Start sowing biennials such as Icelandic poppies (papaver nudicaule) , sweet rocket (hesperis matronalis). foxgloves (digitalis), honesty (lunaria annua), sweet william (dianthus barbatus) and wallflowers (erysimum cheiri) which naturally shed seed this time of year.
Fill seed pots or trays with peat free growing medium, water and then sow the seeds thinly over the surface before covering with fine layer of compost. Leave outdoors in the sun but keep well watered. Once the seedlings have emerged move out of scorching sunlight and when big enough with true leaves transplant and grow on in individual pots. In the autumn plant them in their final positions to flower early next summer.