Naturalising bulbs survive the winter under the ground, just like perennial plants. This means they can simply remain undisturbed in the soil after they flower. But for the success of next year’s flowers, the foliage of naturalising bulbs has to be given the time to die back completely. This gives the bulb a chance to store enough reserve nutrients for a profuse flowering display next year. For this reason, an expanse of grass that contains naturalising bulbs should not be mown until the leaves produced by the bulbs are completely desiccated.
Many naturalising bulbs will extend the flowering season by blooming early in the year. They naturalise (increase in number) by producing seed or small bulbs, corms or tubers. Some species such as Anemone nemerosa (Wood Anemone), Eranthis hyemalis (Winter Aconite), Galanthus nivalis (Snowdrop) and Hyacinthoides non-scripta (Bluebell) will even become dense carpets of plants.
Their many uses
The early-flowering varieties will ensure colour beneath deciduous trees and shrubs when their branches are still bare. Naturalising bulbs will provide an even better effect when planted in groups or combined with others. Since they can remain undisturbed, they make a good choice for planting with perennials, roses or shrubs. They will also thrive in grass – in parks or verges, for example.
Many varieties of flower bulbs are suitable for naturalising in public green spaces. They vary in colour, shape, height and flowering period. Since many of them produce large quantities of nectar, these varieties will also attract bees and butterflies. The following flower bulbs are examples of excellent naturalisers for public green spaces.
- Allium sphaerocephalon – Round-headed Garlic, Drumsticks
- Allium ‘Purple Sensation’ – one of the ornamental onions
- Allium ursinum – Ramsons
- Anemone blanda – Grecian Windflower
- Anemone nemerosa – Wood Anemone
- Camassia esculenta – Indian Hyacinth, Camas, Wild Hyacinth
- Chionodoxa lucilaea – Glory-of-the-Snow
- Chionodoxa sardensis – Lesser Glory-of-the-Snow
- Colchicum – Autumn Crocus, Meadow Saffron
- Corydalis solida – Fumewort
- Crocus tommasinianus – Early Crocus
- Crocus vernus – Spring Crocus, Giant Crocus
- Eranthis hyemalis – Winter Aconite
- Fritillaria meleagris – Chequered Fritillary, Snake’s Head Fritillary
- Galanthus nivalis – Snowdrop
- Hyacinthoides non-scripta – Bluebell
- Leucojum aestivum – Summer Snowflake
- Muscari armeniacum – Grape Hyacinth
- Narcissus poeticus recurvus – Poet’s Daffodil
- Narcissus pseudonarcissus – Wild Daffodil, Lent Lily
- Ornithogalum nutans – Nodding Star-of-Bethlehem
- Oritogalum umbellatum – Star-of-Bethlehem
- Puschkinia libanotica – Striped Squill
- Scilla bifolia – Alpine Squill
- Scilla siberica – Siberian Squill
- Tulipa sylvestris – Woodland Tulip
Most naturalising bulbs will thrive in full sun or semi-shade. Some prefer a location with moist soil, others a drier place. To get an idea of how many bulbs are needed to obtain a uniform planting that will create a dense flowering display in the first year, you would need 100 bulbs/m2 for the Woodland Tulip and 150/m2 for snowdrops. Smaller quantities would be sufficient for a less dense flowering display or when combining these bulbs with other plants. Flower bulb suppliers specialise in providing this kind of advice.