Leafcutter Bees: A Beginners Guide
What are leafcutter bees?
Leafcutter bees are solitary bees. This means that they live alone and not in a hive, like honeybees. They make use of natural tree cavities to lay their eggs in and use leaves and flower petals as nesting materials. Hence their name; they cut small semicircles off of leaves. However, they rarely do damage to plants. The leaves they cut are used to create nursery chambers for their eggs. Think of this like a protective incubator made out of leaves, filled with nectar and pollen that will feed the egg as it develops into an adult bee.
During the process of gathering food supplies for their young, leafcutter bees pollinate your garden. As they forage flowers, pollen sticks to their hairy abdomen. While making their way back to their nesting places, some of these pollens will fall off their hairs onto different flowers, cross-pollinating them. They are such effective pollinators that they can double (sometimes even triple) your yield!
Life-Cycle of the Leafcutter Bee
Leafcutter bees make their entrance into the gardens when temperatures reach a consistent 24C and the summer flowers are blooming. They will chew their way out of the nursery chambers they overwintered in and emerge eager to have their first sip of nectar. Soon after emerging they will mate and start working on their nests; gathering leaves, flower petals, nectar and pollen. Slowly, over the next couple weeks she will create approx. 15 nesting chambers that contain the new generation of leafcutter bees. Your bee house is the perfect place for her to lay her cocoons in. Unlike mason bee eggs, some of these eggs might hatch in the same season that they’re laid in. In early fall you’ll start noticing a decrease in leafcutter bee activity in your garden. The eggs will no longer develop and will stay inside their nursery chambers during the winter.
Note: Next, we’ll tell you how to harvest and incubate leafcutter cocoons. If this is the first year you host them and purchase cocoons from a store, there is a good chance that they’re already incubated. If this is the case, they should be placed directly inside the bee house upon purchasing them! There is no need to incubate your bees the first year.
How to harvest leafcutter bee cocoons
If you host mason bees, you’re used to taking apart the nesting tubes in the fall to harvest cocoons. This is not what you’ll do with leafcutter bees! After you notice there is no longer any activity, it’s time to take your bee house inside. This will prevent wasps and woodpeckers doing any damage to them. The tubes (or nesting trays), that contain the leafcutter bee eggs, will stay intact during the winter. The filled tubes have been capped with leaves to provide a safe and warm home during the colder months. Store the tubes with the leaf-capped ending facing up in a garage or shed for instance (in a cool place, but do not put them in the fridge!). You can place the entire tube or nesting trays inside an organza or BeeGuard bag for extra protection from pests.
Around the time that the dandelions begin to grow, is when you’ll start preparing to put your leafcutter bees outside. You start by harvesting last-years leafy cocoons from the nesting tubes or trays that you stored over the winter. It’s quick, easy and allows you to check for pests and document your bee population. How to harvest your leafcutter bees:
Step 1: Break open the nesting tubes. If you have natural reeds, pinch the end that the bees have capped with leaves, and carefully pry apart the reed, being very careful of the cocoons inside. Paper reeds can be unraveled and most nesting trays can easily be opened with the help of a screwdriver or popsicle stick.
Step 2: The leafy cocoons are now exposed. Carefully separate the cocoons from each other and place them in an organza or BeeGuard bag. You will store them in this bag during the incubation period.
How to incubate leafcutter bees
Step 1: Place the organza bag that contains the cocoons in a dark warm room. For instance, the room where your water heater is located. As they overwinter as eggs inside leafy cocoons, they have to be warmed up to start developing into adult bees. This is what we call the “incubation” period. It’s not the same as incubating eggs, where you place them in an incubator. Instead, we’re trying to simulate warmer outside temperatures.
Step 2: Check periodically if any bees have emerged from their cocoons. At a temperature of 30C, the adult bees start to emerge approx. after 20 days. At a lower temperature of 21C it will take them around 42 days to emerge. Tip: Try to time the release of your bees with the blooming period of your summer flowers.
Step 3: When the first bees emerge, it’s time to put them and the other unopened cocoons outside in your bee house! Place them in the open attic above the tubes, not in the tubes themselves. If your bee house doesn’t have an attic, you can put the cocoons in a small cardboard box (tea box) with an opening on one side and tape it to your house.