A few weeks ago, I noticed the tell-tale sign that leafcutter bees are at work in the garden — tidy oval and circular holes in leaves.

These solitary bees create cavity nests by shaping oval pieces of leaves into tunnels. The finished nests look a lot like green cigars. Smaller circular pieces are used to divide the nest into cells (rooms) for each larvae, or to cap the end of the nest. This Wild Pollinator Partners blog post about Leafcutter bees includes a picture of nests found under a rock.

In our garden, they really like to use leaves from fireweed and rosa glauca. In Bees: An Identification and Native Plant Forage Guide (at Ottawa Public Library), Heather Holm lists other common plants that leafcutter bees use for nesting materials: tick trefoil, St. John’s wort, ash trees, and redbud trees. Over the past couple of years, I found that leafcutter bees used a wide variety of leaves around the yard.

Within each brood cell, a female leafcutter bee makes a ball of pollen, called bee bread. She then lays an egg on top of the bee bread, and closes up the brood cell. When the bee larvae hatches from its egg, it eats the bee bread as it grows. The larvae then forms a cocoon where it develops into a bee.

I’ve managed to catch a few leafcutter bees cutting pieces from the fireweed leaves (Youtube video). They are amazingly quick at cutting each leaf piece. Sometimes they stop cutting part way and abandon it, perhaps because the leaf is too tough. Once they finish cutting a leaf piece, they struggle to carry the extra weight. I often see them stopping to rest, with the leaf piece still in their mandibles, on their way back to the nest.

Despite comparing my photos of leafcutter bees with those in identification guides and web sites, I am not sure what kind of leafcutter bees are living in our yard. My bee identification skills have a long way to go.

Nest sites

Both this year and last, leafcutter bees have been making nests between rocks in the dry-stone walls of our terraced garden. Here’s a video of a leafcutter bee returning to its nest, and then leaving again. Since the bee isn’t carrying a leaf piece, it is provisioning the nest with a load of pollen, which you can see on her underside. There are at least three bees currently nesting in our rock walls. I’ve read that they like nesting near each other.

In 2017, we watched leafcutter bees making nests in the frames of our metal lawn chairs. Sometimes they had trouble getting into their nest entrances with the big leaf pieces, so we cheered them on, and were relieved when they finally succeeded. Now, our main seating area is located next to the stone walls where the leafcutters are nesting, so we again have a front-row seat to watch their activity. Such fun to watch!

Leafcutter bees will also use artificial bee boxes. If you do choose to place a bee box in your garden, make sure to line the tubes with paper that can be replaced every 1 or 2 years. This simple stem will help reduce the spread of parasites and fungal diseases between adjacent nest sites. For more information on bee box maintenance, see The horrors of mass-produced bee houses.

Foraging

Leafcutter bees are relatively easy to spot on flowers because they tip the end of their abdomen up in the air. They also carry pollen on hairs underneath their abdomen, instead of on their back legs.

I usually find them on flat, open flowers with a daisy-type shape. According to Holm, leafcutter bees are generalist foragers and will gather nectar and pollen from a wide variety of flowers.

A mysterious, lurking bee

As I watched the leafcutter bees coming and going from their nests, I spotted a smaller bee hanging out nearby. At first, I thought it might be a male looking to mate.

Then, I noticed that the bee had a very pointed abdomen. Uh-oh, I recognize that shape from pictures of parasitoid cuckoo bees. I didn’t have my phone, so I have no photo of the bee, but I believe it was a Modest Cuckoo Leafcutter Bee (see BugGuide). As usual, wherever there are bees, there are other insects that prey upon them, one way or the other.

I parked myself near a nest, with a cup of coffee, waited and watched. Sure enough, once the leafcutter bee flew away, the cuckoo bee entered the nest to lay its eggs. The pointed tip of the cuckoo bee’s abdomen is used to pierce the pollen ball to insert, and hide, its own eggs. When the cuckoo bee eggs hatch, they will eat the leafcutter larvae and the pollen that was left for them. For more on cuckoo bees, see the Restoring the Landscape page Native Bee Spotlight: Cuckoo Bees – Coelioxys spp. I’m wish this didn’t happen to ‘my’ leafcutter bees, but I know it is just how nature works.

