Mason bees are solitary pollinators that use pre-existing holes to lay their eggs. Providing a specialized house is the easiest way to attract them to your garden, as they do not sting aggressively. Successful attraction depends almost entirely on selecting the right physical location for their nesting site. A properly placed house provides a safe, warm, and convenient environment, encouraging female bees to fill the nesting tunnels.
Optimal Sun Exposure and Height
The success of a mason bee house hinges on its exposure to morning sunlight, which provides the necessary warmth for the bees to begin their daily activity. Mason bees are ectotherms, meaning they rely on external sources to regulate their body temperature, which must reach over 90°F for flight. Therefore, the house should ideally face Southeast or East to receive the first rays of the sun, giving the bees an early start to foraging.
Morning warmth encourages bees to leave the nest and forage earlier than those in shaded locations. The house should be mounted firmly to a stable structure, such as a fence or shed, to prevent swinging or vibration that may disturb the developing larvae. A mounting height of four to seven feet off the ground is recommended, which is convenient for observation and above the reach of ground pests.
For protection from rain and moisture, the house should be tilted slightly downward (five to ten degrees). This angle ensures that any water blowing into the nesting tunnels drains immediately. In regions with intense summer heat, a location that receives afternoon shade is preferred to prevent the midday sun from overheating the house and harming the bee larvae inside.
Proximity to Nesting Materials
The nesting site must provide the two primary resources mason bees require: pollen/nectar for food and mud for construction. Female mason bees are not long-distance fliers, typically limiting their foraging to an area within 300 to 500 feet of the house. Therefore, the house must be situated close to early-blooming plants like fruit trees, berries, or spring flowers that serve as their food source.
The mud is used to build the protective cell walls and the final plug for the nesting tunnel. Mason bees require a heavy, clay-rich soil that they can mold into a strong, durable barrier. They will not use sandy or loose dirt, as it crumbles when dry, leaving the developing bees vulnerable to pests and predators.
The mud source should be located within 10 to 50 feet of the bee house. If your natural soil is not clay-heavy, you can create a dedicated source by mixing clay soil or commercial mud mix with water and keeping it damp during the nesting season. Placing this mud source slightly away from the house ensures the weak-flying bees, particularly when they first emerge, do not fall directly into the wet material.
Protecting the House from Weather and Pests
Protecting the mason bee house from the elements and predators is important. A deep roof overhang, shed eave, or tree canopy provides shelter from direct, wind-driven rain. Keeping the nesting tunnels dry prevents persistent moisture, which promotes the growth of mold and mildew detrimental to the developing cocoons.
Woodpeckers pose a common threat. A simple deterrent is to secure a piece of hardware cloth or sturdy wire mesh a few inches in front of the house’s entrance. This barrier prevents the bird from gaining enough leverage to peck out the nesting material while still allowing the bees easy access.
Other threats include parasitic wasps, which lay their eggs inside the mason bee cocoons, and pollen mites that consume the food supply. The best defense against these internal pests is using openable or replaceable nesting materials, such as cardboard tubes or grooved wooden trays. These materials allow for the annual harvesting and cleaning of the cocoons. Removing the filled nesting material and storing it securely after the nesting season ends also protects the larvae from late-season pest activity.