When To Sow Tomato Seed

If you intend to grow tomatoes outdoors, sowing eight to ten weeks before your last frost date is ideal.

So if your last frost is expected around the end of May, you would sow (indoors) from the middle to the end of March.

If you are growing tomatoes in an unheated greenhouse, you could start a month earlier than above.

Knowing when to sow tomato seed is important In order to be successful.

Starting them too soon and the plants may be subject to conditions that are too cold and days that are too short. Sowing them late could mean that the season ends before the tomatoes have had time to ripen.

Grow Lights
Seeds may be sown earlier if you use a grow light to provide longer days, as it were, for the seedlings. Without extra light, seedlings can become very leggy (too tall with thin stems) and not be able to support their own weight.

Sow seed indoors around the middle of March to the end of April if you intend to grow your tomatoes outside. You cannot leave them outside overnight until all danger of frost is past which in most areas of the UK is estimated to be around mid to late May.

However, if I put my plants out at the end of May, I’ll cover them with garden fleece at night until night-time temperatures warm up a bit.

These seeds are about life size.

If your seeds are sown mid March, they should be about ready to go into their final pot or grow bag mid to late May… about 8 to 10 weeks after sowing.

It is best if your plants are almost in flower before you put them into their final position and new compost, or they will grow lots of leaves which may delay flowering.

When it says that a variety is 56 days from transplanting, it means that you should be able to pick 56 days after planting them in their final position.

I estimate that if you sow around the middle of March, plant in their final position in late May, you should be picking around the middle of July.

Tumbler (again!), one of my favourite varieties but becoming difficult to find. Red Alert is similar and also a good choice.
It is not essential that plants are in flower before planting in their final position. However, some gardeners may leave them until this stage (in smaller pots that restrict root growth) in order to force them on to the flowering stage more quickly.