Perennial Plants

Perennials are plants that die down during the winter, but spring up and produce new stems annually. Some, such as Antirrhinums and Pansies, flower the first season, but usually they do not bloom till the second season. Many of the species improve with age, forming large clumps or bushes. The stock is increased by division of the roots, which, if judiciously done, improves the plant. Like annuals, they are divided into classes of hardy, half-hardy, and tender plants.

Hardy perennials do not require artificial heat to germinate the seeds, or at any period of their growth, and are the most easily cultivated of all plants. Seed can be sown from March to midsummer, transplanting in the autumn to their flowering positions; or it can be sown in August and September in a sheltered position to withstand the winter.

Half-hardy perennials require artificial heat to germinate their seed, and must be gradually introduced into the open. They can be sown during March and April in frames or a greenhouse, and many will flower in the first season. If sown between May and the end of August they will flower the following spring and summer. They require protection during winter, such as in a cold frame, or greenhouse. Tender perennials can be sown as directed above, but the plants should be kept constantly under glass.

Some perennials, such as Pinks, Carnations, Saxifrages, etc., do not die down, but retain their leaves. These are called evergreen perennials.

Plants: Biennials

Biennial plants take two years to flower, and then they die away altogether. In the first year of growth biennial plants display only their greenery. The seed of the hardy varieties is sown thinly outdoors any time between April and June, and the plants transferred in the autumn to the place where they are intended to flower. Seed is also sown in August and September for flowering the following year. The half-hardy kinds can be sown in May or June. These require protection during winter, such as in a greenhouse or cold frame.

Some biennial flowers are thought of as perennials because they are self-sowing which means they come back each year. Examples of biennial flowers are canterbury bells, hollyhocks, foxgloves, forget-me-nots, evening primrose and sweet william.

Text derived from: Gardening for the Millions by Alfred Pink