Milkweed blooms and the bees they sustain

The air carries a sweet weight near Westminster's open spaces, where clusters of pink and orange flowers rise from the grassland. Showy milkweed stands tall with broad leaves and dome-shaped flower heads, each bloom a dusty rose color. Nearby, butterfly milkweed spreads lower to the ground, its flowers burning bright orange in the summer heat. Both plants have opened their complex flowers just as the Golden Northern Bumble Bee reaches peak activity in its breeding season.

The Golden Northern Bumble Bee works these milkweed flowers with deliberate intensity. She lands heavily on a flower cluster, her golden-yellow body contrasting with the pink petals of showy milkweed. Each milkweed flower presents a challenge. The pollen sits trapped in small sacs that must be triggered to release their contents. The bee grips the flower and vibrates her flight muscles without flying, a behavior called buzz pollination. The vibration shakes loose the pollen packets, which attach to her legs and body as waxy yellow masses. She moves methodically from flower to flower, collecting both nectar and pollen while inadvertently transferring genetic material between plants.

This relationship sustains both species through summer's demands. The Golden Northern Bumble Bee, threatened throughout its range, depends on diverse flower resources to feed her growing colony. Queen bees emerged from winter hibernation in spring and have spent weeks establishing underground nests. Now their worker daughters forage constantly to support developing larvae back in the colony. Milkweed provides high-quality protein from its pollen and concentrated sugars from its nectar. The timing aligns perfectly with the colony's peak growth period, when dozens of workers need fuel for constant foraging trips. For the milkweeds, these bees serve as essential pollinators. The plants' complex flower structure evolved specifically to ensure that visiting insects pick up and transfer pollen effectively. Without pollinators like bumble bees, milkweed populations cannot produce the seeds that will become next year's plants. Each successful pollination leads to the formation of the distinctive pointed pods that will split open in autumn, releasing seeds on silky white plumes.

Other native bees and butterflies also visit these blooming milkweeds, but the Golden Northern Bumble Bee's size and strength make it particularly effective at working the flowers' intricate mechanisms. Two-tailed Swallowtails and Orange Sulphurs flutter between the orange butterfly milkweed blooms, their long tongues reaching deep for nectar. The invasive Western Honey Bee also forages here, though it often steals nectar by biting holes in flower bases rather than entering through the proper channels that ensure pollination. The native bees remain the more reliable partners in this ancient exchange between plant and pollinator. Walk quietly among these flowering patches and you can hear the steady hum of working bees, their flight muscles generating the vibrations that unlock each flower's hidden rewards.