When native plants start to blossom set out clean Pro Bee Blocks and any colonized nests from the previous season. If you have purchased bees when you receive them place them in the fridge until the first flowers appear.
Look carefully at the cocoons and you will notice one end is smooth and the other end has a nipple. The nipple is the head end. The smaller cocoons are the males and they will hatch first.
There are two ways to release the bees for hatching. You can put them in a mouse proof container with a hole on the side near the bottom for the bees to crawl out from. The hole only needs to be about 5/16 inch. The container should be very near the Mason bee home.
You can insert the bees into the tube in your Mason bee home. Care must be taken that the nipple end is towards the front of the hole or they will face the back when they hatch and be unable to turn around to get out. You can put one cocoon per hole or many if you want. As long as the large cocoons [females] are at the back. Once the cocoons are inserted tip the home back so they slide to the rear of the hole. You are now ready to put the home out in your preferred location.
You want the home to have morning sun on the hole entrance which will warm up the bees and get them working earlier. I watch the colonized Pro Bee Block and when the majority of the holes are open and the new block has a lot of activity chances are most of the bees have emerged from the old Pro Bee Block. Through observation you will learn to tell when to take down the old Pro Bee Block.
If you are not sure if all the Mason bees are out you can put the block into a cardboard box with a 3/8 hole in the side near the bottom edge and place it near the new Pro Bee Block. When the stragglers emerge from the block they will go to the light from the hole and join the working ranks. You can actually do this at any time, even before the first bee hatches out.
If you see a Mason bee going in and out of the cardboard box don't worry it may be trying to nest inside, when you remove the Pro Bee Block for cleaning it will go elsewhere. Additionally if you see a Mason bee that has gathered pollen, yellow on the bottom of the abdomen, going into a old hole before your ready to take the old block down, it is easily stopped by inserting a 2 inch common nail to seal off the hole, pointy end first until the head is flush with the edge of the hole. Of course wait till the bee is not inside!
Once your previous seasons Pro Bee Block is empty it can be cleaned and put back up to multiply your base population or if you're happy with the number of bees you have, stow the block away for next year. The thing to remember is you always want to have a clean block on hand for next season. Cleaning is easy; submerge the block in a bucket of water, maybe put a rock on it to hold it under, for ten minutes. This will loosen all the debris in the holes, and then use the garden hose to blast everything out. To sterilize put it in the oven at 150F for ½ an hour and your annual maintenance is done.
You have enjoyed watching your Mason bees for the last 5 or 6 weeks. The bees are no longer coming and going, nesting activity is over. Hopefully you now have many sealed holes filled with next years developing bees. Now you want to carefully store your blocks, out of any direct sunlight, in a dry shed, garage etc. to keep them away from outside predators. Be very careful not to bump them.
It is important that the storage place will not heat up much beyond ambient temperatures as this will accelerate their development and they will be fully formed before proper hibernation time. The danger of this is that they will now prematurely be living on their body fat reserves and will be in a depleted state when winter rolls around and chances are they will starve to death or emerge in the spring in a weakened state.
When storing, place the blocks with the cavity entrance the same as when they were hanging on the wall. The larvae orientate themselves so they don't develop facing the back of the hole which is a death sentence- as they attempt to emerge they move toward the inner portion of the nest and ultimately die within the nest, possibly killing other bees in the process. If you stack blocks on top of each other, make sure to insert a spacer to allow airflow over each block.
Watch your well pollinated crops grow while your bees are busy in their homes developing.
Enjoy your harvest! Your bees are now fully developed in cocoons entering hibernation and waiting for next spring. Ensure your blocks are not subject to extreme cold but not warm either: 32F - 41F (0-5C) is a good range. Don't worry too much about it; if your bees are from your area, ambient winter temps are what they are accustomed to. They can stand weeks of freezing temps. Some people store them in a refrigerator.
Christmas is coming! Mason bee homes are great gifts especially if you've had the foresight to have additional blocks partially colonized that you can pass along.