They are herbaceous perennials, generally with hairy serrated leaves and handsome flowers.
In perennials the stem shows a regular increase in thickness each year by the addition of a new ring of wood outside the old one - for details of structure see Plants: Anatomy.
The plants are hardy herbaceous perennials with narrow tufted radical leaves and an elongated stem bearing a handsome spike of white or yellow flowers.
The selection of suitable alpines, perennials and shrubs and trees also necessitates considerable knowledge on the part of the gardener.
Some deep-rooting perennials do not spread much at the surface, and only require refreshing from time to time by top-dressings.
Only a section of some of the best of the decorative hardy perennials can be noted, before we pass on to those popular subjects of this class which have been directly influenced by the hybridizer and improver.
High with pale blue flowers, are the best known perennials of the genus.
Ornamental strong-growing perennials requiring much space.
The perennials should be transplanted either every year or every second year.
Propagate perennials from root-slips and offsets.
Biennials and perennials should be sown before the middle of the month.
Sow annuals for succession in the last week, also biennials and perennials in the nursery compartment, for planting out next year.
Transplant strong plants of biennials and perennials to their final situations; also the select plants used for spring bedding.
Frequently, as in many Dicotyledons, the primary root, the original root of the seedling, persists throughout the life of the plant, forming, as often in biennials, a thickened tap-root, as in carrot, or in perennials, a much-branched root system.
Speciosum from Chile; it has tuberous roots, as have also such well-known perennials as T.