Despite the bitter winds and rain showers, the recent sunshine has awoken the bumblebees. They’re everywhere, zipping around our plot, searching out pollen and nectar. Narratives about declining bee populations focus almost exclusively on honey bees, while Bumblebees seem quite neglected. Perhaps the development of bee keeping on an industrial scale and the potential for industrial-scale financial losses when colonies collapse is at the root of this preoccupation. Bumblebees are the most significant pollinators in the Northern hemisphere for field beans, fruit and tomatoes; however, according to research by Dave Goulson, there has been a serious decline in Bumblebeess and 13 species became extinct between 1950 and 2000.
Frequent Bumblebee nesting sites include holes in the ground, tussocky grass, bird boxes and under garden sheds. Their nests are quite small and don’t create a store of honey, hence are more sensitive to the availability of pollen and nectar-rich flowers. We can provide early flowers on our plots to help bumblebee Queens survive when they emerge in the early spring weather, when sources of pollen and nectar are often scarce. Without that early source of food, they can die.
The key is to have a succession of accessible bee-friendly plants that are rich in pollen and nectar flowering from early spring through to late summer. The greater the number of suitable flowering plants the better, with at least two bee-friendly plants for each flowering period, while the next wave of flowers are in bud, ready to take over. Highly bred cultivars with double flowers are not ideal as many have had the nectar and pollen content bred out, the plants are often sterile and therefore useless to pollinators; when they do produce pollen or nectar, the complicated petal structures are also difficult for insects to negotiate. Stick to flowers with simple structures, local wild flower selections often being the best choice, while annuals such as Nigella, Calendula and Limanthes douglassii (poached egg plant) are prolific self-seeders, ensuring there will be flowers next year without your labour.
Crucial times in the Bumblebee lifecycle:
- When queens emerge from hibernation in early spring, having spent the whole winter underground where they will have survived, for up to six months, on stored body fat. They need access to nectar to quickly rebuild their energy reserves, before they fly off in search of a suitable nest site.
- When establishing their nests in early spring, the queens collect pollen, which they mix with wax they secrete to form a mound in which to lay their 1st brood of eggs.
- While they incubate the eggs for several days, the queens survive on nectar stored in a pot-like structure they create in front of their nest mound.
- When the eggs hatch into larvae, they are fed on pollen and nectar; after 2 weeks of feeding the larvae spin cocoons before they develop into adults.
- In late summer, when the queens fatten up ready for hibernation.
With few other flowers available, hedgerow trees and shrubs, such as willows, wild cherry, hawthorn and blackthorn, are important food sources for emerging bumblebee queens in spring. Beneath the tree and shrub layer, key plant species include dead-nettles, knapweed and foxglove, phacelia and crimson clover. Winter flowering honeysuckle, early hellebores, pulmonaria and native primroses are good early food plants with alliums and English bluebells following on. Plants such as red clover, yellow rattle and bird’s-foot-trefoil are good pollen sources for queen and new worker bumblebees, while knapweed and scabious provide nectar.
In planning your bee-friendly garden or plot, about now (mid-spring) is a good time to plant out winter aconites and snowdrops for next year as they establish more strongly when planted ‘in the green ’, meaning in full leaf, after flowering. But, do ensure your plants are not wild gathered but from reputable cultivated stock. I’ve just planted out clumps of snowdrops ‘in the green’ to establish for next spring, and am mapping out what’s flowering where and when across our plot so I can ensure we’re providing successional pollen and nectar sources.
We have clumps of white and purple comfrey in the hedges, which began flowering in late February, along with primroses, daffodils and crocus. Daffodils are not a favourite with Bumblebees, which only seem to visit them as a last resort. Cuttings of winter flowering honeysuckle from our last garden are now scattered around the plot and in the hedges, and we noticed early bees visiting the flowers during warm late winter and early spring days. The Hellebores are still all in flower, along with the primroses beneath the hedges, while the flowering currants (Ribes sanguineum) are covered in flowerbuds opening into pink cascades, and wreaths of blackthorn blossom ripple up the hillside where the young hedging whips were planted last autumn.
We should give as much thought to the flowers we plant as we do to our food crops, planning successional flowering to sustain a healthy population of pollinating insects. Our plots and food crops will benefit from the resulting increase in beneficial insects.
Some useful websites: