Most native bees raise their young beneath your feet

Around 70% of North America's native bee species nest underground. That scruffy patch of exposed soil isn't necessarily a gap in the garden. It can be the garden's nursery. Mining bees, squash bees, polyester bees and many sweat bees all belong to this largely hidden population. Their entrances may look like tiny anthills, with loose soil piled around a hole. And a busy cluster doesn't necessarily lead to one enormous nest. Most ground-nesting bees are solitary: the neighbors have gathered in suitable habitat, but each female makes her own nest. Close together doesn't mean working together.

For a solitary mining bee, motherhood means doing the excavation and the grocery shopping herself. She digs a tunnel with branches leading to individual chambers called brood cells. Then she visits flowers, collects pollen and mixes it with nectar to make a food supply. She lays an egg with that provision, seals the chamber and starts another. There's no need for the newly hatched larva to find a flower or follow its mother outside. Its food is already beside it. Each sealed room contains both a developing bee and the meal that will support its growth.

Underground rooms also need protection from water. Some ground-nesting bees line their brood cells with a waterproof film. Cellophane bees get their name from a lining that resembles clear plastic when it dries. Other bees leave a more visible signature: chimney bees pile excavated soil into little turrets above their entrances. The architecture varies, too. Some nests have branching passages, while others have brood cells connected to a main tunnel. These aren't simply holes where adults hide between flower visits. They're constructed spaces where eggs hatch, larvae feed and pupae develop before adult bees emerge.

The activity above ground can end long before the nest is empty. In spring-active mining bees, the mother dies after her weeks of gathering food and stocking chambers. Rain can wash away the little soil mounds, leaving no obvious sign of the nursery below. Her offspring remain underground, with the next generation emerging the following spring. Ground-nesting bees pass through egg, larval, pupal and adult stages, and the stage in which they overwinter varies. So a nesting patch that looks deserted may still be occupied. The disappearance of flying adults isn't the end of the story. It's the part where most of it moves out of sight.

That changes what helping bees looks like. Flowers supply food, but accessible soil supplies nesting space. Sunny, well-drained patches with sparse vegetation can provide both a place to dig and nearby plants to forage on. Thick mulch, plastic coverings and paving can block that access; digging or tilling an occupied patch can destroy the nests themselves. Even small areas of exposed soil can offer nesting opportunities in a yard. You don't have to fill every gap with another plant. Sometimes the useful thing is to leave a patch open, leave it undisturbed and let the next generation finish growing beneath it.