When I began learning about native bees two years ago, I was delighted to find the PDF book, Bees of Toronto. There aren’t many Ontario-specific resources, let alone ones from Ottawa. Now we’re lucky to have the Wild Pollinator Partners blog posts and events that highlight native bees in our area.

After reading Bees of Toronto, two things stuck with me:

• the forward is written by Margaret Atwood, whose father was an entomologist. As an Atwood fan, I am pleased that in addition to knitting, we also share an interest in pollinator gardening.
• Toronto has an (un)official bee, bicoloured Agapostemon, that lives in subterranean ‘apartment buildings’; while females each have their own ground nest networks, they share an entrance. This shared entrance allows bees to take turns guarding it from intruders, while their neighbours are out foraging.

For more on Toronto’s efforts to create good, urban habitat for pollinators, listen to the PolliNation Podcast interview with Scott MacIvor. I hope these unique pollinator initiatives survive the Ford government, which is degrading Ontario’s protections of wild spaces and wildlife, and is targeting Toronto’s progressive ways.

Meet the Ottawa relatives

This week, while I was supposed to be weeding the garden for upcoming tours, I came across a peculiar ground nest beside the driveway. I have never seen anything like it before, and I immediately worried that I had ground-nesting wasps next to a busy walkway. The nest is conical with two ‘chimneys’. After some research, I concluded the structure didn’t look like as wasp nest.

I camped out on the uncomfortable asphalt to observe. The weeds could wait because I had more important investigative work to do. Whatever was in there would appear, but pop down out of sight whenever I got close. Strangely, and a bit disturbingly, smart.

After I was still, they began flying out — five of them in total. Here’s a brief Youtube video of them exiting the nest. I could see pollen on their legs, which confirmed that they’re bees (vegetarian) and not wasps (which eat other insects, and nectar). Also, they’re a very pretty green on top, with striped abdomens. Aha! They are bicoloured Agapostemon, also known as green sweat bees.

I have seen green sweat bees go into ground nests before, but only singly. The nests were just holes in the ground, never into such a strange-looking structure. I wonder if the conical shape of the nest indicates that there are a lot of females excavating below. I also wonder if they would all be sisters, or if any female green sweat bee in the vacinity could move in.

If you have a sharp eye, you can see one of the reasons the green sweat bees are on guard. Sitting on a leaf in the lower-right, you’ll see a kleptoparasitic bee lurking, waiting for an opportunity to invade their nest to lay its own eggs.

Green sweat bee flower favourites

Well, the next question was: where were they finding all this pollen? They were making quick trips with significant pollen loads on their back legs. After looking all around the front and back gardens, and my neighbours garden, I found green sweat bees on prairie cinquefoil growing nearby. I grew this from seed last year and have never seen it bloom before. The flowers look a lot like strawberry flowers.

In Bumblebee Economics, Berndt Heinrich chose prairie cinquefoil as one of the plants for tracking pollen-collection visits of different bumblebee species (page 154). Other flowers included wild carrot (non-native), St. John’s wort, pond lily, and wild rose. I figured that these plants must be good pollen-producers, so I added them to my garden. The wild carrot (Queen Anne’s lace) was already in my yard and has been hard to eliminate because it self-seeds so prolifically.

From previous years, I know that green sweat bees also really like red pincushion flower (Knautia macedonica). This plant short-lived but self-seeds moderately, so there are lots of flowers around. I’ve grown red pincushion flower for years because it blooms for months, and I like the dark red colour of the flower buttons.

Like I always say, you never know what you’ll see in the garden. Back to weeding.

Oh, wait — there are the Chickadee parents with their 5 babies. I can’t miss watching that. The weeding can wait, again.

On June 11th, I first spotted a worker bumblebee in our yard. Worker bumblebees been slow to increase in numbers. Even though it’s now two weeks later, I still only see 2 or 3 workers at a time. My husband reminded me that I worry about the lack of bumblebees every year.

Queen bumblebees emerge first early in spring from their underground overwintering spots to fatten up and start nests. When the queens have gathered enough pollen and nectar, they lay eggs. While the larvae develop, the queens will still forage as needed. Once the first brood emerges, new workers assume the foraging duties. The queen will then only leave the nest if she needs to help collect pollen and nectar. Once there are enough workers to forage, the queen will remain in the nest for the rest of the summer/the rest of her life. For more about bumblebees’ lifecycle, see my page Helping Bumblebees.

