Editor's Note: This story was originally published in 2019.
When Dyan and Mark Eisenberger decided to make their garden in Columbia more pollinator-friendly, they started by removing nonnative plants. They planted flowers to attract insects. And they added a few bee houses.
Some of these bee houses were made by drilling holes into slabs of barn wood. Some were made from sticks and reeds foraged from their own garden.
In a few hours one afternoon, they watched mason bees going back and forth, stocking the house with nectar and pollen for the next generation. The bees finished by sealing each egg-filled tunnel with mud.
“It’s amazing to watch them,” says Dyan Eisenberger.
The bees were fun to watch and they also work hard to pollinate many of the plants in her yard. Mason bees don’t build hives, so people can give them a hand by adding houses suited just for them. If you build it right, they will come. However, some mason bee houses actually can harm these important insects.
The mason bees are among 400 species of bees found in Pennsylvania. While honey bees get a lot of attention, mason bees play an important role, especially for many native plants, fruit trees and vegetable plants.
The mason bee is a native bee that emerges early in spring, just in time to pollinate apple, cherry and plum trees. One type of mason bee, the blue orchard bee, visits more flowers per minute than European honeybees and are more efficient at transferring pollen between flowers, bee researchers have found. They also don’t mind foraging on cold and cloudy days.
If you’re worried about bee stings, solitary bees like mason bees are not aggressive. They won’t try to sting people unless stepped on or grabbed, according to Penn State Extension.
In the wild, mason bees nest in abandoned beetle burrows in dead logs and stumps. So adding a nesting box will help bees nurture the next generation and boost pollination in your garden.
To make your own mason bee house follow these tips from Dyan Eisenberger, a Penn State Extension master gardener, National Wildlife Federation and the Sustainable Agriculture Network.
When to build
Mason bees are active from mid-April to mid-June. So you’ll want bee homes in place by April. Adults emerge in April to mate and then females look for a place to make a nest for their eggs.
Once the larvae hatch, they eat stored pollen and nectar and by the middle of summer spin cocoons in the nest. They emerge as adults in late summer and overwinter in the nest.
- Mason bees lay eggs and store pollen and nectar in hollow stems or crevices. (The first eggs are laid at the back, and each egg is separated by mud.) You can make a mason bee home with a wooden block filled with drilled holes or a bundle of straws or bamboo shoots.
- Don’t use treated wood, which can harm the bees.
- To attract the most bees, tunnels should be 5/16th of an inch in diameter and 6 inches deep.
- Cover the fronts of the holes with chicken wire to prevent bird attacks.
- Place the box at least three feet above the ground.
- A roof on the house will protect from rain so the young bees won’t rot.
- The front of the home should face south or southeast so cold-blooded bees can be warmed by the sun and start the day’s foraging.
Because parasites and fungus can fester inside the tunnels of a mason bee house, the tubes should be cleaned every year or the nesting material should be replaced. The best time to clean is after the adults leave the nest in early spring and before females start laying eggs. To clean, squirt chlorine bleach inside each hole and rinse.
Grow plants nearby for mason bees to gather nectar and pollen. The bees have a 100-yard foraging range.
The bees look for plants that flower when they emerge from their homes in mid-April. They like plants such as sweet pea, delphinium, ranunculus, bleeding hearts and violets and even weeds like dandelions, chickweed and ground ivy.