Best started off indoors on a warm, sunny windowsill, lavender seeds can be sown anytime from the beginning of February right up until the end of June. Using either a seed tray – or more ideally a plug tray – fill to the top with a good quality multi-purpose seed compost then tap it down firmly to get rid of any large air pockets. Sow the lavender seed directly onto the surface of the compost then cover with either glass or clear plastic to help preserve humidity. After 20 - 50 days the new seedlings should begin to emerge, at which point remove the glass or clear plastic cover at the first sign of growth otherwise fungal infections can take hold.
Pot the seedlings on individually when they are large enough to handle in to 3 inch pots containing a good quality compost such as John Innes ‘Seed and Potting’. These can now be grown on for a few more weeks in a cooler but not cold position. Gradually accustom the plants to outside conditions before planting outside permanently when the threat of frost is over. If you are using the lavender for edging or hedging plant out into their permanent position no more than 1 ft apart.
In order to maintain the shape of your plants they must be trimmed back immediately after flowering so that new growth is encouraged before the onset of winter.