Rain Garden Attracts New Species at Risk Bumble Bee

By Brittany Killingbeck, Species at Risk Assistant, Royal Botanical Gardens.

In the RBG Arboretum you will find a lovely rain garden nestled next to the Rasberry House parking lot. This rain garden was designed in 2019 by RBG’s Aquatic Ecologist, Jennifer Bowman to collect runoff from the paved parking lot, preventing erosion and filtering pollutants. It also doubles as excellent pollinator habitat, with several dozen species of native grasses and wildflowers blooming across the growing season.

In the summer months, RBG staff enjoy sitting outside during lunch to watch the butterflies and bees forage on native wildflowers in the rain garden. I personally love chasing the different bumble bees around with my phone camera, trying to catch their ‘good side’ for identification features. Often these features are only recognizable to a well-trained eye, so I upload my photos to iNaturalist so that experts from around the world can identify the bees.

Lo and behold, there was a hidden gem among my photographed specimens. Drum roll please… a Yellow-banded Bumble Bee (Bombus terricola), the first record of this Species at Risk at RBG!

Yellow-banded Bumble Bee (Bombus terricola)

The Yellow-banded Bumble Bee is listed provincially (2016) and federally (2018) as a species of ‘Special Concern’, meaning that while it is not yet threatened or endangered, it may become so in the future. It is a habitat and forage generalist that lives in mixed woodlands, meadows, grasslands, farm fields, and urban areas. In other words, it needs habitats with high plant density and diversity. The rain garden contains over two dozen native perennial plant species, and the surrounding natural areas provide several habitat options – perfect for this bumble bee!

Unfortunately, most bumble bee species are experiencing declines in their populations. The major threats to bumble bees, and insects in general, include:

• habitat destruction and fragmentation,
• pesticides,
• invasive species,
• pests and diseases, and
• climate change.

It is likely a combination of these factors causing population declines. Perhaps losing a single species of bumble bee doesn’t seem concerning to some, but the impacts are not limited to just that species. Bumble bees are excellent pollinators, and generalists like the Yellow-banded Bumble Bee pollinate a wide array of plant species during their lifetime. Those pollinated plants go on to reproduce, providing food and shelter to other creatures, which in turn creates a healthy, diverse and complex ecosystem.

How Can You Help Bumble Bees?

As you can see, even the smallest efforts like a rain garden can have an impact. Here are some quick, easy changes you can make to your garden to help bumble bees and other pollinators.

1. PLANT NATIVE SPECIES! Our native insects need native species to forage on and use as habitat. Plant a variety of species so there are blooms across the seasons (early spring to late fall). Choosing your plants according to your light conditions and soil type can help ensure a lower-maintenance flower bed. All our rain garden plants (moisture-loving plants in the middle, drought-tolerant species all around the rim) have flourished without being provided any additional watering.

2. Leave the yard messy. No, I’m not referring to the kids’ toys or patio chairs; leave old flower stems, broken branches, and bare patches of soil to create habitat. Bumble bees typically nest underground or in decomposing logs, and queens need hibernation sites for the winter.

Here is a list of some of the plants in our Rasberry House garden beds, in case you need ideas to get you started for your own pollinator garden or rain garden:

Moisture-loving, sun-loving plants:

– Blue Flag iris (Iris versicolor)

– Blue Vervain (Verbena hastata)

– Boneset (Eupatorium perfoliatum)

– Cardinal Flower (Lobelia cardinalis)

– Fox Sedge (Carex vulpinoides)

– Soft Rush (Juncus effusus)

– Spotted Joe-Pye Weed (Eutrochium purpureum)

– Swamp Milkweed (Asclepias incarnata)

– Turtlehead (Chelone glabra)

Drought-tolerant perennials:

Spring-blooming:

– Canadian Columbine (Aquilegia canadensis)

– Virginia Strawberry (Fragaria virginiana)

– Foxglove Beardtongue (Penstemon digitalis)

– Hairy Beardtongue (Penstemon hirsutus)

Summer-blooming:

– Black-eyed Susan (Rudbeckia hirta)

– Butterfly Milkweed (Asclepias tuberosa)

– Common Milkweed (Asclepias syriaca)

– Cylindric Blazing Star (Liatris cylindracea)

– Dense Blazing Star (Liatris spicata)

– Nodding Wild Onion (Allium cernuum)

– Pearly Everlasting (Anaphalis margaritacea)

– Upland White Aster (Solidago ptarmicoides)

– Virginia Mountain Mint (Pycnanthemum virginianum)

– Wild Bergamot (Monarda fistulosa)

Fall-blooming:

– Flat-topped or Grass-leaved Goldenrod (Euthamia graminifolia)

– New England Aster (Symphyotrichum novae-angliae)

– Smooth Blue Aster (Symphyotrichum laeve)

Grasses

– Big Bluestem (Andropogon gerardii)

– Canada Wild Rye (Elymus canadensis)

– Little Bluestem (Schizachyrium scoparium)

– Switchgrass (Panicum virgatum)

– Virginia Wild Rye (Elymus virginicus)

Shrubs

– Canada Plum (Prunus nigra)

– Elderberry (Sambucus canadensis)

– New Jersey Tea (Ceanothus americanus)

– Winterberry (Ilex verticillata)