Planting tomatoes: when, where & how

Growing tomatoes is a fantastic way to experience delicious and homegrown produce. Find out all about growing and planting tomatoes, whether in a greenhouse, outside in the garden or in pots.

Tomatoes (Solanum lycopersicum) are one of the most rewarding plants to grow and they come in a range of shapes, sizes and colours. The diversity in size alone ranges from small cherry tomatoes to big beefsteak varieties. Anyone who grows tomatoes will agree that the taste of a tomato freshly picked off the plant far outweighs any you can buy in the shops.

When to plant tomatoes

Tomatoes are commonly grown undercover in a greenhouse or polytunnel, but they can also be grown outdoors during the summer.

Tomato plants are regularly seen for sale in garden centres, but they are usually limited to a few staple varieties that growers have known and loved for years. However, there is a huge selection of tomato varieties out there to choose from, including heirloom cultivars, and these may be good options to try growing tomato plants from seed.

Tomato seeds are sown indoors from late-January through till the end of March. Read our step-by-step guide on sowing tomato seeds to learn all about it.

Tomato seedlings are pricked out when they are around 5cm tall into small separate pots filled with nutrient-rich soil to grow on. Soon, they will be ready for planting outside. There are a couple of signs for when to plant tomatoes outside: seedlings are 15 to 20cm tall and have at least four true leaves. Once the seedlings meet these requirements, you can harden the tomatoes off before planting them outside.

Wait until the last frosts have passed in your area, typically mid to late May, before planting tomatoes outside. To mature properly, a tomato plant tends to need around eight weeks of growth and a good level of light and heat. Tomatoes grow very poorly when temperatures are below 10 °C.

The best time to plant tomatoes outside is when the temperature is at least 15 °C. Ideal temperatures for growing tomato plants are between 15 and 32 °C. Planting outside too early in cold temperatures will not pay off; the plants will not get enough sun, heat and nutrients and will be generally unhappy. A cold spell will stunt growth and may even kill them.

If you are growing your tomatoes in a greenhouse the same rules apply. However, it means you can plant them earlier, once the greenhouse is at least 15 °C inside, and benefit from a much longer growing season.

Where to plant tomatoes

The best location to grow tomatoes is in a greenhouse, as it allows for a longer season and gives more of a guarantee for a great crop. A heated greenhouse can allow for the earliest crops, while an unheated greenhouse or polytunnel will result in fruits in mid-summer. Outdoor plantings will bear tomatoes in late summer.

If you are growing tomatoes indoors, they can be grown either in the soil, in a pot, or in a grow bag. If you want to try growing tomatoes in pots, use pots that are at least 30cm wide, as the plants grow quickly, becoming very tall and large, and do not respond well to their roots being restricted.

An ideal location for growing tomatoes outdoors is warm and south-facing to ensure the plants get as much warmth as possible. Do not plant tomatoes in a frost pocket, and make sure they are sheltered from the wind. Wind can make a big difference in temperatures, and tomato plants will not react well to cold winds. In colder areas, grow the tomato plants against a wall or fence to take advantage of any extra heat that comes from the structure.

Tomato plants thrive in fertile and nutrient-rich soil, as they are hungry plants that grow quickly. The ideal soil for growing tomatoes is well-draining and fertile with a pH of 5.8 to 7. Work well-rotted compost or manure into the soil to improve the structure and add nutrients, providing a slow-releasing food for the tomato plants for a longer period.

How to plant tomatoes

Planting tomatoes is a very simple process that requires very little tools. Once you have chosen a good site with lots of light and warmth for the tomato plants, it is time to plant them in their final home. All you will need is a trowel, tomato seedlings and some well-rotted manure or compost.

Planting tomatoes outside

When planting tomatoes outside, it is important to prepare the bed well. Remove any weeds and incorporate a lot of well-rotted manure or garden compost into the area. Dig deep holes or a trench to plant your tomatoes into; space tomato plants 45 to 80cm apart, depending on the size of the cultivar.

Plant each tomato deep into the hole, deeper than it was previously planted in its pot. Planting tomatoes deeply encourages more roots to develop. So, plant deeply up to the first set of leaves.

