Bumblebees are dependent on flowers for nectar (sugary liquid) and pollen (protein and minerals for developing larvae). They also need a place to shelter and build their nest to maintain a successful colony throughout its life-cycle.
There are a few tips to bear in mind when creating a bumblebee-friendly garden:
They need a continuous succession of flowers from spring to autumn, so there is always a food supply. Queens may appear even in January during warm spells; their disrupted hibernation making them hungry for nectar.
Most bumblebees prefer perennial flowers that flower from year-to-year. Herbs and traditional cottage-garden plants are ideal.
Flowers are best planted in large groups or patches (‘drifts’) of the same kind, so that the bees have good foraging sites. Bumblebees like to stick to one type of flower while foraging, and can waste energy scouting around for more forage.
A selection of flowers of different shapes (e,g bowl-shaped, bell-shaped, ‘lipped’ and tubular) will appeal to different species, as they have different tongue lengths.
If possible, a part of the garden should be left less intensively cultivated and more informal, to provide suitable nesting sites. Carder bumblebees will make their nest in long, tussocky grass. Bumblebees will also create nests in undisturbed compost heaps or underneath hedgerows.
You can also improvise by creating an underground nest site by digging a hole, putting a ball of moss or dry grass in the bottom and covering with a slab so as to leave a small entrance. Bumblebees will also use the smell of an abandoned, old rodent's or bird's nests as a cue to the presence of a suitable nesting site.
Flowering plants from these families particularly appeal to bumblebees:
Lamiaceae (Oregano, Lavender, Rosemary, Catmints, Deadnettle, etc). – mainly as a source of nectar. White deadnettle (Lamium album) is an essential early source of nectar.
Boraginaceae (Lungwort, Comfrey, Cynoglossum, Cerinthe, etc)
Scrophulariaceae (Foxgloves, Veronica, Hebe etc)
Dipsacaceae (Teasels, Scabiouses)
Asteraceae (Thistle-like flowers, Cardoon, Knapweeds, Asters, Solidago etc)
Fabaceae (Vetches, Clovers, Broom, Trefoils, Runner Beans etc). – mainly as a source of pollen. Red Clover (Trifolium pratense) and Birds foot Trefoil (Lotus corniculatus) are important bumblebee flowers.
Rosaceae (Single- flowered Roses, Brambles, Raspberries)
Ericaceae (Heathers, Blueberries, Bilberries, Strawberry Tree)
What bumblebees don't like:
Insecticides (including organic ones!)
Most bedding plants (i.e. as sold in polystyrene strips in garden centres and DIY stores): Petunias, Begonias, Busy Lizzies, French Marigolds, Pelargoniums, Pansies, etc, etc.
‘Double’ flowers (i.e. flowers where stamens are replaced by extra rows of petals)
Other highly-hybridized horticultural novelties.