I am still seeing queen bumblebees alongside workers. I am also still seeing queen bumblebees looking for nest sites. You can tell whether a bumblebee is a queen or a worker by its size; queen bumblebees are significantly larger. The size of workers varies depending on the quality and amount of food they had, and the temperature, during development.

So far, worker bumblebees have primarily been foraging on virginia waterleaf, pagoda dogwood, penstemons (beardtongue), figwort, as well as catmint and ‘May Night’ salvia.

Special queen bumblebee

The queens and workers I have seen in the garden have all been Common Eastern bumblebees. That is, until June 16th when I saw a Northern Amber bumblebee queen visiting hairy beardtongue flowers. Isn’t she pretty?

Each morning, she visits the hairy beardtongue flowers. When she leaves, she goes up into the cedar hedge, for shelter I assume. I have never noticed a bumblebee do this before. She doesn’t venture anywhere else in the yard.

I hope she continues to visit now that the male European wool carder bees are out. They are know as ‘bully bees’ at our house because they are territorial, and will hit and chase other bees away from the flower patch they’re guarding. I even saw two males rolling around on the ground fighting. No sign of the smaller females yet.

Northern Amber bumblebees like to forage on vetches, clovers, prunella (self-heal), eupatorium (Joe Pye, boneset), comfrey, and asters. Last year, I planted Canada milk vetch and several other leguminous plants, Joe Pye weed, boneset, asters, and self-heal grows in our lawn. This year, I am also trying annual borage, which is related to the aggressive, perennial comfrey. I hope she likes our food options and finds a nest site in or nearby our yard.

The Northern Amber bumblebee is often confused with the Golden Northern bumblebee. Northern Ambers are distinguished by their yellow facial hair that can be seen in this blurry fly-by photo. For more information, see the Discovery Life page for Bombus borealis.

There have been a lot of babies in the garden this week.

Fledgling birds

For a few days, we’ve heard very noisy baby birds begging for food. While we couldn’t see them, we suspected they were Chipping Sparrows. We finally saw the young birds out in the open sitting on branches and hopping around the ground between plants. The frantic parents make trips back-and-forth from the feeder to deliver seeds. Each time the mother or father bird approaches, the fledglings frantically flap their wings and squawk; they are loud and we hear them begging constantly from dawn to dusk.

We finally found out why there is so much noise — there are also two fledgling Cardinals. They are adorably round and fluffy. They also raise a ruckus whenever their parents are near; they tremble, flap, and make plaintive begging sounds. While they wait patiently for their next meal, the little Cardinals sit quietly, walk around a bit on their branches, and frequently stretch their wings.

Perhaps the Cardinals are younger than the Chipping Sparrows because the Cardinal parents aren’t feeding them seeds. They must still be eating soft insects, like caterpillars, found in nearby trees or on the ground.

American Lady butterfly caterpillars

Since I saw the American Lady butterfly laying eggs on our pearly everlasting, I’ve been watching for caterpillars. They’ve hatched! To locate them, I look for webbed areas and frass (caterpillar poop). The caterpillars create little webbed shelters so they can hide from predators, like parents of baby birds. There are caterpillars on all the patches of pearly everlasting in the front and back. Interestingly, this year there are no eggs on the field pussytoes, another American Lady host plant. (Edited: I later found some on field pussytoes.)

Since warmer weather arrived here in Ottawa at the end of May, there’s been a lot more pollinator activity in my garden. I’ve observed ground and cavity nesting bees, queen bumblebees, and a few butterflies.

Inconvenient (for me) ground nests

I’ve spotted lots of bees going into ground nests all over the front and back gardens. The entrances can go unnoticed, unless you see a bee going in. More often than not, they’re located right next to plants or under dry leaves. There is a clear preference for sloped areas that are south- or west-facing.

Usually I see a bee arrive, and disappear into an invisible hole in the ground, just as I reach to dig up a plant, clear leaves, or pull weeds. Now, I don’t want to work in those areas to avoid damaging nests, or destroying entrances. I have mistakenly done in the past. It’s sad to watch a bee laden with pollen searching for a nest entrance that’s gone, or that it can’t find because I removed the weeds or leaves it used as landmarks.

Oh well, I guess will just have to skip those chores. A messy garden is better for pollinators, anyway. Now I have more time for bee-watching.

