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102-The Pollinating Power of Solitary Bees, and How to Attract These Gentle Insects To Your Backyard Garden

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Save the bees! That’s a statement becoming more commonly heard these days. The decline in honeybee populations has been a hot topic in recent years, but there is another story to be told. Our greatest ally in the home garden and food production across the U.S. isn’t the honeybee at all – it’s actually the solitary bee species.

My guest this week, Dave Hunter, is an expert on the subject of solitary bees. We first met when I visited his Seattle, Washington-area home for filming of (you guessed it!) an episode of Growing a Greener World®. He walked us through the world of the solitary bee and the benefits they offer in the garden. We were also fortunate to enjoy a tour of his company, Crown Bees. Dave and his team are devoted to promoting gardener awareness and solitary bee populations across the continent – particularly, the mason bee species.

 

Dave Hunter

Dave Hunter is a wealth of knowledge on the subject of solitary bees, and he’s keen to increase gardeners’ awareness of these important species. (photo: courtesy Dave Hunter)

 

What is a solitary bee? Just 10% of all bee species are considered “social” bees. They form hives – with a queen, drones, workers, etc. – and include honeybee and bumblebee species. The remaining 90% of bee species – the solitary bee – nests and works alone.

Every female solitary bee is a queen. She lays eggs, but she also gathers pollen, protects her eggs and does all the jobs of the honeybees buzzing around in a hive. Well – except for fertilizing her eggs. That’s the job of the male solitary bee but more on that coming up.

Solitary bees are less aggressive than social bees. When you consider that the primary job of many social bees is to protect the hive – the honey, the queen, and the eggs within – it’s easy to understand why they might get feisty when you get too close.

Solitary bees, on the other hand, are too busy doing all their own work to be aggressive guardians of their nests. They rarely sting, and their sting feels much more like a mosquito bite than the searing pain of a social bee sting.

Here’s another interesting fact: Honeybees are not native to North America. They were brought to this continent by the pilgrims. (Those early settlers also brought with them dandelions as a pollen source, by the way. Thank you, pilgrims.) In fact, none of the species native to North America make honey. I love honey as much as the next person, but what I love even more is pollination in my garden.

 

mason bee

This gentle mason bee is a solitary bee species and a valuable pollen spreader in the garden. (photo: Karl Alexander)

 

Why Bees Matter

Fruits and seeds require pollination to form. Pollen must be moved from male to female parts of flowers in order for the flower to transform into the fruit or seed that we consume and which will produce more of that plant for future yield. Dave reminds us that the seeds and fruits we humans don’t consume are also critical to other creatures in our ecosystems – like quail and mice. Without pollination, all of the creatures of this planet – great and small – would be at risk.

Within the insect world, bees are some of the greatest pollinators. One quarter of the food we eat is pollinated by the honeybee species, but there are approximately 4,000 bee species in North America. Four thousand species!

Those different species of bees pollinate differently too. Honeybee and bumblebee species are considered pollen gatherers. You’ve probably seen bright yellow pollen stuck to the hind legs of these bees. Well, that’s sort of the problem. The pollen sticks to them. Some of that pollen does occasionally remain on a flower they visit, but more often than not, the pollen sticks on the bee and is taken back to the hive.

Solitary bee species, on the other hand, are considered pollen spreaders. Since they don’t live in social hives, they require less pollen as a food source. Their bodies aren’t designed to hold pollen like the bodies of social bees. Most of the pollen gathered on the body of the solitary bee quickly falls off – and on to each of the subsequent flowers that bee visits.

In other words, solitary bees are doing much more of the pollination work than the beloved honeybees – 30-60% more, actually. You might say they are the unsung heroes in the garden. The honeybee may get all the limelight, but the solitary bee is the one to really get the job done.

 

mason bee

The mason bee on this strawberry bloom is picking up pollen all over its body. The pollen will fall off on every subsequent flower the bee visits. (photo: Karl Alexander)

 

Solitary bees stick closer to home too. They will travel in a 200-300’ radius to find pollen, while honeybees wander up to two miles. That means that the solitary bees are focusing their pollination work in your garden instead of the landscapes a mile or two down the road.

Raising honeybees can be a lot of work. I ought to know. I have hives here at the GardenFarm™, but it’s been a struggle to keep those hives going. I’ve lost a number of hives, and that can be frustrating. Sure, the honey produced by hives is a big plus, but if you’re a gardener who wants to boost pollination without taking on an additional project, solitary bees are the ticket. Not to mention, you’ll be supporting your ecosystem to boot.

