Getting the timing exactly right for sowing tomato seeds can be tricky. Sowing too soon means you have to nurture your plants until weather conditions are warm enough to plant them out, while late sowing can lead to a poor crop. Let’s figure out how to pick the optimum time to sow tomato seeds in the UK!
Sowing Tomato Seeds
Tomato seeds should be sown about 6-8 weeks before the earliest date they can be transplanted. This will result in healthy young seedlings that are the ideal size to plant out when weather conditions allow. Tomato plants need warmth and plenty of sunlight for vigorous growth and should not be transplanted until weather conditions are suitable for them to thrive.
To calculate the best tomato sowing dates in the UK, you need to count backward from your region’s last expected frost date. This can be as early as mid-April in southern counties, allowing you to sow seeds from mid-February onwards. For those in hillier northern regions, frosts can occur as late as the start of June, so hold off sowing tomato seeds until early April in these areas.
When sowing tomato seeds, the aim is to time it so that your seedlings are still in the early growth stage when planted out. This means they will have a sturdy root ball, the first true leaves will have developed, and the young plant will quickly become established in its new location. Transplanting larger tomato plants can lead to transplant shock, where growth is stunted for several weeks until the root network recovers from the move.
When To Sow For Growing Outdoors
In the UK, seeds for tomatoes intended to be grown outdoors should not be sown until late March to early April. This will allow the soil to warm up before tender seedlings are planted out in late spring or early summer, reducing the risk of transplant shock and frost damage.
Avoid the temptation to sow tomato seeds earlier if you want to grow them outdoors, as these delicate young plants will grow quickly and can become weak and leggy if light levels are low. Even a sunny windowsill or conservatory may not be sufficient to keep these plants in peak condition, and later sowings tend to be healthier and more vigorous than their earlier sown counterparts.
When To Sow Tomato Seeds For Growing Undercover
Seeds for tomatoes intended to be grown undercover in a greenhouse or polytunnel can be sown slightly earlier – from late February to mid-March is ideal. This allows for an extended growing season for these warmth-loving crops, with tasty homegrown tomatoes harvested from the greenhouse several weeks sooner than those grown outside.
Remember that overnight temperatures in a polytunnel or greenhouse can still dip as low as outside, so tender young transplants will need protecting with cloches or fleece until all risk of frost has passed.