Lurking parasitoids

This spring, I noticed two different kinds of insects hovering and zig-zagging close to the ground looking for nests to prey upon. One of them was the odd bee-fly that is furry like a bee, and has a long ‘beak’ for drinking nectar. Females fling their eggs near ground nest entrances. The eggs will then stick to bees as they enter their nests. When the eggs hatch, the bee-fly larvae consume the bee larvae.

I also think I’ve seen a few kleptoparasitic cuckoo bees that have distinctive hairless, red abdomens. (I’m using a picture of a nomadic cuckoo bee on Heather Holm’s Instagram page to tentatively identify the bee, from memory.) Cuckoo bees enter ground nests of other bees to lay their eggs. Once the eggs hatch, the larvae eat pollen left for the original ground-nests’ residents.

It seems like bees abandon nests if they spot parasitoids/kleptoparasitoids nearby. I stopped seeing bee activity in several locations after I had spotted the cuckoo bee flying in the vicinity.

Cavity nests

The only cavity-nests I’ve found so far are for small carpenter bees. In the backyard, they’ve been digging nests in last year’s ironweed stems.

I think I’ve seen mason bees on crabapple flowers and Virginia waterleaf flowers. I wonder where they’re nesting? Perhaps they’re using the cup plant stems I left for them; I cut the stems off about 15 inches from the ground, and added the top part of the stems to a brush pile.

Bumblebee nest

I’m pleased that a queen bumblebee has chosen to make a nest in our yard. A first for us! It is under our shed in a former groundhog den that was later used as a mouse nest. Unfortunately, it is too close to the shed door for my liking, so the area is now fenced off.

We’ve watched numerous bumblebee queens searching around the backyard, especially the perimeter, for nest sites. Almost all of them check out the chipmunk den entrances in our terraced garden. They hover close to the ground, flying back and forth, going under leaves and under rocks, and then coming out again. Here’s a Youtube video I found, called Bumblebee Queen in Search of Potential Nest Locations, that shows the searching flight pattern bumblebee queens use to find nest sites.

Butterfly visitors

We’ve had a few butterflies visiting the garden, usually American Ladies and Red Admirals. (BugGuide has a handy picture for distinguishing American Lady and Painted Lady butterflies.) Other types passed through too quickly for me to photograph or positively identify.

While the calendar was turned to May last month, it felt more like March in Ottawa. The miserable, cool weather limited pollinator activity in the garden, slowed plants emerging from the ground, delayed blooms, and prevented seed germination.

Temperature and pollinator activity

Throughout the month, local gardeners shared my concerns about the dearth of pollinators. One gardener pollinated his apple trees with cotton swabs — just in case. Another wondered if there will be fewer berries for birds on native shrubs this year. And another questioned whether the milkweed would pop up before Monarchs arrived to lay eggs on it?

Last year, I learned that excessive heat harms bees. When the temperature hovered around 40°C last summer, I noticed only a few honey bees in the garden. How urban heat affects bee populations summarizes how high temperatures affect native bees.

On the flip side, what is the impact of cooler than normal temperatures? How warm does it needs to be for native bees to become active? The University of Maine Extension article, Understanding Native Bees, the Great Pollinators: Enhancing Their Habitat in Maine, states:

“The most likely place to find bees is in the flowers of native plants, when the day is sunny, relatively calm, and the temperature is above 70°F. To be active, fly and feed, bees need to be warm. A few species are active below 60°, but most prefer temperatures above 72°. Wind makes flying more difficult because it requires more energy.”

In Celsius, that means it needs to be at least 15.5°C for the more cold-hardy bees, and 22°C for the rest. According to the Weather Network records for May 2019, there were 16 days above 15.5, and only 2 above 22. Not very good weather for native bees. It doesn’t seem that the weather was favourable for honey bees either because I saw only one in my garden this month.

In Bumblebee Economics (at Ottawa Public Library), Bernd Heinrich explains that bumblebees are more tolerant of cooler weather because they can shiver to warm up. I did frequently see queen bumblebees foraging and looking for nest sites in my yard. It will take several weeks, after these queens choose nest locations and lay eggs, before the first brood of workers will be out and about.

Luckily, bees aren’t the only pollinators. Flower flies are also more tolerant of cooler temperatures. I did spot some in the garden, so hopefully they picked up some of the slack.

