Biennials are herbaceous plants that complete their life-cycle in two years. Growing in the first year and flowering in the next. Some plants grown as biennials are actually short-lived perennials, they tend to be dug up after flowering because they do not perform well in their second year.
Care: Like Hardy Annuals, Biennials can stand the cold so seeds are sown outdoors in Spring to flower the following Summer and it is important that the soil is not too rich or it will encourage leafy growth instead of lots of flowers.
It is possible to buy two year old plants during Spring which flower that Summer. Clear the ground of all weeds and keep them well watered. Add plenty of well-rotted organic matter when planting and stake tall plants. Deadheading regularly throughout the growing season will encourage more flowers although you may want to leave some flowers to allow them self-seed around the garden and save you some work. In autumn, after flowering and once the plants begin to die down pull them up and put on the compost heap.