Seed Sowing Tips

When to Sow

Seeds want to grow. Most seeds are very accommodating and the real question is when do you want the plants? Don’t be tempted to sow too early in the year. They won’t grow as well and you will have to look after them for longer before planting them out.


Can be sown in autumn (Sept-Oct) and overwintered under cover without heat (eg in a coldframe) for big plants early in the year. Or you can sow in spring (Mar-Apr) for smaller plants later. # - Seeds marked # on the packet will germinate much better if given a cold period (either naturally by sowing in autumn, or unnaturally by putting in the fridge for 2 or 3 months). They will then germinate as they warm up in spring. Seed must be damp during the cold period, dry cold will not do the trick. To avoid a fridge full of compost, you can mix the seed with damp vermiculite and put in a jar, after a couple of months just tip the mixture onto your seed compost.


Usually sown in late spring (May-July, about the time the seed would ripen naturally). Grow them on for the summer and plant out in autumn.


Almost always sown in the spring, usually best April-May. Early sowings often fail to grow well because light levels are not high enough yet. Keep seed of tender plants warm, at least 60-70oF. By May they will probably need no extra heat. Later sowings often grow better and can catch up with those sown 2 or 3 weeks earlier. You don’t want them ready to go outside till the end of May or the beginning of June.


or any large seeds with hard seedcoats. Scratch the surface of the seed with sandpaper or a nail file to damage its waterproof coating. Then soak overnight. Seeds which sink have absorbed water and are ready to sow, those which float should be scratched and soaked again. Speeds up germination by several weeks.

More detail on how to germinate individual varieties can be found by clicking on the variety in the Seed Shop

Light and air movement are essential to strong healthy growth. Too much warmth, too little light and overcrowding are sure recipes for failure. Be brutal and thin your seedlings. Far better to grow a few plants well, rather than many plants badly. You can increase your chances of success by sowing a few seeds at 2 or 3 week intervals to see when they will do best under your conditions.


Most seeds will keep for several years if kept cold and dry. Dry is the most important. Ideally your seeds should be kept in an airtight container with some silica gel to absorb any excess moisture. Keep the container in a cold room or fridge. Seeds can be taken out and replaced repeatedly as you use them. When the silica gel has absorbed all the moisture it can hold, the little blue beads inside it turn pink (hold it up to the light to see). Just put the silica in a warm place overnight to dry out, the beads turn blue and the silica gel is ready to use again.

Abbreviations on Seed Packets

HP – hardy perennial
BHP – borderline hardy perennial
TP – tender perennial
SLP – short-lived perennial
HA – hardy annual
TA – tender annual (sow spring)
Cl – climber
HB – hardy biennial
Bu – bulb
Tr – tree
Shr – shrub
# – needs cold to germinate

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