Making Homes for Native Bees – A Chat with Dr. Holly Walker

Learn about the diversity of native bees and the types of habitats they seek in our gardens, backyards and green spaces, even window boxes! Smithsonian Gardens’ Entomologist, Holly Walker, will talk about native bees and demonstrate how to create homes for these incredible little beauties who do so much to help the world around them.

Webinar Video

Websites

• Native plants for your area: https://pollinator.org/guides
• Native plants for your area: https://www.xerces.org/
• Monitoring Lab: https://www.usgs.gov/labs/biml 
• Bee Lawn: https://www.beelab.umn.edu/learn-more/beelawn
• Statistic: http://www.theplantlist.org/ 

For information on pesticides, herbicides, and insecticides please contact your local Extension Agent. They are familiar with local guidelines. 

Q&A from the webinar

Q–Please explain again how you might be able to remove tubes from a commercial bee house (you said something about using paper?).  Thank you. 

You can either physically remove the tubes and replace them each year OR make your own slightly smaller tubes out of paper and place them inside the pre-existing bamboo or reed tubes in the bee house. At the end of the season pull the paper tubes out and replace them the following year. Just make sure to monitor them for mold and excess moisture. 

Q–Can you clean the tubes and reuse? Or better to throw them out? 

It is better to throw them out because they could be harboring diseases, molds, and mites that you do not want to transfer to the next generation. 

Q–What is the maximum or ideal tube length??? 

Most of what I have read says that 6 to 7 inches is the ideal tube length. Again, shorter tubes run the risk of producing only males which will not help you raise the next generation of native mason bees. 

Q–For human-made bee homes- 1) Does it matter if the house is on the ground vs. above ground (if so how high) 2) Does it matter if they are in sun or shade? 

Mason bee houses on the ground tend not to do as well, and so the recommended height for them is 6-7 feet from the ground, though many people hang them closer to 5 feet so they can monitor what is going on inside. And yes, sun does matter. Since these are early spring species, they need that early morning sun to help them warm up enough to fly. Earlier flight times means more time foraging and ideally overall success. If possible, try to position the bee house facing south or where it will get a good amount of morning sun. 

Q–If I pull the tubes in in the fall — when and where do I put those back out so they can emerge? 

You want to put the tubes out just before temperatures start reaching an average of 50 degrees during the daytime.  Depending on where you live this is often late February or early March. You can put last year’s tubes in a box or plastic container that has a hole cut out of the side, or if your mason bee house has extra space you can place them in there next to fresh tubes. 

Q–Can you give examples of hollow stem plants? 

I should have said hollow stems or plants with pithy stems. Some examples include Joe Pye Weed, elderberry, raspberries, and grasses such as little bluestem and switchgrasses. 

Q–How do I find plants that don’t have neonics? 

If you are worried that plants you have purchased may have neonicotinoid pesticides or other harmful pesticides on them it’s a good idea to ask the grower or nursery you buy them from. Organic farms will not use these pesticides, though there are organic pesticides so that doesn’t always mean pesticide–free, but they generally tend to be much safer for pollinators. Another option if you have the space is to grow your own or check out local plant swaps as most home gardeners do not use these types of pesticides. 

Q—Are vegetable gardens good for bees? 

They can be. Remember that many plants require bees for pollination and even garden plants that produce vegetables and fruits often need pollinators to complete their lifecycle. Plants such as squash, cucumbers, and many types of berries such as raspberries and blueberries rely on local native pollinators. Tomatoes need native bees such as bumblebees who perform buzz pollination to set fruit, so they really have evolved together. 

Q–I live in Wisconsin and they say I should bring the mason houses into a warmer spot, so they don’t freeze. It seems inefficient. Where are the mason bees naturally in the winter? 

They are outside. But even in nature a certain number of native bees don’t make it for various reason including freezing. Sometimes depending on the material, if it cracks or moisture gets in there, it can cause damage or kill bees in the winter. That’s nature, but if you are actively trying to rear mason bees people tend to take extra steps to protect them from both the weather and predators. By placing them inside a NON-HEATED structure through the winter you lower their risk of dying from cold and predation. 

Q–Do bees sleep in winter or, do they collect honey in the winter too? 

It depends on the bee. Honeybees do not hibernate and will continue to collect pollen in the winter if the day is warm enough. But for native bees, they have mostly evolved in those areas where it gets cold enough for them to go dormant during the winter. They are either hanging out as adults or pupae inside their cocoon cells waiting for the spring. 

Q–Are soaps also as bad as pesticides? 

It depends on how you use them. Insecticidal soaps or homemade soap solutions penetrate the cuticles between the plates on most insects and can cause desiccation and will kill cells in the insect. They can also clog the breathing opening on insects, suffocating them. For this to happen you must coat the insect with the soap. That said, if you spray a bee with insecticidal soap it will mostly likely kill or harm them. But once the soap has dried on a plant surface it is generally safe for bees and other insects. 

Q- Do leafcutter bees live on a leaf? 

They do not really live on the leaf. They collect parts of leaves and may rest on them, but they live so to speak either in the hollow tubes, tunnels, or stems as immatures. As adults they spend the rest of their time foraging in the landscape. 

Q- Have the types of crops we are raising on an industrial scale affected which bees are prevalent in an area? 

They do; literature and research suggest that large scale crops can decrease pollinator diversity and therefore decrease local pollination services. Here is a good article to read if you want to dig in further: Large-scale Trade-off Between Agricultural Intensification and Crop Pollination Services. 2014, Frontiers in Ecology and the Environment, Nicolas Deguines, et. al. 

Q- Do all bees sting? 

No. First of all, male bees don’t sting at all since the stinger is a modified ovipositor. But there are entire families of bees that either have no stingers or their stings are so reduced that they effectively couldn’t sting you. Bees in the family Andrenidae, for example, are often referred to as stingless bees for that reason. But in general, most bees, especially native species, are very docile and highly unlikely to sting unless they get trapped against you. 

Q—Regarding ground nesting bees, is open soil under plants ok? In other words in ground covers or dense plants? 

Most ground–nesting bees seem to prefer bare, sandy, sunny soils for nesting in. It’s commonly thought that this has to do with temperature regulation in bee species, but especially with ground nesting bees. That said, if you have some plants that aren’t planted too densely and still allow for a good amount of light to reach the soil then I think it would be fine. 

Q–Native bees used in orchards–how is their labor recruited? 

To recruit native bees, specifically orchard bees, you need to create resources for them. You can start by planting other early spring–blooming plants near your fruit trees to help entice them in. You can put up the mason bee houses that we talked about to help encourage them to reproduce for generations in your orchard or nearby. Make sure you do not use toxic insecticides and that you provide those other resources they need, such as mud to fortify their cocoon cells. There are also commercial companies that you can buy orchard bee cocoons from and they will help you set up your location for them. 

Q–Can you please show the suggested plants and trees that supports native bees? 

 Here is a very general list: 

• Asteraceae (aster family): Coreopsis, Helianthus, Rudbeckia, Solidago 
• Berberidaceae (barberry family) 
• Ebenaceae (ebony family) 
• Ericaceae (heath family) 
• Fabaceae (pea family) 
• Fagaceae (oak family) 
• Grossulariaceae (currant family) 
• Rhamnaceae (buckthorn family) 
• Rosaceae (rose family) 
• Scrophulariaceae (figwort family) 
• Eastern Redbuds  
• Pussy Willows  
• Cockspur Hawthorns 
• Basswood 
• Blueberries