What Do Bumblebees Eat? Nectar, Pollen, and Buzz Pollination
What do bumblebees eat? Nectar and pollen, and nothing else. Nectar supplies sugar for flight energy, while pollen supplies the protein, fat, and amino acids a colony needs to raise its young. Every trip a worker makes to a flower patch is really two separate shopping runs happening at once: fuel for herself, groceries for the nest.
Nectar Fuels Flight, Pollen Builds Bodies
Nectar is mostly water, sucrose, glucose, and fructose. A bumblebee reaches it with a long, hairy tongue called a proboscis; tongue length varies by species, from short to long, letting different bumblebees work different flower shapes, with the longest-tongued species able to reach deep into tubular flowers that shorter-tongued bees skip. Collected nectar goes into a crop, an expandable pouch in the foregut sometimes called a honey stomach, where enzymes in the bee's saliva start converting sucrose into simpler sugars before she even gets back to the nest.
Pollen does different work. It carries the amino acids, lipids, and micronutrients larvae need to grow. Research on foraging preferences has found that bumble bees preferentially visit plants with pollen that has a higher protein-to-lipid ratio rather than foraging at random. Workers pack pollen into a smooth, concave patch on their hind legs called the corbicula, or pollen basket, moistening it with a bit of nectar so it sticks together for the flight home.
What Changes From Spring to Fall
A bumblebee colony's diet shifts as the season moves along, because the colony itself is a different size and shape at each stage.
Spring: One Queen, No Backup
A mated queen emerges from underground hibernation in early spring and forages alone until her first batch of workers hatches. She targets early bloomers like crocus, willow catkins, and dead-nettle, since a queen with no colony yet has no margin for a bad foraging day. Everything she gathers goes toward laying and warming her first eggs.
Summer: Full Colony, Maximum Demand
Once workers take over foraging, a colony can hold dozens to a few hundred bees, all needing pollen and nectar at once. Foragers spread across clover, lavender, comfrey, and various native wildflowers, with dozens of workers making repeated foraging trips every day to keep up with the colony's needs.
Fall: The Colony Shuts Down
New queens and males are produced late in the season, and after mating, the original colony ends. Newly mated queens are the only bumble bee survivors during the winter; the old queen and her workers die off as temperatures drop. The new queens feed heavily on late bloomers such as goldenrod and asters to build fat reserves, then burrow into loose soil or leaf litter to hibernate until spring.
How Bumblebees Choose Flowers
Bumblebees are not indiscriminate visitors. They key in on color (blue and purple stand out well against green foliage to a bee's eyes), on flower shape (bell- and tube-shaped blooms suit their tongue length), and on scent as a distance cue before they ever land.
Buzz Pollination
Some flowers, including tomatoes, don't produce nectar at all and only reward bees willing to work for pollen. The USDA Forest Service notes that bumblebees vibrate their wing muscles to shake pollen grains out of the anthers, a behavior called buzz pollination or sonication. Honeybees can't do this, which is one reason greenhouse tomato growers often stock bumblebee colonies instead.
Threats to Their Food Supply
Three pressures show up again and again in bumblebee research: shifting bloom times as the climate warms, which can leave queens emerging before their preferred flowers open; habitat loss from development, which removes the wildflower meadows and hedgerows colonies depend on; and pesticide exposure, which can impair foraging and navigation even at sublethal doses. Planting a season-long succession of native flowers, from early crocus to late goldenrod, is one of the few actions a home gardener can take that directly addresses all three.
Feeding Bumblebees in Your Garden
A garden that feeds bumblebees well needs blooms in every season, not just a summer burst. Crocus and willow for the queen in early spring, clover and lavender through summer for the working colony, and goldenrod or asters in fall for the next generation of queens covers the whole cycle. Avoiding pesticide use on flowering plants matters just as much as what you plant.
