Native bees like this one, Augochlora pura, shouldn't be confused with honeybees. Most don't produce honey, but they are crucial for pollination. (Photo: Sam Droege’s USGS Bee Inventory and Monitoring Lab)
Think fast, home gardeners. How would you handle this scenario? When you prune dead portions of stems, do you bury them in a compost pile with other lawn and garden debris or put them in lawn bags to be hauled away?
If you're like most gardeners, you likely do the latter. And you'd be wrong.
That’s because females of a host of native bees like the small native carpenter bee that lives in eastern North America, Ceratina calcarata, hollow out dead areas of pithy stems and turn the canes into long tubes in which they lay their eggs. The eggs hatch in late summer, but the bees stay in the stem during the winter even after growing into adults, emerging sometime in the spring. If you discard the stems in which this process is taking place, you’re doing far more than killing the bees and destroying their happy home; you’re decreasing the number of pollinators for your garden.
"What I do is find some out-of-the-way corner where I don’t have to look at the canes that much, tuck them in there and the bees can emerge at the appropriate time," said Paige Embry, author of "Our Native Bees, North America’s Endangered Pollinators and the Fight to Save Them" (Timber Press, 2018). "There may be more than one kind of bee nesting in those canes, so the times they leave the stem may be staggered," she added. Some examples of plants with pithy canes that tend to be hollow or partly hollow include edible berries such as raspberries or elderberries, Embry said.
That's just one of the easy things people can do to help native bees and one of the many useful as well as fun facts about some of the 4,000 native bees in the United States that Embry includes in her book. The idea to write the book started with a citizen science project in which participants wanted to know if yields in people’s gardens were limited by a shortage of native pollinators. "The people conducting the project were only interested in native pollinators, so they decided to study tomatoes because honey bees can’t pollinate tomatoes," recalled Embry.
She calls that her "holy smokes moment" because she didn’t know at the time that honey bees can’t pollinate tomatoes.
"I became filled with a zeal to tell everybody about native bees when I had that epiphany," said Embry, a long-time gardener who writes about bees, gardening and agriculture for Horticulture, The American Gardener, Scientific American, the Food and Environmental Reporting Network and others.
Who else doesn't know this?
A native bee, in this case a bumble bee, visits a greenhouse tomato. It was the realization that honey bees cannot pollinate tomatoes that led Paige Embry to write her book, 'Our Native Bees.' (Photo: Clay Bol)
"I had been a gardener for decades, gone to school, studied horticulture, had a garden design business and taught gardening classes, so I considered myself a pretty-well educated gardener," said Embry. "And then I learned that honey bees can’t pollinate tomatoes. Honey bees aren’t native to North America, which I had known, but a host of bees that are native to North America can pollinate tomatoes. I don’t know why it was such an epiphany for me, but it was because it seemed like it was something I should have known with all my shelves full of gardening books.
"So, I started asking some other people who were also well-educated gardeners, and most of them didn’t know honeybees can’t pollinate tomatoes, either. What happens is that with most flowers, you will see the pollen right out on the anthers. But with tomatoes — and a not insignificant number of other plants — the pollen is hidden inside the anthers and has to be shaken out of tiny little holes in the anthers."
Getting the pollen out of the anthers requires a process that Embry compares to shaking salt from a salt shaker. With bees, this is called buzz pollination. A bumble bee, she added, is the great classic tomato pollinator. "What they do, is they grab hold of the pointy part of a tomato flower with their mouth parts and they curl their body around the end of the flower. Then they vibrate their wing muscles at a specific frequency and that shakes the pollen out of the anthers. You can do the same sort of thing with a tuning fork! Honey bees just don’t know how to do that."
There are so many stories like this one, and here's another.
