The sweetpea seedlings that I sowed in the polytunnel in September are now healthy seedlings, germination was 90% as opposed to the 50% germination of the seeds sown at the beginning of October. Just a couple of weeks difference, but the warmer weather must have meant faster germination and less time for the seeds to rot.
I sow two lots of seed - the first in September, the second in March. I soak the seeds in parafin overnight so that they will not be eaten by mice and then sow them, one to a cell, into root trainers. Root trainers are ideal for legumes which like a deep root run (though I now use them for most of my seed raising), they are long narrow cells with ribbed sides and an open base. The main root grows straight down until it reaches the open base, it then emerges into the air and the tip is killed off. This send a message for the root to branch at the top and send down more roots, which will again have their tips air prumed when they reach the bottom. The ribbed sides encourage the roots to grow straight down and you end up with a great strong, straight root system.
Today I raised the roottrainers up on plastic pot trays so that the air can get under them to begin the root pruning (otherwise they can end up rooting into any soil lying around the bench) and next week I shall tip prune them, nipping off the tops above 4 pairs of leaves. Eventually they will be potted up into 2 litre pots. The aim with overwintering sweetpea plants is to keep the leafy bit as compact as possible and let the roots grow strongly. Sweetpeas don't really mind the cold - I have had them survive -10 - but they hate sitting in wet soil, so they will survive happily in an unheated tunnel, greenhouse or coldframe. Overwintering makes a big difference to the end result, the seeds I sowed in September should be flowering from the end of May until the end of August and will grow to 10 feet tall if given their head.