Mason bees are among the most effective pollinators you can attract to a home garden. A single female mason bee visits up to 2,000 flowers a day — roughly 100 times more productive per flower visit than a honey bee. They are gentle (stingless for practical purposes), native across North America, and will move into purpose-built houses with minimal encouragement if conditions are right. Here is everything needed to set up and maintain a mason bee house effectively.
About Mason Bees
Mason bees (genus Osmia) use mud to seal nest cells — hence the name. The blue orchard mason bee (Osmia lignaria) is the most common North American garden species, emerging in early spring weeks before honey bees are active. Each female provisions hollow tubes with pollen-nectar balls, lays eggs, seals cells with mud, then dies. Larvae overwinter as adults and emerge the following spring.
Choosing the Right House
Mason bees prefer tubes of 5/16 inch (8mm) internal diameter — sized for Osmia lignaria specifically. Tubes should be at least 6 inches (150mm) deep to allow enough space for multiple cells per tube. Paper or cardboard insert tubes that can be removed and replaced are far superior to fixed wooden tubes or drilled blocks, which cannot be cleaned without destroying the nest. Avoid decorative bee houses with a mix of material types (mesh, pinecones, bark) — mason bees use only tubes of appropriate diameter and ignore the rest. A simple, functional design with 50 to 100 paper insert tubes is the starting point. For a broader overview of bee habitat structures, see our guide to choosing and installing a bee hotel.
Siting and Mud
Face the house east or south-east for morning sun. Mount at eye height — 5 to 6 feet — with a firm, non-wobbling attachment. Mason bees need mud to seal nest cells; a patch of damp bare clay soil within 50 feet is ideal. Do not use potting mix — the texture is wrong. A shallow water dish with pebbles nearby supports foraging activity.
Seasonal Care Schedule
Spring: Install the house with fresh tubes before daytime temperatures reliably reach 50°F (10°C). Set out any overwintered cocoons at this point. Early summer: Leave the house completely undisturbed while females are actively nesting. Late summer: Once no females are entering tubes and new tubes remain unsealed for two weeks, remove paper inserts and store them in a breathable paper bag in an unheated shed at 35 to 50°F (2 to 10°C) through winter. The following spring, return tubes to the house and add fresh empty ones. For general pollinator planting to support mason bees, see our article on attracting bees to your garden.
Frequently Asked Questions
- Do mason bees sting?
- Female mason bees can sting but are extremely reluctant to do so and will not sting unless directly handled and squeezed. They do not defend a colony territory as honey bees do, making them safe to have near children and pets.
- Can I buy mason bee cocoons to get started?
- Yes. Mason bee cocoons are available from specialist suppliers in late winter and early spring. Purchase from a regional supplier if possible, as locally adapted bees are more likely to thrive in your climate.
- How many nesting tubes do I need?
- Start with 50 to 100 tubes. A single female fills 4 to 6 tubes per season. A small starting population of 10 to 15 females can grow to fill a full house within two to three seasons.
- What do mason bees eat?
- Pollen and nectar from flowering plants. They are generalist foragers and will use a wide range of spring-blooming plants, including fruit trees, willows, dandelions, and native wildflowers.