The first offspring (left) of a small native carpenter bee, Certina calcarata, is always small and is known as the dwarf eldest daughter. She also has earned the nickname Cinderella because her larger mother (right) pushes her out of the nest in the winter and makes her collect food for her brothers and sisters. (Photo: Sandra Rehan/University of New Hampshire)
Ceratina calcarata is unlike many native bees, which are frequently called solitary bees because they lay eggs in individual nests and then abandon them as opposed to living in a colony in a hive. This little bee lives in the stem with her offspring and the pollen and nectar she has collected for them to survive the winter. "But when the bees reach adulthood, they need more food," explains Embry. "So, the mama bee goes out to get them more food, but she doesn’t go alone. What happens is that the very first little pollen wad she put in the stem was a very small one. How big a bee is going to become as an adult depends on how much food it had to eat as it was growing. So, this first bee is called the dwarf eldest daughter, and the mama bee forces the dwarf eldest daughter to go out and help her collect food for her brothers and sisters."
If, about now, this story is starting to sound like a certain favorite childhood fairy tale about a mean stepmother and cruel siblings, you’re getting the picture. Sadly, however, there will be no fairy godmother to save this little bee, and she will never meet her Prince Charming. "Because the dwarf eldest daughter was born small and does this work, she has no hope of surviving the winter and having any offspring of her own," says Embry. "So, somebody nicknamed that bee … Cinderella."
Embry’s book is filled with fascinating facts like this about America's native bees. She gained that information through a multi-year obsession with native bees that has taken her on travels from her home in Seattle to farms and fields from Maine to Arizona where she visited and interviewed farmers, gardeners, scientists and bee experts of various stripes while researching her book.
Understanding native bees
As she was researching the book, Embry kept coming across bits and pieces of information that convinced her most people don’t have a very good understanding of our native bees. She said most people envision a bee as generally one of two things: "It’s either a honey bee or it’s something with a striped bottom that stings you. Those are both wrong. Bees are so much more than that!"
For one thing, she points out, many wasps have striped bottoms and sting you. Wasps, of course, aren’t bees at all. "A lot of bees don’t have striped bottoms and a lot of bees don’t sting," she said. "No male bee can sting you. Male bees don’t sting because a stinger is modified for a female’s reproductive parts. So, the guys don’t have stingers!"
Augochlorella aurata is a type of sweat bee — aptly named because of its attraction to human perspiration. (Photo: USGS Bee Inventory and Monitoring Lab/Flickr)
Another thing she learned is the great diversity in size and color that exists among native bees. Some are even smaller than a grain of rice, she said "And some of them are shiny and purple or shiny and green and there are these beautiful little bees that are so teeny weeny that to appreciate them you have to look at them through a microscope." When you do that, she said, you realize they look like they are made of what looks like black-and-yellow enamel. "Some of them were just surprisingly beautiful creatures!"
Another lesson Embry shares in the book is that most native bees don’t live in colonies in a hive like honey bees, which are called social bees for this reason. While there are a few native bees that are social bees, such as bumble bees, these colonies only last for a season. At the end of the year when the weather turns cold, these bees die except for next year’s queens-to-be. They find themselves a little hole somewhere and sleep out the winter before starting new colonies in the spring.
Most native bees are called solitary bees because they live their entire lives alone, said Embry. "They will emerge at certain time of year depending on the kind of bee, the males and females mate and then the males generally die because male bees are really just about mating and then females will start their work. They will gather pollen and nectar and they will put it in a hole above ground like a beetle burrow or a below ground hole. And they gather enough pollen and nectar to grow one bee from egg to adult. Then they lay an egg on that pollen and nectar wad and they close off that hole and, in most cases, they never see their offspring."
Native bees and global food supplies
One of the things that Embry wondered about as she learned more about the role native bees play in pollination was what would happen to global food supplies if all the world’s honey bees suddenly up and died. If that were to happen she wondered, "could the wild bees take over or would we be out pollinating apples with our toothbrushes?" The answer was more complicated than she thought.
