RHS Garden Planning Choosing plants for the garden Perennials, annuals and bulbs Perennials Perennials are soft-stemmed plants that live for at least three years. They are used mainly to provide colour from mid- to late spring through summer (a few flower in autumn), but some have other specific uses. Many die back over winter, e.g. peonies (Paeonia), primulas and hostas. A few are evergreen or semi-evergreen, e.g. some hellebores (Helleborus) and bergenias. Perennials with good foliage While most perennials are grown for their flowers, many also have attractive leaves that provide a good foil for other flowering plants. A few perennials are grown more for their leaves than their flowers. Hosta Phormium Paeonia Rheum Late-flowering perennials These are valuable for providing colour in late summer to autumn. Aster Rudbeckia Helenium Sedum Perennials that attract bees and butterflies Plants with simple, open flowers are more attractive to pollinating insects than those with double flowers. Aster Liatris Sedum Coreopsis Monarda Solidago Echinacea Phlox Eupatorium Rudbeckia Perennials for ground cover Plants that form dense mats (not necessarily evergreen) are invaluable for covering large areas of ground and need little maintenance once established. Ajuga reptans Bergenia Hosta Alchemilla mollis Geranium Lamium maculatum Tender perennials Some perennials are not hardy but can be used to bring colour to a scheme from mid-summer onwards, as they are generally long-flowering. Most can also be used in containers. At the end of the season, either discard them, dig them up and overwinter in a greenhouse or take cuttings for use the following year. (Some may overwinter successfully outdoors if they are grown in well-drained soil in a sheltered position.) Agapanthus Pelargonium Verbena Felicia Penstemon Bulbs, corms and tubers
These are plants with a special mechanism that allows them to go dormant when conditions are unfavourable for growth. They are useful for giving bursts of colour at specific times of year. Many can be grown in containers. Late-summer and autumn-flowering bulbs are usually not hardy and have to be grown either in containers or against a warm wall. Early-flowering bulbs are good in drifts either in lawns, beneath deciduous trees or among deciduous shrubs and herbaceous perennials. Early-flowering bulbs snowdrops (Galanthus) crocus winter aconites (Eranthis) daffodils (Narcissus) Spring-flowering daffodils (Narcissus) tulips (Tulipa)
hyacinths (Hyacinthus) fritillaries (Fritillaria)
Summer-flowering Crocosmia Dahlia
Gladiolus Lilium (lilies)
Late-flowering Amaryllis Crinum
Annuals and biennials These are plants that complete their growth cycle within a 12-month period. Annuals usually germinate in spring then flower in summer; biennials are sown in summer, overwinter as small plants then flower the following spring. Uses • In bedding schemes to provide blocks of colour • To fill in gaps between other permanent plants that have yet to fill their allotted space • To experiment with colour schemes • In containers, window boxes and hanging baskets for seasonal display The colour wheel There are three primary colours: red, yellow and blue. Mixing any two colours together produces the complementary of the other colour. Hence: green (yellow + blue) is the complementary of red violet (blue + red) is the complementary of yellow orange (red + yellow) is the complementary of blue Complementary colours lie opposite each other on the colour wheel. They are always very exciting when combined together. Harmonising colours lie next to each other on the wheel and create a more soothing effect – e.g. green and yellow, orange and red.