March is quite possibly the busiest month in the greenhouse calendar.
A huge variety of seeds can be sown during the merry month of March, to such an extent that you risk filling your greenhouse benches with pots of seeds and seedlings before you get to April.
Greenhouse gardening and seed sowing is an addictive past time and once you’ve started sowing and growing and built a little confidence there's little that can slow you down.
The reason March is such an important month in the greenhouse calendar is because it takes most tender plants about 10- 12 weeks to grow from seed and be large enough and ready to harden off in a coldframe and then plant outside.
Work backwards from a safe sowing date of around mid to late May and you arrive back in March.
Of course it varies from plant to plant, but that’s why there are instructions on the seed packets.
It can be a bit confusing as some plants such as greenhouse tomatoes can be sown from January under heat and you can still sow them in March and April. The logic here is that if you heat your greenhouse or have heated facilities for growing on early sown and tender greenhouse plants like tomatoes then you can start them off in January.
Many greenhouse gardeners do not heat their greenhouses and wait for the power of the sun to take off the chill and facilitate sowing a few weeks or months later. If they are desperate for an early crop many resort to buying two or three ready grown tomato plants from mail order specialists or from the garden centre, allowing their later sown plants to catch up and produce a later crop.
There are lots of tips with regard to sowing seed. One of them is not to sow all the seed at once. Just because you started sowing in march for an early crop need not negate the possibility of sowing more seed in April or May for a later crop.
This is so often overlooked in pursuit of a harvest before the shops start selling British grown or when the produce is sold at a huge premium, think new potatoes as one example, when they first come into the shops they are extraordinarily expensive reflecting the effort that goes into producing an earlier crop.
Some crops like herbs, salads, carrots and even beans are best sown in succession.
With a greenhouse you can give them a protected start and sow them early for a first crop, then if you’ve got enough seed and the secret here is to check the plant count on the seed packet and opt for varieties that offer dozens of plants per pack rather than just a handful and sow maybe a fifth at each sowing.
If you sow fortnightly, for example, then you add ten weeks to your harvest season, as the plants will generally mature gradually over the space of 2-3 months.
If you want to extend it further, with crops like salads and herbs then split the packs further or experiment with different varieties to vary your salad bowl and ring the changes.