"There was a study that looked at global food crops and their dependence on pollinators. Researchers found that 87 crops needed or used animals to pollinate them. But how badly those crops needed the animals varied a lot more than I would have thought. Some plants couldn’t produce fruit without the animals to cart the pollen back and forth. A lot of the others could, but just not as effectively. It’s not like some plants would necessarily disappear, but if the farmers are going to be able to make a living they’ve got to be able to get a crop. And the pollinators really help with that."
The study raised several other questions in Embry’s mind about what would happen if the world began losing bees for pollination. How much more land would have to put into production? How much more would production cost? What would that do to the cost of our food?
"The impacts of pollinator shortage were more complicated than I thought they would be when I first started on this," she concluded.
Tips for home gardeners
It's tough to think about these big-picture concerns, but there are things home gardeners can do to help attract native bees to their landscapes and to help them thrive once they're there. Embry suggests focusing on three things.
- One is pesticides. Avoid them she said. "That will make their life a lot easier."
- The second is plants. "I wish that I had like a go-to plant that was a great plant for everywhere, but it varies a lot from place to place." Instead, she said to plant what the bees are attracted to in your area. To discover what those pollinator plants are, Embry suggests several simple things. One is to take a walk on a day when it's hotter than 55 degrees and there's not much wind and you can see which plants are blooming and attracting bees. Another is to plant a garden that has things blooming in all seasons, native plants as well as non-natives. Some native bees, she pointed out, will be active even while there's still snow on the ground. Another is to choose plants that flower at all heights, from ground-hugging flowers to tall trees. "I’ve seen newly emerged queen bumble bees in crocuses," she said. "There are bees that like to use willows and maples." It’s important to remember, she added, that while many bees are specialists that will only go to a certain group of plants like members of the aster or legume families, there are many other species of bees there are generalists, and they will feed their babies pollen from a whole variety of plants. "I know in California there was somebody who had found 50-plus species of bees on Provence lavender which is not native, but the bees loved it! That again sort of argues for the look-around and see what the bees are loving in your area."
- The third thing is nesting spots. "One of the key things I think people can do is focus on nest spots within flying distance of the flowers," said Embry. "The really little bees — the ones that are smaller than a grain of rice — may only fly a few hundred yards from their nests to the flowers." Solitary bees nest in cavities in the ground that rodents or other critters have dug or that they dig or in holes in logs, stems or other objects above ground. "A lot people want to mulch everything to keep the weeds down, but that can be really hard for the bees who are trying to dig holes in the ground." To emphasize her point, Embry said 70 percent of bees nest in the ground. That’s also something to think about when you might have the urge to fill in the holes the chipmunks create. For the above-ground nesters, a fun project would be to build a bee nesting box. This can be as simple as drilling varying size holes in a 4x4 piece of wood and mounting it on a post.
If people come away from the book with less of a fear of bees and a commitment to bee conservation, Embry will feel like she accomplished her goal. "There is this incredible array of bees, and most of them don’t sting, so you don’t need to be fearful of them," she said. The conservation piece is especially important to her.
"Bee conservation is the kind of conservation that is incredibly satisfying because you can give money to groups that help a whole variety of animal or plants or the environment and that’s good, but you often don’t know exactly what your money is achieving. You hope for the best. But when you plant good pollen and nectar plants, you stop using pesticides or you save some of those stems, you will almost certainly see the bees. Once you start looking, you’ll see that a there are a whole variety of bees that are showing up."
This happened to Embry when she planted coreopsis by her walkway last year. "The whole summer it just made me smile because I would walk past them and I would look and there was almost always some bee on that coreopsis. It was there because instead of choosing a plant for its foliage, I deliberately chose a plant I knew was a good pollinator plant. And the bees came."
Looking for more info?
Here are several resources to help you identify bees you might see in your yard or on a walk.
- If you have a bee photo and want a sense of the range of the bee, look for it on the Discover Life website.
- The U.S. Geological Survey's website for bees and the associated image account on flickr for the Bee Inventory and Monitoring Lab.