Bumble Bees are Important Pollinators

by Jason Graves

Early spring is a good time to bring awareness to the lifecycle of bumble bees. Bumble bees are a 'keystone' species. Large numbers of other species in our Kansas ecosystems depend on them. These magnificent pollinators are at the center of a thriving ecosystem and our native plants rely on them to reproduce. Bumble bees are also critical pollinators of vegetables and fruits.

Buzz pollination

Bumble bees are quite the efficient pollinators. In fact, the way in which bumble bees pollinate is in part due to the ‘buzz’ they make as they move from flower to flower. ‘Buzz’ pollination is quite interesting. The bumble bee actually grabs the pollen producing structure of the flower in its jaws as it vibrates its wing muscles. This creates vibrations that dislodge pollen from the flower and results in pollination.

Bumble bees are the only pollinators used for certain greenhouse crops and are also active in cooler temperatures and for longer lengths of time compared to honey bees due to their larger bodies. These bees are each capable of pollinating a single flower, while it may take up to 7 honey bees to accomplish the same effect.

Bumble bee habitat

Bumble bees are suffering significant declines in population due to loss of habitat and so the creation of new habitat is an important part of ensuring the benefit of bumble bees is not diminished even further. Here are three simple things you can do to enhance bumble bee survival in your landscape.

Provide flowers early and late

Of course, flowers are a key ingredient for any pollinator habitat. Bumble bees need flowers from which to gather pollen and nectar. They utilize pollen and nectar for survival and reproduction and a diverse group of flowers is key to bumble bee habitat success. It is particularly important to provide blooms both early and late in the season during times when food is scarce.

The bumble bee life cycle is important to understand. Only the queen bumble bee overwinters. The entire colony dies in the fall and the queen must be well fed and find a protected place to survive the winter while she waits for spring to arrive.

Late season flowers are critical for allowing the new bumble bee queen to build up her fat stores for overwintering and early season flowers are critical to her ability to nourish a new colony. In spring, the overwintering queen must not only feed herself, but collect enough pollen and nectar to nourish the first batch of developing offspring. This requires flowers.

A few good early spring plants for central Kansas include: American plum (Prunus americana), redbud, chokeberry, golden current, fruit trees, Jacob's ladder, wild geranium, violets, bluestar (Amsonia), bluebells (Mertensia), prairie smoke, golden alexander, baptisia (false or wild indigo), spiderwort, penstemon, and early figwort.

Goldenrod, aster, sneezeweed (Helenium autumnale) and sunflowers can provide a good source of nectar and pollen in the late fall for bumblebees.

Provide nesting and overwintering sites

Bumble bees generally nest underground, often in abandoned holes made by squirrels or other rodents. Some species also nest in cavities such as hollow logs, dead trees, under rocks, an unused birdhouse, or even under a compost pile. By maintaining at least a few natural , undisturbed areas for bumble bee nesting in your landscape you will support healthy bumble bee colonies.

Bumble bee queens need access to small cavities just below or even on the ground surface. They utilize things such as leaf litter and loose soil, and are also known to overwinter in wood piles, rock walls, and walls in sheds. Ornamental grasses left standing for winter also make great bee overwintering sites. Overwintering sites near a flower bed are also the best since the queen needs close access to food while beginning the new nest in spring.

Avoid Pesticides

Finally, any pollinator friendly landscape should avoid the use of pesticides. In the event that an application must be made, be sure to do it when bees are not active (after dark) and avoid using broad-spectrum insecticides which are highly toxic to bees.