There's a lot to be said for planning ahead with your seeds if you want to yield good results
Now is the time to start planning and sowing seeds for your vegetable garden. At RHS Garden Rosemoor we have already started by sowing (indoors) the first hardy spring crops: spring cabbage, carrot ‘Amsterdam Forcing’, lettuce, peas and broad beans are all sown in a protected environment on the nursery. For fine seed we use our own mix of seed compost consisting of our potting compost with added super-coarse perlite to increase drainage.
Large seeds, for example peas and beans, are put straight into our peat-free potting mix; peas in gutters (right) and beans in 7cm (2¾in) pots.
When sowing small seed, e.g. lettuce, we use one litre pots then prick out into cell trays (cabbages also go into 7cm (2¾in) pots). We aim to plant these crops out into the garden at the beginning of April, weather permitting.
Come March we start the bulk of our seed sowing. It is tempting to start them earlier, but our tunnels are not heated in the day - so it is often damp and cold and we are likely to get damping off. This fungal disease can easily devastate pots of newly-germinated seedlings and to help prevent this we sow into clean pots, avoid overwatering and sow at the correct density.
If you look at the back of a seed packet, it will tell you the number of seeds it contains. Lettuce can have up to 200 seeds so just sow what you need and keep the rest back for successional sowings. For some seeds, e.g. parsnips and parsley, the germination rate can be increased by soaking or keeping them well watered. Early in the year we give our seedlings bottom heat, but as the weather warms up this becomes unnecessary.
Some seeds such as beetroot, spinach and chard are sown directly into modules, which reduces pricking out. Tender vegetables cannot be planted out into the glasshouse or garden until after the last frosts which, here at Rosemoor, can be mid-May.
Tomatoes, peppers and chillies are sown in March but cucumbers, courgettes, squashes, sweetcorn, runner and French beans are sown as late as April or they will be ready for planting out too early. So, get planning and you'll have plenty of home-grown veg to eat this year.