Perennials and biennials

This covers the vast majority of wild flowers. The main point to appreciate here is that they should not be sown into the garden where they are required to flower. This is because unless you are very skilled you will not be able to distinguish the wild flower seedlings from weeds and the growth rate of perennial species tends to be slow in the seedling stage and they are liable to be engulfed by fast-growing annual weed species. The approach to growing them is exactly the same as one would adopt for perennial herbaceous border plants and they should be propagated in clean compost before transplanting into their final flowering positions. Some wild flower species are strictly spring germinators and others will germinate in autumn or spring.

General recommendation for sowing perennials and biennials

From late June to September with prior scarification if recommended, sow seed shallowly into trays of clean seed compost. Place outside (against north side of a wall or fence so that trays are shaded and can be kept watered with minimum effort when sun strength increases in spring).

A wooden framework around the trays covered with fine mesh wire will exclude rodents which might find seeds and young seedlings appetising. Many species will germinate almost immediately and can be pricked out into pots prior to transplanting into flowering position in late autumn or the following spring, ideally the former.

Species not germinating should be held outside over winter and retained until mid May. Take care that the boxes are not allowed to dry out. Watering should only be necessary to any degree in early autumn and late spring. Most species needing cold exposure will germinate late March/April. Species definitely known to require stratification i.e. spring germinators can with advantage be sown outside up to the end of January whilst a spell of cold weather can still be expected.