Bishy Barnabee’s Cottage Garden
Biennial Flower Seeds
Patient flowers, second-year rewards
Growing biennial flowers — your questions answered
What is a biennial?
A biennial completes its life cycle over two years. You sow the seed in year one, the plant grows leaves and roots through summer and autumn, overwinters in the ground or in pots, then flowers, sets seed, and dies in year two. Foxgloves, sweet williams, honesty, and wallflowers are all classic biennials.
When should I sow biennial seeds?
The sweet spot for sowing biennials is late spring to mid-summer — from May through July. This gives the plants enough time to develop strong roots and leafy growth before winter, which is what triggers their flowering response the following year. Sown too late, they may not have enough time to establish.
Will biennials self-seed?
Many will, beautifully. Foxgloves, honesty, sweet rocket, and forget-me-nots are particularly generous self-seeders. If you leave a few seed heads on the plant in their second summer, you will often have a self-sustaining patch that renews itself year after year — the essence of a cottage garden.
Do biennials need protection over winter?
Most hardy biennials are tough enough to overwinter outside in UK gardens without special protection, especially once they are well-rooted. Young seedlings raised in modules benefit from a cold frame or unheated greenhouse through the worst of the winter, particularly in colder regions or exposed sites.