How to grow tomatoes from seed, transplant tomato seedlings to your garden, condition the soil, the best supports for tomatoes and the essentials of mulching.
Hands down the most popular garden vegetable in the world is the tomato. It’s estimated that there are about 7500 varieties, from the Arkansas Traveler to the Zorba, in a multitude of shapes, sizes and flavors. Some tomatoes are open pollinated (OP) heirlooms whose seeds can be saved and passed down through generations; others are hybrids (F1) whose seeds, unlike heirlooms, won’t necessarily express the same traits of the parent plants.
The “perfect tomato” is literally a matter of taste – one person’s Beefsteak is another’s Cherokee Purple. The climate in your region will play a significant role in which tomatoes grow with abandon and which bear only modest fruit.
Many techniques, tips and tricks for growing tomatoes are handed down generation to generation. Every gardener has the method they swear by, but regardless of climate, cultivar and whether it’s determinate (bush-type) or indeterminate (vine-type), these guidelines will get you on your way to growing perfect tomatoes.
Know the last frost date for your area
Frost kills tomatoes, so knowing your last frost date is critical. See my post on how to find your first and last frost dates.
Think of the last frost date as your line in the sand. It’s the date after which you’ll plant seedlings. Where I live in Pennsylvania, the last potential frost date is May 14 and I rarely plant tomatoes before then, unless the spring is unusually warm. The tables are remarkably accurate-last year, the last frost in my area was only a few days prior to the 14th.
If you’re tempted by early warm weather to plant before the last frost date, make sure that seedlings are covered at night with plastic milk jugs, because even without a frost, cold nights and cool days can wreak havoc on exposed tomato seedlings. Gardeners using row covers or garden tunnels can plant weeks earlier, as the covers keep frost off the seedlings and add roughly ten degrees to air temperature inside the tunnel.
Starting tomatoes from seed
If you want to grow tomatoes from seed, start them indoors eight weeks before your last frost date. Tomato seeds germinate best in starter pots warmed with a heat mat, but they’ll also germinate at room temperature, but may take two or three days longer.
I start seeds in 4″ square or round peat or plastic pots, because I have the best results when seedlings stay in the same pot from germination to transplant. Not having to transfer seedlings from seed trays to pots minimizes stress on the roots, which can disrupt growth or damage the plant.
Sow 2 or 3 seeds in each pot and cover with 1/2″ of additional potting medium. Moisten the top of the starter mix with a spray mist bottle, then cover the pots with a sheet of clear plastic or a clear plastic dome to create a greenhouse effect.
Keep pots covered with plastic until seeds germinate in six to eight days, then remove the plastic to prevent mold or fungal infection. Water as needed, but don’t allow the soil surface to become dry.
When seed lings are about two inches, select the healthiest in each pot and snip off the unwanted seedlings with a garden snip or very sharp scissors. Do not pull unwanted plants from pots, as it may disturb the root zone of the seedling you wish to keep. Tomato seedlings need lots of light from this point forward, so move pots under grow lights.
Transplanting tomato seedlings
Plant seedlings in your garden bed on a cloudy day after your last frost date – cloud cover helps the seedling to adjust to sunlight and avoids early sun scald. But first, harden them off outdoors one week prior to planting, so they can adjust to night and day temperature fluctuations. A covered porch which receives morning sun and afternoon shade is ideal.
Plant seedlings so at least four inches of the plant’s stem is buried in soil. This encourages deep rooting, which will protect your seedlings during a drought or heat wave. Tomatoes can actually create additional roots from any part of the stem buried in soil.
If you’re supporting your plants with a tomato cage, wooden stake, or other device, plant the seedlings 15 inches apart in a straight row down your raised garden bed. If you will not be supporting your plants, allow 24 inches for determinate varieties and 36 inches for indeterminate varieties.
Soil and fertilizer
Tomatoes prefer soil that is light, with lots of organic matter and a pH range of 5.8-7.0. I mix lots of tree leaves into the bed in fall, compost in early spring, compost around the plants after transplanting and then twice more throughout the season. Supplement the compost and leaves with a feeding of fish emulsion or liquid seaweed every two to three weeks.
Use grass clippings, straw, pine mulch or pine bark to mulch tomato seedlings immediately after transplanting, and maintain mulch levels throughout the growing season. Mulch should be two to three inches deep and come to within one inch of the stem. This keeps roots well insulated in case of a heat wave, suppresses weeds, and helps to maintain adequate moisture levels. Keeping the mulch away from the stem helps prevent fungal buildup from excess moisture.
Supporting indeterminate tomatoes
Indeterminate (vine) tomatoes will grow just fine without support, but you’ll lose a lot of fruit to soil-borne pests and moisture. Get the fruit in the air.
In my experience, a tomato cage is useful for bush varieties, but useless for the long vines of indeterminate plants. Late in the season, when the plant is producing copious amounts of tomatoes, the vine will grow over the top of the cage and down the other side, creating a pinch in the vine, which restricts fruit development. To avoid this, “cap” the top of the plant with pruners when it reaches the top of the cage.
Wooden garden stakes are the tried and true, best means of support for tomatoes in a backyard garden. Tie the vine to the stakes as necessary with short pieces of fabric (wire ties cut into the stems). Make sure that you plant the stake at the same time you plant the seedling – this avoids root damage down the road. Trellising and training tomato vines overhead are quite effective as well, and are the preferred methods of commercial growers. Overhead support allows the vine to climb, but proper pruning with these methods is absolutely necessary and best left to experienced hands.
Read part 2 of How to grow tomatoes