Annuals are plants that complete their life cycle — i.e., germinate, flower, seed and die down – within 12 months.
Biennials require two seasons to complete their life cycle. They take approximately 12 months from sowing to flowering, after which they go to seed and die.
‘Hardy annuals’ (HA) are sown in the open in the spring, either in a nursery bed but more usually in the position where the plant is to flower in the summer. Some particularly hardy kinds can be sown outdoors in early autumn.
Half hardy annuals
‘Half-hardy annuals’ (HHA) require a longer growing season to develop and hence, in Britain, have to be sown in the protection of a green-house of cold frame or on a light window-ledge in mid-winter and transplanted to the open garden after all danger of frost has passed. ln some very mild gardens, where frost is nearly always absent, these plants can be sown in the open ground straight away.
F1 hybrid is a term applied to a seed strain obtained by crossing two pure bred selections or varieties, which are close relatives. The resulting plants are usually superior to and more vigorous than their parents, but seeds from them do not breed true.