Carpenter bees are highly effective pollinators in many garden ecosystems. These large, solitary insects are often mistaken for bumblebees but lack the dense hair covering on their lower bodies. Unlike social species, female carpenter bees bore individual tunnels in wood to create nests for their young. Attracting these insects involves strategically providing consistent food sources and appropriate nesting materials to encourage a stable population for pollination.
Cultivating Preferred Floral Resources
Carpenter bees are generalist foragers, but their large size and powerful musculature influence their specific flower preferences. They are especially drawn to large, open blooms that provide easily accessible pollen and nectar. Examples of attractive plants include sunflowers, hollyhocks, zinnias, and various fruit tree blossoms, which offer abundant rewards during the foraging season.
The bees also exhibit “nectar robbing” on deep, tubular flowers like salvias or penstemens, which their large bodies cannot easily enter. They use their mouthparts to cut a slit near the base of the flower to access the nectar, often bypassing the reproductive structures. Although this action does not result in pollination, the bees still collect pollen from other sources, making them valuable pollinators for a wide variety of crops.
Providing a continuous bloom cycle is important for supporting the bees from their spring emergence through late summer when the new generation appears. Planting staggered blooms from early spring species like borage or early legumes to later-season flowers ensures a reliable supply of energy. This consistent food source encourages the female bees to remain in the area while they provision their nests with a mixture of pollen and nectar.
Establishing Suitable Nesting Materials
Providing alternative, untreated wood sources is essential to discourage females from utilizing human structures for nesting. They strongly prefer softwoods that are unpainted, weathered, or unstained, such as:
- Pine
- Cedar
- Redwood
- Cypress
To offer an appealing site, set up wooden blocks or posts that are at least 3/4 inch thick in a sunny, sheltered location. A highly effective method is to drill holes approximately 1/2 inch in diameter and 3 to 6 inches deep into the wood grain. The female will often utilize these pre-drilled holes, which saves her the energy of excavating the initial entrance.
Placement is important, as the bees seek areas protected from heavy rain and wind, such as under eaves or deck railings. Carpenter bees are attracted to the scent of previous nesting activity. Placing new nesting blocks near existing, non-structural wood where activity has been observed can significantly increase the chances of colonization.
General Habitat Maintenance for Encouragement
Maintaining a welcoming environment requires management that ensures the bees’ well-being. The complete avoidance of broad-spectrum insecticides and pesticides in the garden area is important. These chemicals can contaminate the pollen and nectar the bees collect, directly impacting the developing larvae inside the nest.
Providing a shallow water source is also helpful, especially during hot, dry periods when the bees are actively foraging. A simple, shallow dish filled with water and small stones or marbles allows the bees to land safely and drink without the risk of drowning. Placing this water station near the nesting or foraging areas ensures easy access to this resource.
Carpenter bees overwinter as adults within their wooden tunnels. Leaving the established nesting sites undisturbed throughout the winter months is necessary for their survival and subsequent emergence in the spring. Ensuring the nesting areas receive sun exposure helps the bees warm up and become active earlier in the morning, optimizing their foraging time.