When Do I Release My Mason Bees?

There is not a perfect day of the year to release mason bees for every area. Climates and temperatures vary from year to year so it is necessary to base bee release on signs that spring is in full force. Determining when to release mason bees (or any solitary bee) is easy if you know the signs to look for. We will get to those signs in a bit but first lets talk about what we are trying to accomplish with timing the release.

Our goal is for the maximum number of pollinators to be alive and working on our blossoms. This will ensure more pollination and a higher yield as well as better bee reproduction.

WHY NOT LEAVE THE BEES OUTSIDE ALL YEAR?

Tunnel nesting solitary bees find nesting materials wherever they can. Usually nesting in dead trees and wood pecker holes. The tunnels are spaced over a greater distance than in a bee house.  Casualties in natural bee nests as well as in bee houses happen during the winter months when foragers are hungry and food is scarce. The appeal of a bee hotel or bee house is a lot more tempting to foragers (and other pests) than locating individual bee tunnels. There is less work for the reward.  To protect the bees from predators we recommend cleaning out the bee house in the fall and storing the bees for winter hibernation. Learn about clean out here.

WHAT HAPPENS IF I RELEASE THE BEES TO EARLY?

There are two potential problems with putting up the bee house early.

  1. Predators- the more time the bee house is put up the more likely something or someone will find it to good to pass up. Protective measures can be done like adding wire mesh to the front of the holes and putting the house in a protected location. (For other ways to manage pests click here.)
  2. Early emergence and frost. Solitary bees are temperature sensitive. Consistent temperatures signal to developing bees when to develop, hibernate and emerge. Different species of bees have different temperature signals. For example, Blue Orchard Mason Bees (early spring time bees) emerge when day time temperatures are consistently 50-55* F. Where as, Alfalfa Leafcutter Bees (summer time bees) emerge when day time temperatures reach a consistent 70*F.

If there is an abnormal warm spell followed by a frost it can kill the emerged bees.

 

WHAT SIGNS SHOULD I NOTICE BEFORE RELEASING MASON BEES?

Budding branches are the most reliable sign for releasing mason bees. It is time to put up the bee house when the buds on the branches are about to bloom. There will be plenty of blossoms for the bees to pollinate.

When day time temperatures are consistently in the 50’s (Fahrenheit) start watching for buds on your branches. It is about time to release your mason bees. Consult the Farmer’s Almanac to find out when your area is usually at these temperatures and set a reminder (on your phone or calendar) to remind you to put up the bee house.

Wait until the chances of frost are low.  It may help to consult The Farmer’s Almanac for your region to know when chances of frost are low. Find The Farmer’s Almanacs frost dates here.

WHAT ABOUT SUMMER TIME BEES?

Summer time bees can be released in the same nesting area (bee house) as spring time bees. They can be released at the same time and they will emerge when the temperatures are right for them.

If summer time bees (Alfalfa Leafcutter bees and Sunflower bees) are the only bees in a bee house  we suggest putting the bee house up in May. It takes about a month of warmer temperatures for the leafcutter bees to finish developing. They will usually emerge in mid June-July.

Check out These other posts about releasing bees:

SEE NEXT STEP- SETTING UP YOUR BEE HOUSE