Sowing in February in NW London is about as early as most things benefit from. I have tried sowing onions in January and light has not been sufficient to advance the germinated seedlings well. Tomatoes develop well from January, but without a greenhouse they are ready to live outside in early April, which is often too cool to allow successful fruit set.
However, a few years of experimentation has identified some crops which benefit from a February sowing:
- Early tomatoes, aimed at producing a harvest in June and July (prior to the late July to late September main crop). I sow Maskotka and Red Alert in early February – the feature image above shows a 100% germination of my own seeds within 5 days, which are actually three years old!
- Onions, this year Kelsae (which produce very large bulbs) and van Rijnsburger (which store well).
- Boltardy Beetroot, the only beetroot which does not bolt with such an early sowing (aiming for crops in June and early July).
- Medania Spinach and Greyhound Cabbage, for harvests in May and early June.
- Ishikura Salad Onions, whose seeds I source from Quickcrop.
Over the years, I have tried out a variety of composts for seed germination. I have regularly used the John Innes series for tomatoes (as they pot on you go from JI Seed to JI One to JI Two before final potting out) and last year tried out Klasmann-Deilmann’s professional seed compost. This appears very expensive, but it really does germinate seeds fast, reliably and efficiently. It can be sourced much more cheaply by the pallet (around half the price of a single bag), hence buying groups will benefit hugely if sourcing this product.
The other reliable method I have used involves using Soil Blocks. How to make them is a subject in itself, and will form a new blog article later this spring. I use them routinely for germinating radish, Ishikura salad onions and used them successfully last year for Sweetcorn.
Mostly now, however, I carry out my sowings in 40 module trays (the exceptions being Kelsae onions and tomatoes, which I germinate in trays and then pick into small pots).
This year, my spinach and cabbage seedlings became long and thin (leggy) and so were transplanted into small pots with the stems below the soil surface, to allow them to become more sturdy. On a small scale, this is mildly irritating, but no commercial operation could condone such extra use of compost, time etc. So ensuring that seeds germinate well without producing leggy plants is one of February’s key challenges.