Life Cycle of Plants

 
 

Life cycle of higher plants

  1. Perennial

    • Survive year after year

    • In wild, found in relatively stable environments

    • Most flower each year

  2. Woody perennials (trees or shrubs)

    • secondary growth: xylem tissue of dead ‘lignified’ cells (deposited lignin)

    • lignification’ gives strong, rigid structure

    • lignin also resists infection, rot and decay

    • Some gymnosperms are very large (Sequoiadendron giganteum), and very long-lived e.g. Taxus baccata 3000 years

    • deciduous or evergreen woody perennials

  3. Herbaceous perennials

    • do not develop genuine woody tissues

    • in seasonal environments above-ground parts (stems, leaves and flowers) often die back

    • cold winter or hot, dry summer spent as tubers, bulbs, corms, rhizomes

    • ‘deciduous herbaceous perennials’ e.g. Aconitum napellus (monkshood), Iris pseudacorus (yellow flag)

    • ‘evergreen herbaceous perennials’ e.g. Primula vulgaris (primrose), Bergenia purpurascens (elephant’s ears) - retain green foliage throughout year

  4. Biennial plants

    • live for two years

    • build up nutrients to flower after two growing seasons

    • after flowering, die at end of year 2

    • e.g. Daucus carota (wild carrot) spends one winter as root tuber; Digitalis purpurea (foxglove)

  5. Annual plants

    • complete life cycle in one year

    • can thrive in short-lived habitats

    • invariably herbaceous

    • e.g. Helianthos annuus (sunflower); Alyssum ‘Snowdrift’

  6. Ephemeral plants

    • ultimate opportunists

    • complete entire life cycle in months or weeks

    • major weeds

    • e.g. Senecio vulgaris (groundsel)

    • e.g. plants in harsh desert germinating after rains

horticultural life-cycle definitions

  1. Many perennial plants used as horticultural biennials or annuals

  2. Crops or seasonal displays e.g. Viola x wittrockiana (pansies) (perennial treated as annual); Begonia x semperflorens (cannot survive north European winter), Erysimum cheiri (wallflower) (perennial treated as biennial - straggly growth after several years)

  3. Horticultural perennials

    • non-woody plants that flower each year, bringing colour to garden

    • some short-lived, some long-lived

    • ‘herbaceous perennials’ - refers to plants that die back over winter (e.g. Hostas)

    • ‘perennials’ - retain leaves over winter, but non-woody (e.g. Bergenia)

    • not all botanical perennials are horticultural perennials! (e.g. wallflower)