The first step is to determine the impression and atmosphere to be created, and whether it is an annual, perennial or naturalising planting scheme. Selection is also strongly determined by factors like:
- soil type
- site conditions (exposure to light)
Tulips, hyacinths, narcissi and well-known flower bulbs like the crocus and grape hyacinth are particularly suitable for single-year planting schemes. As for perennials, the suitability of different bulb varieties has been established during two test periods and in a number of climate zones.
Soil conditions, water economy and incident light are particularly important where perennial or naturalising planting schemes are concerned. Flower bulbs for naturalising are best suited to locations that closely reflect the natural habitat of the plants. This results in natural-looking planting that adds freshness to what can be a dark, woodland type of environment.
Allium ursinum (ramsons), Anemone nemorosa (wood anemone), Anemone ranunculoides (spring anemone), Arum italicum (Italian arum), Colchicum, Convallaria majalis, Corydalis cava (holewort), Corydalis solida, Cyclamen, Eranthis, Galanthus (snowdrop), Hyacinthoides non-scripta (wild hyacinth), Ornithogalum.
For ponds and wet areas:
Fritillaria meleagris, Arum italicum, Leucojum, Camassia.
For verges and lawns:
Crocus, Chionodoxa, Galanthus, Scilla and early flowering narcissi.
Flower bulbs can be used in a variety of ways, depending on the ultimate aim.
- As annuals: annual planting is generally chosen in cases where bulbs are supposed to create a mass colour effect: flowerbeds with successive flowering of crocuses and tulips, seas of grape hyacinth or extended ribbons of large trumpet narcissi. Flower bulbs with strong colours (red, yellow, blue) are particularly suitable for this purpose.
- As perennials: perennial planting means that the planted spring bulbs remain in the ground and are allowed time to die back and ready themselves underground for the following growing season. Spring bulbs used this way therefore follow the same cycle as other perennial plants, and they frequently form part of existing perennial planting schemes like plant, shrub or rose borders. Spring bulbs suitable for use as perennials include certain narcissi, tulips and hyacinth cultivars and other less common species. In this situation it is essential that the flower colours of the different bulbs harmonise with each other as well as with the colour scheme of other fixed planting.
- Bulbs suitable for naturalisation offer just a little bit more than those classified as perennials. Naturalising bulbs also remain in the ground and come into flower every year, but they have the additional advantage that, if the air and light conditions are right, they will spread and increase. Naturalising bulbs can be used alone – think of snowdrops and crocuses in lawns and grass verges - but they can also be included in existing planting schemes, for example combined with ground cover under trees and shrubs. Bright colours are not recommended in such naturalistic settings, and preference should be given to muted shades like soft yellow, pastel blue or white. Narcissi, Scilla and Leucojum are examples of naturalising bulbs that will definitely come into their own here.