disease problems, though it may not be an option if you live in an area with a short growing season. For people with longer, warmer growing seasons, start with a small crop — just one or two plants — and then add plants as the season progresses. That way, you’ll have an early, mid and late harvest rather than having your crop come in all at once. (Check our listing of tomato varieties by growing season, which will help you find the right tomato for the right cultivation time.)
Wait until soil temperatures are at least 55 to 60˚F and days are in the 60s before transplanting your tomatoes. You can get them out earlier if you keep them warm using something like an insulated cloche, cold frame or row covers, but if you put them out too soon, you won’t gain anything.
Hardening Off: Preparing the Plants
Whether your seedlings are store-bought or home-grown, you’ll need to harden them off before transplanting them into your garden. Hardening-off means getting them accustomed to the colder and more changeable outdoor environment by setting them outdoors in the shade during the day, and bringing them back in (or at least covering them) at night.
Many people who know about protecting young plants from night’s chill are unaware that they also need to be protected from the shock of full-sun. Putting them in direct sunlight before they are ready can give your tomatoes the equivalent of plant sunburn. So start with shade and progress to partial sun before subjecting them to full sun (see Hardening Off Isn’t Hard).
Hardening should take anywhere from seven to ten days. This transitional time should leave the plants ready for transplanting.
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Cultivating: Preparing the Soil
The term cultivating may bring to mind heavy machinery, but that isn’t what we’re discussing here. The other image that leaps to mind — hoeing in the heat of mid-summer to keep the weeds back — is also not at issue. Mulches and close spacing pretty much make hoeing unnecessary. No, the only cultivating recommended here is pre-season soil preparation. If you’re planting, for the first time, in an area of loose, super-rich, well-drained soil, you can skip this step. If, however, you are mortal, then your soil will benefit from additives.
That said, it should also be noted that the days of mandatory deep digging are on their way out. Improved understanding of soil structure has led to a decreased enthusiasm for breaking up that structure and disturbing highly beneficial earthworms. A good rule of thumb is therefore to dig only on a need-to-dig basis. You need to dig if:
• you are starting a new plot
• you are working an old, tired plot that has not received soil amendments regularly
• your soil is heavy and clayey
• your soil is extremely sandy
• your soil is extremely anything — alkaline, acidic, stony, dry, heavy.
But if you have an established plot with good, light soil, you probably only need to mix your soil amendments with compost and spread them on top of the plot.
The single, key, always helpful addition is compost. Not only is it rich in nutrients and beneficial micro-organisms, but it also improves soil texture, and that means that it increases both moisture retention and drainage (see Benefits of Using Compost). Note that not all “organic matter” is compost. Peat moss, wonderful for helping soils hold moisture and for making it lighter and easier to work, does not contain many nutrients, and coconut fiber, a similar additive, contains none. Undecayed vegetable matter (kitchen scraps, lawn clippings, fallen leaves) contain many nutrients, but most are not readily available to plants until they have been broken down. Some manures, wonderful for gardens after they’ve been allowed to stand for a year or so, can actually damage plants if applied too soon (see Manure: Is It Safe For Your Garden?). Mature, fully decomposed compost is the way to go.
Beyond the “use compost” dictum, most soils benefit from materials that add the three main nutrients plants need. One easy trio is blood meal (nitrogen), bone meal (phosphorus) and greensand (potassium).
Quick Guide to Amendments for Problem Soils
For very sandy soil: Sandy soils drain very quickly, so you need to add material that help the soil hold water long enough for plants to get at it. Organic matter in any form will do this, but coconut fiber, derived from the coarse outer fibers of a coconut, or peat moss, harvested from bogs where it acts as a giant sponge, are especially effective. The other obvious candidate would be the old standby compost, which provides a complex array of nutrients as well as improving water-retention.
For very clayey soil: Clay soils consist of very fine particles which first resist absorbing water and then retain it tenaciously. Like sandy soils, heavy clay soils tend to be low in organic matter, so again, compost is the first line of defense, followed again by coconut fiber or peat moss. If your soil is neutral to acidic, coconut fiber may be the better choice of these two, as it tends to have a higher pH (5.5-6.3, as opposed to peat moss’s 5-5.3). In very heavy soils, however, adding sand may be as important as adding organic matter.
For acidic (low pH) soils: (below 6 — i.e., you are planting under a pine tree): First, do not despair. It isn’t true that nothing will grow under a pine tree. Even tomatoes will grow under a pine tree if they receive adequate compensation in the form of high-alkaline additives like lime or wood-ashes. “Under,” however, is a relative term: if you’re talking about a blue spruce whose branches sweep the ground, then the dictum holds true. If, however, you’re talking about a lodge pole pine whose branches start eight or ten feet up and grow almost straight out, then yes, you can probably plant under it about ten feet from the trunk. The problem is as much water and light as it is acidity.
For alkaline (high pH) soils: (you live in the west, where rainfall is low): Once again, start with compost, as alkaline soils generally lack organic matter. Beyond that, any of several additives will help correct this problem, and you can choose between them on the basis of their other qualities. Elemental sulfur, which is sold in the form of small “split-pea” pellets, will add the essential plant nutrient, while peat moss will add organic matter.
Seedlings are ready to plant outdoors when they are about six inches tall. Cloudy days are best for transplanting tomatoes (video), as seedlings are less likely to dry out or to suffer from sharp temperature changes. To transplant, pinch off the lower leaves. For those of you who started your plants from seed, this is just what you did when transplanting seedlings into larger containers.
