Things to Consider When Contemplating a Mason Bee House and Spring Mason Bee Stewardship Tasks
Mason Bee Considerations
It’s nearly spring which means it’s time to think about spring mason bees. These solitary and docile bees are a joy to watch provision their nests in the spring. In Vancouver we have a number of native mason bees (50+ in Washington, unknown how many are present in Clark County) but the main one that gardeners come into contact with is Osmia lignaria, also called the blue orchard bee from the family Megachilidae. These are the best things to think about when considering if you want to keep mason bees:
Do I have a place to keep mason bees? Mason bees don’t need much space but they do need a relatively water tight house, nearby forage (blooms less than 500 feet away), and some mud and water available for nesting. A bee house could go on a patio or deck and should be 3-6 feet or more above the ground. It can be attached to a house or garage and should get some sun, ideally morning sun, but mason bees are pretty resilient to cooler, wetter temperatures as compared to honey bees.
What kind of house should I get? Wood or plastic houses are great but don’t use plastic nesting materials like nesting blocks or plastic straws – they’re a bad idea. Always, always use natural nesting materials made out of paper, cardboard and wood. We also have had bad luck using reeds as nesting tubes like those that come glued inside a cute premade house. These houses are tempting but they are impossible to clean out the bee cocoons without destroying the house. And using bee house for multiple years when you can’t clean them out means a large increase of pests for every year the house goes uncleaned. We’ve also had good luck using something called an emergence chamber (read more below) to get the bees out of the less-than-ideal bee house and into a new, easily cleanable house. If you have a larger space, having multiple small houses is preferred to having one large house as multiple houses keeps disease at bay. But we like plain, houses that keep the water out of and off the tubes or nesting blocks. We prefer tubes or nesting blocks as they are the most easily cleanable.
What are ideal house placement conditions? We have found that mason bees like some sunlight but too much sunlight can cook their larva and kill them so someplace where it doesn’t get too hot is best. South or east facing houses seem to do best and placing them on the east side of a north-south trending fence gives them morning sun, assuming your site isn’t too tree-filled, and shade in the afternoon. Having a nest on a post where it gets full sun and full wind exposure can be fine but if we have a cold spring the bees may not do well in an exposed setting and in our changing climate our springs in Clark County can vary. The best advice I can give you is to put it somewhere where you will see it daily as watching these bees work is a lot of fun.
How close to food sources does my house need to be? This is important because research shows that most mason bees only travel 300 to 500 feet to forage which means that there needs to be close food in order for the bees to be successful. We’ve seen mason bees on many native and non native plants but in general mason bees seem to like many of the typical early blooming plants we have in Clark County like heather, rosemary, fruit trees, and dandelions. If there isn’t enough food near your bee house, wild bees won’t find it to nest in and any bees you’ve put in your house to hatch out may either be unhappy and leave or be unsuccessful and die. Either way you need close resources for these bees to be successful.
When should I put bee cocoons out and where can I get some mason bees? Places like Backyard Bird Shop locally sell the blue orchard bee in tubes or folks will sell cocoons. Smaller cocoons are male and larger are female. Most bee tubes will have 9-12 bee cocoons inside and generally 1-2 tubes will populate a bee house – it doesn’t take a lot. VBP has bees available this spring as well and we will give them out with the purchase of some new bee houses we will be selling soon but we also have had some bees donated to us and we will give those out for free to folks who need them so just ask! We typically tell folks to put bees out when the weather is going to be 55 degrees or more for a few days in a row and when there are some flowers that are starting to bloom as mason bees have immediate food needs. We usually tell folks to not put bees out until at least March 15 in Vancouver and early to mid April or later if you’re at a higher elevation. Remember, bees need food available and if you have them stored in a cool place like a garage or refrigerator they will be happy to stay in those locations until the flowers they like are blooming.
Spring Mason Bee Stewardship Tasks
For now, you can focus on a few chores to get ready for spring mason bees:
Cleaning out old bee houses. Now is a great time to clean out your old houses especially if you’ve cleaned out the bee cocoons in the fall. Make sure and attend our annual bee cocoon cleaning event in October to learn about that process. The bee houses will have dried mud and pollen and other insect bits that have accumulated over the year. Take out any old tubes or used trays and wipe out mud and debris with a dry cloth or sponge. Once you have it as clean as you can use a dilute bleach/water solution (1Tb bleach to ½ gallon water) and wipe down the inside areas of the bee house and make sure and clean out any mold or larger debris first. Give those wood nesting trays, if you use them, a wipe down as well. For difficult debris we use a pipe cleaner. Remember if you get mud wet it gets really sticky and greasy so getting as much of it out before hand is best. Let everything air dry.
Emergence chambers for less-than-ideal houses. If you purchased a bee house that uses reeds that you cannot remove or some other set up that is not easy to clean out, we recommend encouraging those bees to emerge and move to a new house that is easier to manage. The best way to do this is to set up a mason bee emergence chamber to guide the bees to the new house. We used a bucket but any container works. If you have a larger bee house, you may want to use a plastic tote or box you have available that’s appropriately sized. You drill one or two 9/16 diameter holes in the chamber and put the bee house inside and place the entire thing under the spot you will place your new, more easily managed mason bee house. When the bees emerge, they will leave the chamber and not be able to find their way back in and will be likely to find the new house placed above it.
Be Patient! There is no reason to stress over mason bees but the biggest thing they need is food that is close to the nest and that food won’t be out in force until late March/early April. The bees will emerge when it’s right for them to emerge but there’s no reason we can’t be good stewards and help them be successful – we have access to weather forecasts after all. In 2022, mason bees at my house started emerging around March 19 when we had a very warm later winter/early spring only to have snow in early April. In 2023 we’ve had a much cooler and wetter later winter so it may be a later season this year for mason bees – and that’s OK. With a little planning we can be good stewards for native bees and help mason bees thrive in our yards and public spaces.