Snug As a Bug In a … Nest

So, where do solitary bees live? Most – 75% or so – nest in the ground, while others nest in small holes in trees or reeds or some other tiny opening in the natural environment.

With our increasingly urbanized society, the nesting habitats of solitary bees have been disappearing. The reeds and tiny branch nooks and other small natural recesses have given way to asphalt, concrete, carefully manicured and managed garden beds, and groomed expanses of lawn. That development has pushed out many of the ground-nesting bees too. Bees have a difficult time building nests in the heavily-rooted surface of our lawns.

Not to say that there aren’t solitary bees where you live. Odds are good that they are out there – they just might not find your neighborhood to be a hospitable environment to live.

 

solitary bee habitat

The best location for a solitary bee habitat is facing east or southeast on a sturdy post or wall. (photo: Karl Alexander)

 

It’s time to change that. Here’s the good news: It just might be one of the easiest changes you make in your garden.

When I visited Dave for Growing a Greener World, he showed me how to make a solitary bee “house” or bee habitat. It’s an easy DIY that you can build using items you probably have at home right now.

Dave explains that the best materials for solitary bees are natural, of course – no plastic, ceramics, etc. Stick with paper, reeds, wood, etc. and gather the items into any type of container to create a house. The only reason for the container is to protect the tubes you’ve created out of those natural materials. Solitary bees need their nests to remain dry, so anything which will protect the tubes from rain fits the bill.

You’ve probably seen solitary bee habitats for sale at the big box stores. We’re all busy these days, so the convenience of picking up something already built for you is pretty tempting. However, there are downsides to this option.

Years ago, Dave’s biggest competitor was ignorance about the importance of bees. Today, his biggest competitor is poor quality habitats which can hinder, rather than help, the home gardener to increase their bee population.

Most of the houses or habitats sold commercially are built out of bamboo from China. Yes, bamboo is a natural material, but it has two big drawbacks:

  • Most of the holes of bamboo stalks are roughly the same size
  • Bamboo is tough – and that means tough to open up

When it comes to solitary bees – size matters. There are bee species both large and small and everything in between. Each species requires holes of a different size in which to nest. Mason bees, for example look for holes which are ⅛” to ¼” in diameter.

 

solitary bees

Although they are referred to as “solitary bees,’ they do interact with other bees in their species. Seen here four mason bees travel back to their individual tubes sheltered within the same habitat. (photo: Karl Alexander)

 

If your store-bought habitat features one-size-fits-all bamboo stalks, your locally-native solitary bees might not accept your invitation. Remember, those solitary bees are probably out there, somewhere, in your environment. When they are looking for a place to set up shop, you want them to pick your garden.

It’s also been discovered recently that, when holes are all the same size, the house is more likely to attract pests, and the pests will outcompete the bees. So, better to mix up your materials – and as a result, the size of the juxtaposed nesting holes.

Solitary bee houses require yearly cleaning. That may seem strange, since the best habitats are made of natural materials, and these nesting spots aren’t cleaned in the wild, right? Well, Dave points out that our gardens are not natural environments either. They require our care – watering, weeding, pruning. They also produce more pollen (and probably a greater number of pests and chemical residues) than wild spaces.

That creates an unnatural pressure on the house environment, which is why a yearly cleaning will keep it healthy and inviting for the next generation of solitary bees. Dave compares this maintenance step to weeding your garden.

Cleaning is easy to do – unless you have bamboo. To clean the tubes, you need to open them up and clear out any debris. Bamboo stalks are too strong to open up easily – if at all.

So, do yourself and your future solitary bee population a favor and think long-term. Opt out of the big box store bee houses. Build your own. An easy and inexpensive option Dave recommends is tubes made of parchment paper. Roll the paper four times around coat hangers, small colored pencils and standard, number 2 pencils to create tubes of variable sizes. It’s fascinating to think of bees so small that they prefer to nest in a tube the size of coat hanger wire!

 

solitary bee habitats

Solitary bee habitats can come in virtually any size and shape – as long as it protects the tubes inside from rain.

 

Fold over the end of each tube and gather the tubes into some sort of container to protect them from the elements. The best place to site your bee house is on some stationary area – like a wall or fence post – at approximately head height. Face the front of the house to the east or southeast. Solitary bees emerge with the warmth of the morning sun.