Note: Bathe plants with a weak solution of compost tea before transplanting. Dousing them with a super-strong, synthetic fertilizer can send them into some botanical version of shock, so go light.
Before you put your tomato plants in the soil, put one cup of kelp meal and one cup of bone meal into each planting hole to give them a turbocharged start. Kelp is an excellent all-around plant nutrient, which is rich in micronutrients, while bone meal is rich in phosphorus, which promotes flowers and fruits. These are both slow release fertilizers which will provide nutrients over time, without sending plants into shock as might too much chemical fertilizer. Both are also rich in micronutrients. One trick old-time gardeners use is to add Epson salts — one to two tablespoons per hole — when transplanting tomatoes. Epson salts add magnesium, an important plant nutrient.
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Handle plants gently when transplanting. Any bruising or damage will set them back or leave them vulnerable to viruses or pests. Be careful to keep leaves free of dirt, as many fungi and viruses live in soil.
In the north, both the roots and most of the stem should go into the hole. Only the top leaf cluster should protrude above the ground. Since tomato roots will grow from the stem, the plant will have a larger root structure, which has two advantages: it gives the plant a more stable base, and it allows the plant access to more nutrients. In the south, it’s best to keep the same soil level, as the buried stem can be vulnerable to fungus. The longer growing season in the south also lets the root structure reach an optimal size without the deeper planting.
If the plants you are transplanting are tall and leggy, or if you are growing tomatoes in the north, you can use trench planting instead of the traditional hole method. The trench offers two advantages, neither of which is always relevant: you don’t have to dig as deep a hole, and the entire length of the plant’s root system is in the upper layer of soil, which warms up first in the spring and which usually contains the richest nutrients. Dig a horizontal trench as long as the roots and stem together. Remove all the leaves from the plant with the exception of the top leaf cluster. Lay the plant on its side in the trench and cover the root system and bare stem up to the top leaf cluster with two to three inches of soil mixed with kelp and bone meal. When you’ve filled in the trench, the part of the plant above ground will be lying on the dirt, but not to worry; it will become vertical within a few sunny days. If you want, you can gently push a rock under it to get it started in the right direction. This is an especially good idea if the weather is likely to be cloudy or rainy.
A third transplanting method involves digging a fairly large, deep hole (a foot wide at the top, tapering to eight inches or so, and up to a foot deep), and then planting the seedling at the bottom of it. As the plant grows, remove lower leaves, and gradually fill in the hole. This method makes maximum use of the tomato’s ability to root its stems, but it also puts the seedling in much colder earth than other methods do. To alleviate that problem, dig the holes a week in advance, and put a bottomless milk jug with the top still on in the bottom of each. The jug, acting like a miniature greenhouse, will speed the heating of the soil as well as preventing its collapse into the hole. When you transplant the seedlings, cover them with the jugs, but as soon as day temperatures reach seventy, remove the tops to avoid cooking your plants. Between the hole itself and the jug, a seedling is well-protected from wind, and as the exposed soil warms, it radiates warmth around all sides of the plant. This is an excellent technique to use in barrels and containers, where digging deep holes doesn’t involve much labor.
Because tomatoes love sun and heat, you can solarize their soil, covering the entire plot with plastic for the entire season. Soil solarization helps curb or prevent disease, especially verticillium wilt. It’s easiest to do this before transplanting, so that you’re not wrestling wads of plastic around delicate seedlings. Dig in your compost and nutrients, then wet the soil, lay down your plastic, and cut slits or Xs where you plan to set plants. If you are preparing holes with individually measured nutrients, it may be best to do that preparation before laying the plastic, keeping out only enough earth to cover the seedlings. Digging a hole large enough to hold two cups of fertilizer, then refilling it through holes in plastic can make an unholy mess. Just be sure to mark where the holes (and nutrients) are, so that you can cut your slits just above them.
In a warm climate, mulching with straw (not hay!) is another option. Charles H. Wilbur, who has spent his life producing record-sized vegetables using organic methods, including a Guinness Book of World Records tomato plant in 1987, uses wheat straw, and describes his method in detail in his book How to Grow World Record Tomatoes. In the north, though, straw and other insulating mulches are a poor early-season choice, as they keep the soil from warming up.
If you plan on staking tomatoes, it’s a good idea to put in the stakes at the same time you transplant. This pretty much eliminates the chance that you’ll drive a stake through the plant’s roots at some later time. Put the stakes on the downwind side of the plants, so that when the wind blows, plants are not straining against narrow bands of material, but instead lean into the long vertical support of the stake.
Some gardeners use In a cold area where there are any doubts about the possibility of frost, it’s wise to give seedlings some sort of cold-weather protection. This can take many forms. A plastic gallon milk jug with the bottom cut out can be set over each plant, providing a personalized greenhouse with a natural vent at the top. An old tire acts as a wind break. Floating row covers provide frost protection.
Wallo’ Waters, which are set on the ground with a seedling at the center and then filled with water. They act as effective insulators (protecting down to 16°F) as well as superb wind breaks, but can be tricky to handle until they’re full of water. Each Wallo’ Water encircles an 18-inch diameter area and should last 3 to 5 years.
Wallo’ Waters have a tendency to droop or tip when empty or half-full, which makes filling them difficult. On the other hand, when they’re full, they’re much too heavy to handle easily. It’s best to put a couple of inches of water into each tube before setting the Wallo’ Water in place, and then filling it gradually, not in a circular pattern, but going back and forth across the ring, so that one side never gets a whole lot heavier than another. (Click on Tips for Earlier Yields in the Home Vegetable Garden for more about Wallo’ Waters.)