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How to Grow Tomatoes Part 1: Starting Seeds to Transplanting

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.

tomatoes
Tomatoes on the vine in my garden.

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 tomato seedlings, 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.

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.

Tomato seedlings set out early are covered by milk jugs, which protect them from frost, cold nights and hungry rabbits

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 pots or plastic pots. You can also start in small pods and move them to larger pots after they outgrow the starter pods. This is called “potting up”.

Sow 2 or 3 seeds in each pot and cover with 1/4″ 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 place your pots in a plant tray and cover it with a clear plastic dome. The plastic cover keeps your potting medium from drying out and maintains consistent moisture throughout.

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growing tomatoes from seed
Starting tomato seeds in fiber pots

Keep the pots covered with plastic until seeds germinate. usually within six to eight days, depending on the age of the seed and the variety of your tomato. After germination, remove the plastic to prevent mold or fungal infection. Spray mist the potting medium once a day, but don’t allow the surface to become dry.

When seedlings develop their second set of leaves, it’s time to thin the seedlings to 1 per pot. Look for the one which appears healthiest – growing straight, good color, no sign of damage, etc. With a very sharp scissors or garden snip, cut off the rest of the seedlings at their base. Do not pull unwanted plants from the pots, as it may damage the roots of the seedling you wish to keep. Tomato seedlings need lots of light from this point forward, so move pots under grow lights. If you lack grow lights, an extremely sunny room may also suffice. Windowsills are hit or miss and you may end up with a ‘leggy” plant – very thin, with few leaves.

Tips on planting tomato seedlings in your garden

Before planting your seedlings, harden them off outdoors one week prior to planting. This helps them adjust to night and day temperature fluctuations and avoids transplant shock. A covered porch which receives morning sun, afternoon shade, and protects the seedlings from wind is ideal. When they’re hardened off, plant your tomato seedlings in your garden bed on a cloudy day after your last frost date – cloud cover helps the seedlings adjust to sunlight and helps avoid early sunscald.

tomato seedling
Tomato seedling about 10 weeks after germination.

Planting tip: Remove all of the lower leaves on the seedling and just leave the upper foliage and the foliage just below it on the plant. Dig a hole as long as the plant and lay the seedling in this hole with the leaves and about 4-inches of stem above ground. Make sure the roots are thoroughly covered and below the soil surface. The tomato plant has the unique ability to grow roots from anywhere on its stem, so take advantage of this trait to avoid injury from drought and high winds.

If you’re supporting your plants with a tomato cage, wooden stake, or other means, plant the seedlings at least 15 inches apart in a straight row. If you will not be supporting your plants, allow 24 inches for determinate varieties and 36 inches for indeterminate varieties.

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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 compost into the garden bed in early spring, compost around the plants after transplanting, and then twice more throughout the season.  Supplement the compost with a feeding of fish emulsion or liquid seaweed every month.

Mulch tomatoes

Use untreated grass clippings, straw, pine mulch or pine bark mulch to cover the soil immediately after transplanting and maintain mulch levels throughout the growing season. Mulch should be two to three inches deep and come to within two inches of the stem. This keeps roots well insulated in case of a heatwave, suppresses weeds, and helps to maintain adequate moisture levels. Keeping the mulch away from the stem helps prevent fungal infections of the stem or accidental damage to the plant.

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. To maximize your yields, get the fruit in the air.

The old school method in my garden: Tomato seedling tied to a tomato stake.

In my experience, a tomato cage is useful for bush varieties but not 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 my preferred method of support. Tie the vine to the stakes as necessary with short pieces of fabric like ribbon, shoelaces or garden twine. Make sure that you drive 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: Watering, Harvesting, and Saving Seeds 

6 thoughts on “How to Grow Tomatoes Part 1: Starting Seeds to Transplanting”

  1. Hello! I just would like to give a huge thumbs up for the great info you have here on growing tomatoes. I wish I could write it that clearly. Thank you.

  2. Malcolm Griffiths

    this is a really great blog you have here; good honest advice.

    I always remember my father putting straw in the bottom of the trench he would dig every year for his tomatoes. Not sure why but we still do the same these days!

    Keep up the good work Todd!

  3. I just found your site today and it’s lovely. I moved to North Carolina from Idaho over the summer and had to leave my raised garden beds behind. I managed to plant tomato and basil in a couple of pots at our new rental, but deer teem all over the place down here and one night they ate the four large green tomatoes that were just about to ripen. Now I’m not sure if I’ll plant anything next summer since our yard here is not fenced in and don’t want to put the effort forth to do much to our rental. I may resort to trying those topsy-turvy planters!!! Anyway, I’ll be back to read more of your posts as I have the time. Gardening is an interest I would like to learn more about and your site seems very well-done.

    I blog about teaching, writing, and traveling at jeriwb.com

    1. A friend of mine had a Greek boyfriend and went to live on the island of Corfu, where she also learned to grate tomatoes. Apparently her boyfriend’s family looked at her strangely when she attempted to chop them! But I have tried this too and as well as getting a really nice texture you seem to get a fresher flavour too . . . or maybe that’s wishful thinking on my part after grating my fingers too!

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