I have to admit, I probably spent far too long standing transfixed in front of the bee house I mounted at the GardenFarm. It was fascinating to watch the bees emerge for the first time and to stand so close to the house as they buzzed past me on pollen-gathering excursions. They really are incredibly gentle creatures.

When the Bees Won’t Come

Solitary bees look for three things when choosing a territory:

  • Appropriately-sized nesting holes
  • Good pollen sources
  • Something to seal and protect the end of the egg chamber within the nesting hole – like mud, tree resin, chewed up leaves, etc. (all depending on the species)

It’s possible that you will place a habitat in your garden and months will pass without a bee resident (or only a few who accept your invitation). There just may not be many hole-nesting species in your area. If that’s the case, you can purchase bees, and Crown Bees is a great resource for that. However, Dave recommends you start with allowing time for bees in your area to show up before you opt to buy.

You can purchase bees from Dave and the team at Crown Bees, but they aren’t actually in the business of selling bees. Their business model is built on a principle of setting up the gardeners across North America to successfully increase their own bee populations.

As the population increases for each gardener, they ship the extra bee cocoons back to Crown Bees. There are thousands of gardeners across the country raising a bounty of bees for Dave to distribute. These are the bees that Dave will ship to gardeners who don’t yet have their own population.

Interestingly if you do purchase from Crown Bees, you’ll likely be receiving bees which were produced in your general area. Dave focuses on keeping bees in their original, native location – by way of a brief diversion to Seattle.

 

solitary bees

These mason bees have recently emerged from their cocoons, ready to explore and pollinate their new surroundings. These creatures are so gentle, they can be handled without any protective gear. Your odds of being stung are very low.

 

Pollination Profusion

Solitary bees are so prolific at pollination work, that they have sometimes overwhelmed commercial farmers with the abundance of crop yield. Farmers in the Nashville area placed solitary bees in their fields and, then, couldn’t keep up with the results. Acorn squash rotted on the vines because the farm operation just couldn’t pick it fast enough.

Studies have shown that cherry orchards double or triple their yield from increased pollination when they incorporate mason bees. Strawberry farms using solitary bees have reported growing half again the volume of berries as before the pollination army arrived. And what home gardener wouldn’t want to see their berry production double?

These species really can create a significant difference in the production of your garden. And – as importantly, they are native species and critical to the health of our ecosystem at large. Promoting solitary bees in your garden is an easy win-win on so many levels.

What’s Happened to the Bees?

It probably won’t surprise you to learn that human activity has been the single, greatest cause of declining bee populations. When we spray chemicals, there are unintended consequences, and bees are a keenly-felt example of that.

Large areas of the southeast were sprayed with chemicals for mosquito control in the wake of the Zika Virus health crisis in recent years, and every other flying insect in those areas was killed too. Katydids, ladybugs, dragonflies, and – yes – bees all fell victim to the lethal power of the chemical spray.

Not all chemicals kill, but they can still have a negative impact. If you treat your lawn, the bees in your area aren’t typically killed, but they do recognize a danger and will leave the area to find a new, less-toxic home base.

Dave encourages gardeners to use fewer chemicals. It’s my hope that you’ll opt to forego chemicals altogether.

When we let Mother Nature work, chemicals are rarely – if ever – necessary. Given the chance, predatory beneficial insects will take out pests. And there are better methods for treating weeds and diseases too.

 

mason bee carrying mud

If you look closely, you’ll see that this mason bee is carrying a tiny piece of mud to seal an egg chamber in this bee habitat. (photo: Karl Alexander)

 

Dave has seen, firsthand, the power of the natural world at work in his garden. When one of his rose bushes was infested with aphids, he did nothing but noticed that all the aphids were gone within a few days. Around the same time, his broccoli was under attack from some form of caterpillar-type pest. Those too disappeared within the week. What happened?

Dave and his wife began to observe ground-nesting hornets on their property and realized that the hornets had sensed the presence of all those garden pests as a food source. The hornets moved in and ate the Hunter family’s garden pest problem away.

Dave hopes that, someday, chemicals will be obsolete in the garden and that gardeners will rely on predatory insects for pest control. He’s got plans to expand his business to include solitary wasps. These aren’t the aggressive wasps we typically think of when we hear the term. There are hundreds of wasp species – many of which are actually mistaken for bees – and they not only pollinate but also feed on pest insects.

