Mason bee, a solitary worker bee that burrows in the ground

Mason bee on wood

Mason bee, Osmia, solitary bee… all these names designate the same pollinating insect. And don’t be fooled by its tiny scale! It is indeed able to pollinate as many flowers as its more famous cousin, the common honeybee.

Read on to learn more about this little-known pollinating insect.

Read also:

The solitary bee: key facts


When we talk about the mason bee, it’s actually a catch-all name that encompasses a great many species with different characteristics. They do, though, have a few things in common:

  • Small size, less than half an inch (8 to 12 mm); the carpenter bee (Xylocopa violacea) is the only exception, since it’s over an inch long (2 to 3 cm).
  • A body covered with thin hairs that help disperse pollen.

Colors vary greatly depending on the type of bee. Here’s a short list of the main colors you’ll find:

  • classic yellow and black stripes for the ivy bee (Coletes hederae) and the wool carder bee (Anthidium manicatum);
  • pure black for the blunthorn bee (Melitta haemorrhoidalis, which also goes by the name “carpenter bee”);
  • and rust for the tawny mining bee (Andrena fulva) and the orchard bee (Osmia cornuta).


No need for a hive for the “solitary bee”. As the name shows, it isn’t a gregarious insect (which the common honeybee, on the other hand, is). Most of the time, it lives alone in the burrows it digs out for itself underground.Some species take advantage of holes they find in dead wood to set up their nest.

Mason bee emerging from a hole in the groundActually, it’s pretty common to see one of these insects wedged in a crevice around your doors and windows. Rest assured: they won’t cause any damage at all. However, the carpenter bee does help reveal how strong your wood still is. Indeed, the female will only dig a nest out in old, soft, wood that’s already nearly falling apart. If you notice any in the beams holding your house together, time to start thinking of replacing them.


Whether it’s an adult or still a larva, the carpenter bee feeds on pollen and nectar. Nonetheless, as with every species, different individual bees might have different diets:

  • Lifecycle of the mason beesome of them are in fact only attracted to a single particular species of flowers;
  • others will visit all flowers that are the same color, whatever the species;
  • and, lastly, some will land on anything that remotely resembles a flower, without distinguishing any of them.

On top of this, they won’t be active at the same time. From Spring to Fall, each species will be active and dormant over different periods. Since the larva can’t forage on their own, females prepare a chamber for them which they then fill up with a paste of nectar and pollen. There’s enough food for the larva to grow and turn into an adult, while staying safe from any predators on the outside.

Benefits of mason bees for a gardener

The mason bee is a particularly hard-working pollinator, which needn’t fear comparison to its more famous relative, the common honeybee. It thus plays an essential role in parks and gardens. Thanks to this bee, flower diversity is preserved and encouraged, and crops are more productive wherever we expect harvests, such as orchards and vegetable patches.

How to attract mason bees to the garden

Make your garden appealing and Osmia will appear on its own. Whether in the vegetable patch or in the orchard, you’ve got several options to try out. Best of course is to try them all at once! You’ll be sure to welcome a few at least of this excellent pollinator on your plot.

Provide the bed…

Since mason bees nest either in the ground or in holes it finds in old wood, it makes sense to give it a bit of both. That way it’s sure to find shelter!

  • Mason bee shelter in an old logA great way to go forward is to set up nesting sites directly in the ground. For instance, rake up a mound of soil, and create a “cliff” on one side of the mound with a spade. Pull weeds out from around that area to help the bees find their way to it.
  • A favorite for children and adults alike, nesting boxes will be a great help in and around the veggie patch and near your fruit trees. These look like bundles of short bamboo or hollow cattail stems, bricks or logs with lots of holes drilled into them, etc. They’ll help increase the productivity of your plants! Place them a bit higher up, not on the ground. 3 to 6 feet up is fine (1 to 2 meters). Try to protect these “insect hotels” from wind, rain, and foul weather, too.

…and the breakfast!

The mason bee’s main food source is pollen and nectar. Grow flowers that have abundant amounts of both. Favor heirloom species, especially those with simple flowers (not double or semi-double blooms). Wildflowers are best. This is because many of the modern double-flowered or pompom-like flower varieties sold in stores have much less pollen. A few ideas:

  • sow swaths of flowers, replacing the lawn in some parts of the garden. Annuals and biennials are good for this;
  • make sure some type of flower is blooming at any given time of the year from the beginning of Spring up to the end of Autumn;
  • increase the diversity of flower species to make sure the different types of mason bees find something to their liking.

Although it may be small, the mason bee is clearly a beneficial insect for the garden, and a great helper for the gardener! They complement honeybees in their tasks, a much needed help since numbers are dwindling across the entire planet.

Credits for images shared to Nature & Garden (all edits by Gaspard Lorthiois):
Hairy bee by Björn under © CC BY-SA 2.0
Burrowing by Benjamin Watson under © CC BY 2.0
Hiding in a flower by Lukas Large under © CC BY-SA 2.0
Heading home by Gilles San Martin under © CC BY-SA 2.0