Annuals, ask a botanist and he or she will probably tell you that an annual is a plant whose seed germinates and which develops, flowers, produces its own seed and then dies all in one year; he may say it all takes place over a 'course of seasons'.
So most annuals germinate in the spring, flower in late spring and summer and die in the late summer or autumn; alyssum, clarkia and zinnia are familiar examples. A few, however, can also behave as winter annuals, germinating in the late summer and autumn then remaining partially dormant over the winter before starting into growth again in spring and completing their cycle in summer. Annual chrysanthemums from the Mediterranean fall into this group.
Now the situation becomes rather less clear. For many of the plants which we grow in gardens as annuals, plants like petunias and salvias, are not truly annuals at all. Usually these are shrubs or perennials from warm climates which, once they germinate in spring, develop so quickly that they flower well in their first summer. In many areas, they're not sufficiently tough to survive the autumn frosts so are quickly wiped out; in warmer regions they may survive the winter but perform much less impressively the following year.
Both these groups, true annuals and plants which can be grown as annuals, are included in this book along with a third smaller group of short-lived plants, the biennials. Like annuals, biennials usually pass through their entire life cycle in one 'course of seasons' but their growth is always spread across two years. So their seed germinates in summer, established plants overwinter then flower in spring.
Now, at the risk of adding further confusion, it must be admitted that many of the plants we grow as biennials are, in their natural habitats, perennials or shrubs! However, when sown in summer plants like wallflowers and double daisies have the capacity to flower so prolifically in their first spring that we naturally take advantage.
Finally (yes, finally) a few biennials, like some foxgloves and sweet Williams, have been so transformed by plant breeders that when sown in late winter or early spring they flower in their first summer - as annuals! This only applies to certain specific varieties, and frankly, turning some of our relatively few spring flowering bedding plants into summer flowers (of which we already have so many) hardly seems progress.