There are solitary wasps which, like their bee counterparts, tend to be gentle and great garden partners. These wasps will move into the back of a hole and stuff it with the bodies of hard- or soft-bodied pests and seal them into the hole as a food source for their deposited egg. Someday soon, we may all be turning to Dave and businesses like his to add wasp habitats to our gardens instead of heading to the chemical treatment aisle of the local big box store.

 

mason bee coccoons

Harvested mason bee cocoons shipped to their new home are placed in front of their prepared habitat. These newly emerging bees will make these tubes their new home and where eggs will be laid by the female bees to increase their local population.

 

The Lifecycle

Most solitary bees live just six weeks. Each female is capable of laying around 25 eggs during her brief life. She lays one egg each day and seals each into the tube with a bit of pollen, placing between six and twelve eggs per hole.

The eggs hatch within a couple of weeks and feed off of the pollen left in the hole. At this stage, they remain in the tube and look like small grubs. Ultimately, each grub spins a cocoon and transforms into an adult bee.

Typically, the bees hibernate in their cocoon form through the winter and emerge from the hole as adults in spring. So each female queen is laying what will be next year’s bee population.

Adult males are smaller than females, and they have just one job – mate with the female to fertilize her eggs. Once his work is done, so is the male bee’s lifecycle. It’s the female bees who live on to spread the pollen in your garden and lay eggs to carry on after she’s gone. With each female producing up to 25 offspring, it’s easy to see how quickly a small bee population can grow when provided with good habitat.

Gardeners throughout the U.S. learn through Crown Bees how to gather excess cocoons and ship them safely to Seattle. Then, Dave and his team can – in turn – ship them out to new gardeners just getting started in the amazing world of the solitary bee.

These bee habitats and Crown Bees’ efforts directly impact only the hole-nesting bee species. So, what of the ground-nesting solitary bees? Well, it’s just not feasible to access and move the cocoons of ground-nesting bees. Instead, the Xerces Society suggests providing a clump or two of stable, bare, mounded soil to create potential nesting sites for ground-nesters.

But your awareness of the presence and need for all these solitary bee species can have a big impact on their success too. Become a bee champion. Share this message with friends, fellow gardeners, neighbors, etc. Subscribe to Dave’s monthly BeeMail newsletter. He offers monthly advice on how to be successful at maintaining and increasing your bee population.

 

summer leafcutter bee

This solitary species – a summer leafcutter bee – is carrying home a small bit of leaf. (photo: Karl Alexander)

 

Dave’s website, Crownbees.com, is a fantastic resource too. His focus is on teaching, and I guarantee you’ll learn some fascinating facts and helpful information when you spend a little time there.

I encourage you to spend a little time to listen to my conversation with Dave, too. Scroll to the top of the page and click the Play icon in the green bar under the page title. Dave’s passion and enthusiasm for this aspect of gardening is infectious, and he shares a few more really fascinating facts that are sure to pique your curiosity for more.

Links & References

Episode 007-Organic Weed Control with Jeff Gillman

Episode 009: Organic Disease Control with Jeff Gillman

Episode 067: Predatory Beneficial Insects: Feared Foes of Garden Pests, Pt. 1

Beginning Gardener Fundamentals – my online gardening course

joegardener Newsletter

joegardener Facebook

joegardener Facebook Group

joegardener Instagram

joegardenerTV YouTube

joegardener Twitter

Growing a Greener World Episode 503: Solitary Bees

Growing a Greener World ® Episode 601: Beginning Backyard Beekeeper

GGWTV YouTube

Crown Bees

BeeMail Newsletter

Xerces Society

Corona® Tools – Podcast episode sponsor and Brand Partner of joegardener.com

Pete and Gerry’s Organic Eggs – Podcast episode sponsor and Brand Partner of joegardener.com

About Joe Lamp'l

Joe Lamp’l is the creator and “joe” behind joe gardener®. His lifetime passion and devotion to all things horticulture has led him to a long-time career as one of the country’s most recognized and trusted personalities in organic gardening and sustainability. That is most evident in his role as host and creator of Emmy Award-winning Growing a Greener World®, a national green-living lifestyle series on PBS currently broadcasting in its tenth season. When he’s not working in his large, raised bed vegetable garden, he’s likely planting or digging something up, or spending time with his family on their organic farm just north of Atlanta, GA.

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