April 12, 2002

Growing Tomatoes In The Home Garden

Approaching spring means planning home gardens for many people, and one of the most popular vegetables for master gardeners and novices alike is tomatoes. "Nothing beats a home-grown, perfectly ripe tomato for flavor and nutrition," says Ron Smith, extension horticulturist at North Dakota State University. "It can be grown in a traditional garden, a windowsill garden, or in individual containers. You don’t need to be a farmer to enjoy this healthful, delicious vegetable."

Smith offers pointers to help gardeners produce a successful tomato crop.

Nothing beats sunshine for good tomato production, he says. A gentle, south-facing slope would work best, heating the soil faster for early transplanting, and keeping it warm for maximum production throughout the growing season. Trees can pose a problem, both from the shade they cast and from root systems competing for nutrients and water. If roots are a problem, dig a trench around the perimeter of the garden and insert heavy roofing paper, copper screening, or aluminum sheeting, to block their invasion. Smith suggests.

Tomatoes require ample organic matter, moisture, and good drainage to be productive. The site should be throughly worked up and compost or other suitable organic matter incorporated as uniformly and deeply as reasonably possible.

"Tomatoes do not suffer cold temperatures very well, and unfortunately, northern gardeners are short of patience while waiting for spring to arrive," Smith says. Consequently, tomatoes often get planted too early and experience a delay in fruit development and reduced total production.

The single biggest mistake northern gardeners make is sowing the seeds for their garden too early so they either become rootbound or leggy. Tomatoes can be started four to seven weeks before transplanting outside. Be sure to provide adequate light for the seedlings. The light plants receive on a windowsill is often insufficient and may lead to leggy growth. Consider setting up fluorescent lighting just a few inches above the tops of the seedlings for healthier, more compact transplants.

Be sure the medium the seeds are germinating in is sterile or at least pasteurized to avoid damping-off fungus. Don’t over-water, and if possible, provide a little air movement across the seedlings to keep fungus diseases from developing. When the seedlings have developed their first set of true leaves, they are ready for transplanting into containers for planting outdoors.

Transplant tomatoes when a frost-free period can be anticipated for the growing season. To get a jump on the season, many experienced gardeners will pre-heat the planting site with plastic for about a week prior to planting, then set the plants out with plant protectors if the temperatures remain cool. Use that time of soil warming to "harden off" the plants prior to setting them out. Begin with just an hour the first day, and gradually increase the time until they spend most of the day outdoors in above-freezing temperatures.

Plant tomatoes deep. Tomatoes will have a nice fist of roots in the containers they were started in and can be set 2-4 inches deeper than that, depending on their size at planting time, Smith says. Any leaves that would be buried at the chosen depth should be pinched off. At planting, give each plant a good watering in, along with a cup of compost tea or a shot of garden fertilizer such as Miracle-Gro.

Planting distances depend on the variety and whether or not the plants are to be pruned and staked. If pruned to one stem, trained, and tied to stakes or a trellis, plants may be set 18 inches apart in 3-foot rows. With pruning and staking the fruit is easier to find and cleaner, and cultivation and weed control are easier. Staked tomatoes tend to have a greater incidence of blossom-end rot than those that are allowed to vine and grow naturally.

Uniform watering is important for healthy fruit development. Cycles of dry/wet cause splitting, fruit abortion, and in some cases blossom-end rot. Tomato plants will thrive best under a drip or micro-irrigation system and fertilization as they start to set fruit.

Cull any plants that show disease symptoms to keep disease spread under control. Regular crop rotation is important; cycle tomatoes and their family members (pepper, eggplant, and potato) out of the same planting site for at least three years. Rotations with beans, cabbage, or a root crop like carrots or beets would be a good choice.

The selection of tomato types is almost endless, says Smith, including early, mid, and late season; oxhearts, beefsteaks, and pastes. "There are small-fruited cherry and grape tomatoes, bi-colors and heirlooms. Everybody has their favorites," he says.

"Generally, paste tomatoes are used for sauces and salsa, while slicers are use for making salads and sandwiches. Cherry tomatoes are used in salads or simply eaten out of hand, while the beefsteaks are grown for full flavor and bragging rights. Unless you happen to be hooked on heirloom tomatoes, consider recent All American Selection winners for gardening purposes. These are grown every year in our trial gardens and usually perform very satisfactorily across the state."

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Source: Ron Smith, (701) 231-8161, ronsmith@ndsuext.nodak.edu
Editor: Gary Moran, (701) 231-7865, gmoran@ndsuext.nodak.edu