Most popular flowers

In May, the popular flowers for queen bumblebees were on my ‘PJM’ rhododendron, long-blooming lungwort, and crabapples. The bumblebees liked the flowers so much that they even visited them after they had dropped onto the ground. While I was watching, to my surprise, the queen bumblebees ignored my native perennials, shrubs, and trees.

For smaller native bees and other pollinators, the winners were serviceberries, crabapples, and wild strawberries. It looked like some native bees were nesting under the plentiful strawberry plants that I use as ‘living mulch’ in my hedgerow. Perhaps they preferred foraging close to their nests instead of flying up to the shrubs and trees.

May 2019 trees and shrubs in bloom

May 2019 flowers

A few notes about my monthly tables

As I made May’s tables, I thought of a few points worth mentioning here.

For many plants, I have multiple clumps in the front and back yards, and in differing degrees of sun. The plants in more sun bloom earlier that ones in more shade, which prolongs bloom times in the tables.

If plants have no pollinator value, should I bother including them? I’m going to include them in the tables anyway because I have been surprised to see pollinators visiting ‘worthless’ flowers. A few weeks ago, my son pointed out a queen bumblebee drinking nectar from periwinkle flowers. It wasn’t visiting the Merrybells, Dutchman’s breeches, or Hellebores in bloom. Maybe my patches of those native plants are still too small for them to notice.

I want to start tracking what’s going on in my front and back gardens. This information will help me ensure there’s always something in bloom for pollinators. It will also be useful for planning future changes to my garden beds. My table format is a simplified version of the Minnesota Wildflowers What’s Blooming pages.

Phenology

Have you ever heard of phenology? I hadn’t either. It basically means what happens when in nature. There’s a lot of interest in phenology now as scientists track how climate change is affecting the timing of plant and animal activity. Unfortunately, the shifts in timing are not always in sync.

I plan to participate in PlantWatch, a community science project collecting flowering dates for selected plant species. This data will be used by researchers studying climate change in Canada. Although I only have 7 of the 22 species they’re tracking, I’ll contribute what I can.

April flowers

April 2019 was quite cold and rainy. It seemed to drag on forever. Earth Day, April 22nd, fell on Easter Monday, so we all had the day off. It turned out to be the warmest day of the month, and a perfect time to watch the first bees and butterflies in our yard.

Pussy willow catkins, bulbs, and spring ephemerals appeared on cue. The pussy willow shrubs were the star attraction for pollinators. Here’s a video of the tremendous pollinator activity on my largest pussy willow; there are mining and cellophane bees, flower flies, and a few honey bees. Oddly, I have never seen a single bee on my hepatica or bloodroot.

April pollinators

I saw the first bees, and only butterflies, on Earth Day, April 22nd.

I have a lot of trouble identifying bees. My guesses for these two are based on articles on Houzz by bee expert, Heather Holm: Invite Cellophane Bees to Your Garden by Providing Patches of Bare Soil and Invite Mining Bees to Your Garden by Planting their Favourite Plants.

Work to do

It turns out that two of my earliest spring flowers are invasive, or nearly so — squill and periwinkle. The squill is easy to remove, but periwinkle is more challenging.

I actually moved squill bulbs to my pollinator garden because I thought squill and bloodroot made such a pretty combination. While it may not be on an official invasive species list for Ontario, it has spread a lot in wild spaces. Here’s an interesting article, Is Scilla siberica invasive? about squill and how plants are deemed ‘invasive’. I had an inkling that it might be after I saw a large, dense patch of it in a clearing at Mud Lake. I’m not sure what I can substitute it with that will bloom so early, at the same time as bloodroot. I’ll have to take a walk around the neighbourhood to see what other bulbs are blooming now. For ideas, I will also consult the PDF booklet Grow Me Instead, and this list of Alternative Plants for Invasive Species. These suggestions don’t always bloom at the same time though, so they won’t provide a similar flower combination.

Periwinkle is considered invasive according to Ontario’s Invading Species Awareness Program. I have successfully removed periwinkle in another part of my garden. While pulling it out, I carefully teased out the root clumps. Whenever it popped up afterward, I pinched it off. At least it is easy to spot since most other plants aren’t up yet. I will always have to battle periwinkle though because a neighbour grows it willingly.