Water the tomato plants in well and mulch around them with well-rotted manure or garden compost to both retain moisture and add some extra nutrients into the soil to help the plants grow.

Tomato plants will need a support structure put in place, so get the canes, cages, or strings attached when planting. Learn more about training your growing tomatoes with our article on supporting tomato plants.

Summary:

• Add well-rotted manure or compost to the site
• Space your tomatoes 45-80cm apart
• Bury the plant’s roots deeply
• Water well and add mulch
• Add a climbing support and tie in the plant

Planting tomatoes in pots

Most varieties of tomatoes can be grown in pots but as mentioned earlier, make sure the pot is big enough. Use a pot that is at least 30cm wide with good drainage holes in the bottom. The larger the pot, the easier it will be to look after the plant.

Fill the pots with nutrient-rich compost. Here, it is best to use a compost designed for growing tomatoes, as it will have all the nutrients required. Our Plantura Organic Tomato And Vegetable Compost is perfect for growing tomatoes in pots. It is peat-free, organic, and provides your plants with nutrients to help ensure a fantastic harvest. Do not use soil from elsewhere in the garden, as it could contain soil-borne diseases and weed seeds. Unless it is a very large container, plant just one tomato plant in each pot.

The compost in pots dries out a lot quicker than soil in the ground, so keep a close eye on your plants and water regularly. This is especially the case on sunnier days. A layer of mulch, such as well-rotted manure or garden compost, will help reduce water loss.

You can grow certain varieties of tomatoes, such as trailing types or bush varieties, in hanging baskets. Remember that tomatoes are hungry plants, so regular watering and feeding will be vital if you are planting tomatoes in pots or hanging baskets.

Planting tomatoes in grow bags:

Growing tomatoes in grow bags has been a popular practice for many years. It is a simple, convenient, and effective way of planting tomatoes. A typical grow bag available from a garden centre holds around 27L of compost and is large enough to accommodate two tomato plants. You can buy specific grow bag watering kits or even self-watering kits for grow bags that can make looking after your tomatoes even simpler.

Organic Tomato & Vegetable Compost, 40L

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• Perfect for tomatoes & other vegetables such as chillies, courgettes & more
• For strong & healthy plant growth as well as an abundant vegetable harvest
• Peat-free & organic soil: CO₂-saving composition

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Care tips for growing tomatoes

After planting tomatoes, there are several key maintenance tasks that if done well will give you strong plants and a bountiful harvest. Consistent watering is crucial for tomatoes. They are hungry and thirsty plants and will benefit from regular and consistent watering. This will help avoid splitting fruits and diseases such as blossom end rot.

Feed your tomato plants weekly with a liquid tomato feed or high-potash fertiliser, such as our Plantura Liquid Tomato Food. Start this when the plant starts to flower and continue on a weekly basis.

Liquid Tomato Food, 800ml

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• Perfect for tomatoes & other vegetables
• Liquid fertiliser for healthy plant growth & an abundant harvest
• Quick & easy application - child & pet friendly

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If you are growing indeterminate tomatoes, and not bush varieties, keep an eye on side shoots and pinch them out on a regular basis. When fruits appear on the first trusses, remove the leaves up to that point to allow light and air to get to the fruits. Read our article on pruning and pinching out tomato plants to learn more.

Once four or five trusses of tomatoes have formed, chop the top off the tomato plant to stop the upward growth. This will concentrate the plant’s energy into ripening the fruits rather than continuing to grow upwards.

Tomato diseases

Keep an eye out for signs of common tomato plant diseases, such as tomato blight (Phytophthora infestans) orleaf mould (Passalora fulva), both are fungal diseases that can affect plants. Tomato leaf mould is a common problem with greenhouse tomatoes, causing yellow blotches on the leaves as well as grey mould growth. It is caused by moist atmospheres, so it is best to avoid getting water on the leaves and to remove any affected leaves immediately. Tomato blight primarily affects outdoor tomatoes, and spreads through the foliage and fruits. There are blight-resistant cultivars available, but any infected material must be disposed of, and tomatoes or potatoes should not be grown in that soil for at least four years due to the potential risk of reinfection from blight spores.

Are you inspired to try growing and planting tomatoes at home? Find out more about growing tomatoes in greenhouses in our expert article.