Growing Tomatoes From Sowing to Harvest

How to Plant Tomatoes Inside and Outside

May 18, 2020

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We’ll show you how to plant tomatoes, whether seeding indoors, potting up, or transplanting outdoors. Plus, pay attention to a few pointers on tomato plant care from proper supports to pruning to direct energy into fruit production and a great harvest!

Types of Tomato

The first job is deciding what to grow, and with at least 10,000 different varieties of tomato, there’s certainly plenty to choose from, including cherry tomatoes, paste types, varieties with standard round fruits and chunky beefsteak tomatoes.

Whatever you grow, they’ll fall into one of two categories: ‘bush’ tomatoes, sometimes called determinate tomatoes, which grow to around three feet (1m) tall, and ‘vining’ tomatoes, also called indeterminate or ‘cordon’ tomatoes, which continue growing to produce fruits on one long stem.

Only got a hanging basket? Hey, no problem – there are compact tomatoes for this situation, too.

Where to Grow Tomatoes

Tomatoes love warmth and sunshine, whether grown in the ground or pots. Some varieties cope better with cooler climates than others, while heat-tolerant tomatoes are best suited to hot climates. Look carefully at variety descriptions and choose one that’s right for your garden.

Tomatoes need a soil or potting mix that’s rich in nutrients. Prepare beds in advance by incorporating plenty of organic matter such as compost or well-rotted manure to give the soil a boost ahead of planting time. Container-grown tomatoes need a particularly good quality potting mix, which may need topping up as they grow.

How to Sow Tomatoes

Many gardeners buy transplants (small plants) that were started by a garden center or nursery. 

If you are sowing tomatoes by seed yourself, you would need to sow in early spring 6 to 8 weeks before your last frost date. (Our Garden Planner can help you work out when to sow when because the sowing recommendations in the Plant List accompanying every plan you make are based on data from your nearest weather station.)

Okay, so let’s get sowing! Fill pots with seed or all-purpose potting mix then tamp it down to leave a smooth surface. Space seeds individually over the surface, about an inch apart. And then cover with a little more potting mix.

Move pots to a propagator or indoor windowsill. If you haven’t got a propagator cover the pot with clear plastic until after germination to create a humid environment around the seeds. Germination is quickest at around 7ºF, but I wouldn’t obsess about this. Seedlings will germinate on a windowsill without any special treatment whatsoever.

Once seedlings are big enough to handle, it’s time to transplant them into their own pots. Carefully remove the seedlings from their nursery pot and then, picking them up gently by the leaves, move them to pre-filled pots of potting mix. Make a deep hole and lower them in. Set them a lot deeper than they were growing before, so most of the stem is buried, right up to the lowest leaves. New roots will grow from the buried stems, helping to give sturdier seedlings.

If the young plants fill their pots before it’s time to plant them, pot them on again into larger containers.

Plant tomatoes in pots for growing under cover up to three weeks ahead of your last frost date. Use pots at least a foot (30cm) wide and set plants nice and deep. Again, bury the lowest part of the stem to help anchor the plant. It’s worth using bigger pots if you can – the extra potting mix means plants will need watering less often.

Pots are great for indoors or out, as are purpose-sold growbags like these. Planting into a bottomless pot placed on top of the growbag means the plants can produce more roots along the buried portion of stem, which helps it to draw up more nutrients and also provides a little more support.

Vining tomatoes will need full length supports. One method is to tie strong twine to the base of the stem or bury the end of the twine beneath the rootball at planting time, and suspend it from a horizontal wire up above.

Planting Outdoors in the Ground

Get young tomato plants used to the outdoors first (assuming they have been indoors or in a greenhouse by you or a nursery).

Before planting by leaving them outside for progressively longer over one or two weeks. Start by popping plants outside on a warm day for just a few hours and build up from there. Be very careful to avoid windy spots and bring plants back under cover on chilly nights.

Finally, plant them about 18 inches apart once the risk of frost has passed. See our Almanac Tomato guide for more planting information.

How to Support Tomatoes

Bush tomatoes can be supported simply by tying them in to canes or stakes.

Vining types on the other hand require regular attention. Weave the top of the stem around twine supports as they grow, or tie stems to canes using soft string. Add ties close to the trusses in order to lend extra support to heavy fruits. You can provide additional support for both types by growing inside a wire cage which will take much of the weight of the fruit as they grow.

Removing Side Shoots

Remove all side shoots from vining tomatoes – that’s any shoots growing between the the main stem and the leaves, a point sometimes referred to as the ‘armpits’ of the plant – to concentrate the plant’s energy on fruit production.

Inspect plants regularly and snap them off while they’re still young.

Stop vining tomatoes growing any further once they reach the top of the greenhouse or tunnel or, in more temperate climates, once they’ve set four to five fruit trusses to encourage them all to ripen before autumn. To do this, simply cut out the very top of the plant.

Caring for Tomatoes

Watering

Mulch outdoor tomatoes well to conserve water and hold down weeds. Water your tomatoes whenever the potting mix or soil starts to dry out.

Feeding

The first flower truss is your cue to begin regular applications of a high-potassium tomato feed, which will help to produce lots of good-sized fruits. Avoid high nitrogen which causes lush leaf growth at the expense of fruit.

Pollination

If you’re growing your tomatoes in a hoop house or greenhouses or tunnel, temperatures can soar on sunny days. Open wide vents and doors, which will ensure pollinators have easy access to go about their work too. Twanging or tapping supports also helps to improve fruit set.

Harvesting

When the fruits are ready, pick them! Go over plants regularly so you don’t miss any. Like many fruiting vegetables, the more you pick, the more plants respond by producing even more.

For more information on tomato plant care, pests, and harvesting, see our complete Almanac Guide to Growing Tomatoes.

Next Steps

Ready to get started? Our Almanac Garden Planner will automatically calculate your sowing dates, your plant spacing, and more. Plus, you’ll get a free printable calendar with planting and harvesting dates that fit you.

For new gardeners, we are offering a free 7-day trial to encourage all to try drawing out their first garden plot!

See the free trial of the Almanac Garden Planner!

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