When should you plant out tomatoes? Gardening experts reveal the best timing for an impressive harvest
Give your ruby red fruit the best chance at prize-winning growth with this planting guidance
Despite being one of the most popular edible plants to grow at home, it can be quite confusing knowing when exactly is best to plant out your tomato seedlings.
Between knowing how to prune tomato plants and mastering the art of ripening green tomatoes once they're harvested, there's a lot more to growing this beloved fruit than you may think. And although they're relatively low maintenance and perfect for those beginning to grow vegetables, it's important to know exactly what they need, and when.
When should you plant out tomatoes?
In between sorting your garden out this spring, you might have a lot of plants that you've sown which are big enough to be planted out. Tomatoes belong on that list, but only if the weather is right.
"Once you've got night-time lows that are reliably 10°C or above for about a week, you'll be okay to plant out tomatoes. Repeated chilly nights slow root growth and can leave plants sitting still for weeks," says Dr Russell Sharp, Founder of Eutrema.
"Any frost will kill your tomato plants. Check local climate records to know when the last frost historically hits your area. Any temperature below 10°C will set them back, and you will notice the foliage turning 'blue' (an accumulation of pigments in response to stress)," he explains.
Protecting your plants from frost may seem dramatic at this time of year, but in the UK, the weather is unpredictable.
Dr Russell is an innovator, best known for developing the range of plant care products offered by his company, Eutrema.
Shop tomato potting essentials
This is a great tomato food to use in your garden. Just remember that it needs to be diluted before adding it to your plants. It's even enriched with seaweed extract!
These Gold Leaf RHS collections Chelsea Ladies Comfortable Leather Gardening Gloves are perfect for any job you need to tackle in your garden, even potting out your tomato plants.
This popular mix from Miracle-Gro can be used to plant flowers and seedlings in containers. It includes coir, which is great for absorbing water and keeping plants hydrated.
How to plant out tomato plants
Whether you want to grow tomatoes in pots to save space this season or add them to your thriving veggie patch, planting them out right is key for their growth.
"The aim is to avoid transplant shock and get roots growing straight away, since warm, active roots drive quicker flowering and better early truss development," starts Dr Russell.
"Start by hardening off for 7 to 10 days. Increase outdoor time gradually, including gentle sun and light breeze, and keep plants protected at night until conditions are mild, leaves and stems can be damaged and growth checked," he continues.
While tomatoes are not one of the best plants for shade, they do need to be protected from the elements in other ways.
"Choose the sunniest, most sheltered spot available, ideally with some wind protection, and make sure drainage is good. Tomatoes hate sitting in cold, saturated soil. Improve the planting area with well-rotted compost to help structure and moisture balance, then incorporate a balanced slow-release fertiliser so nutrients are available steadily without forcing soft, sappy growth," instructs Dr Russell.
"Water the plant in its pot beforehand so the root ball is fully hydrated, then plant deep, burying part of the stem up to the first set of leaves," he adds.
All that's left is making sure you're supporting your garden plant as it grows, that way your troota won't be damaged, and you'll have an impressively tall plant covered in delicious fruit come the summer.
How big should tomatoes be before planting out?
If you're a little unsure about the weather and are doubting its consistency, you can go off the appearance of your tomato plants instead.
"Size matters less than sturdiness and readiness. A good plant is typically 15 to 30 cm tall with a firm, upright stem that is closer to pencil-thick than thread-thin, and with several true leaves so it can photosynthesise strongly once outside," Dr Russell says.
"The root ball should be well-knit and hold together when eased from the pot, with roots reaching the edge but not circling densely in a tight mat. Badly pot-bound plants often struggle to take up water evenly after planting," he explains.
"It is fine if a first flower truss is visible, as long as the plant looks robust and has been hardened off properly, but if a plant is tall, pale, and stretched from low light indoors, it is better to correct the situation with deeper planting and a short delay until nights are consistently mild," Dr Russell finishes.
You might want to delay your planting out and add it to your essential gardening jobs for May, just to be on the safe side.
To make your life easier in the garden, we'd recommend trying out some companion planting in your vegetable patch. It can help you reduce the risk of pests and diseases, all whilst improving your garden's ecosystem.
