Pollinator-friendly Perennials for the Fall Garden

By Colleen Zacharias, Master Gardener

The signs are all around us. The shrinking populations of insects the world over is due to the effects of climate change and loss of habitat. Gardeners can make a difference. A study led by the University of Bristol earlier this year in partnership with the Royal Horticultural Society and the universities of Edinburgh and Reading “measured for the first time how much nectar is produced in urban areas and discovered residential gardens accounted for the vast majority – some 85 percent on average” (Science Daily, February 21, 2021). Interestingly, the study concluded that the nectar supply in private gardens in urban landscapes compared to farmlands and nature reserves comes from a more diverse range of plant species.

Pollinator conservation is top of mind these days. Insects provide food for birds and many other small creatures. Critically important, insects pollinate approximately 75 percent of the crops in the world. Insects also play an important role in soil health as well as in warding off pests.

The plight of the monarch butterfly is familiar to most non-gardeners, including young school-age children, and milkweed is almost a household word. Garden centres across North America over the past few years have seen a surge in demand for Asclepias. Nevertheless, saving the monarch butterfly from drastic decline is also dependent on addressing climate change and reducing the use of pesticides and synthetic fertilizers.

In February 2021, the World Wildlife Fund-Mexico reported a reduction of nearly 26 percent of monarch butterflies overwintering in central Mexico during the winter of 2020-2021 compared to the previous winter. The report also stated there was a 75 percent decline in the winter of 2019-2020 versus 2018-2019. Scientists are also studying the effects of wildfire smoke on the flight patterns of butterflies. Smoke pollution, for example, has been shown to adversely affect the flight patterns of painted lady butterflies.

Another widely publicized insect decline in the past decade is that of bees. But everything will be alright if we just plant more Bee’s Knees petunias or other annual flowers labelled pollinator-friendly, correct? A scientific review published in the journal Biological Conservation in 2019 found that declines in almost all regions around the world may lead to the extinction of 40 percent of insects over the next few decades. One-third of insect species are classified as endangered.(https://www.sciencedirect.com/science/article/abs/pii/S0006320718313636).

As Master Gardeners, we deal in plants and the fundamentals of soils, climate, plant nutrition, organic mulches, and proper watering. For many of us, our gardens, and the immediate community in which we live and volunteer, become our opportunity to make a small difference in the grand scheme of things.

While 2021 has represented one of the more challenging gardening seasons in recent memory for gardeners in southern Manitoba and across the Prairies due to record heat and drought conditions, September is no time for gardeners to call it quits for the year. By growing a diversity of late-season flowering plants, the garden in September and October can play an important role in supporting beneficial insects but also in providing food for birds.

Below are some of my favourite late-season perennials that bring beauty to the garden by providing nectar and pollen. Note, I have taken the liberty of including two ground-cover shrubs. Not all the varieties I have listed are drought-tolerant. In extreme drought conditions, even drought-tolerant plants benefit from supplemental moisture. Drought tolerance, however, is enhanced by building up soil organic matter as well as with the use of groundcover plants and organic mulches.

Actaea simplex ‘Brunette’ (Ranunculaceae family): Formerly known as Cimicifuga; common names include bugbane, snakeroot. Not native to the Prairies. A tall architectural plant for part-shade (I grow Actaea cultivars in different light conditions in my garden and have found that it does best when it receives bright, indirect light). White bottle-brush flowers with pink tints on sturdy stems provide nectar and pollen for bees and a range of other pollinators.

Aconitum carmichaelii ‘Arendsii’ (Ranunculaceae): Common name is azure monkshood. This late-flowering aconitum blooms mid-to late September and October and stands about 3 to 4 ft tall (I find it to be strong-stemmed). The violet-blue hooded flowers are attractive to bees, butterflies, and hummingbirds. An outstanding beauty in the fall garden.

Andropogon gerardii (Poaceae): Common name is big bluestem grass. Native to North America. Stands 3-5.5 ft tall and spreads slowly by rhizomes. Fabulous late season colour (a mix of rusty red-orange-bronze). The distinctive seed heads resemble a turkey foot. Hands down, Calamagrostis x acutiflora ‘Karl Foerster’, feather reed grass, is the most popular (read: overused) ornamental grass today. Plant it beside big bluestem, however, and before spring it soon becomes apparent which grass is favoured more by overwintering birds. ‘Karl Foerster’ has exceptionally showy seed heads which, yes, will attract birds, but typically the wheat-coloured seed heads are still standing by spring, whereas overwintering birds devour the seed heads of big bluestem, stripping them bare well before spring arrives. Big bluestem also provides larval food for butterfly species such as the common wood-nymph.

Anemone tomentosa ‘Robustissima’ (Ranunculaceae): Japanese anemone, common name is windflower. Native to China. This late summer beauty, thankfully, is a spreading perennial by way of creeping underground rhizomes. I have no intention of controlling it in my garden and plan to make way for even more by lifting a section of turf. An abundance of buttercup blooms in September that are attractive to butterflies, although, admittedly, bloom production wanes by about the third week in September. Eminently hardy. Performs best in partial sun.


Anemone tomentosa ‘Robustissima’

Arctostaphylos uva-ursi (Ericaceae): Native to every province in Canada. Commonly known as bearberry or kinnikinnik. A traditional plant used by Indigenous people for food and medicine. Brilliant red berries in late summer provide food for birds such as thrushes, wrens, robins, and waxwings. The berries persist in winter. Dainty, urn-shaped flowers in spring. Bearberry acts as a larval food plant for some butterfly species (brown elfin, freija fritillary, hoary elfin). It is a low growing shrub that forms a dense mat with dark green, glossy boxwood-like leaves. It is a long-lived plant; however, it prefers acidic soil. I add a bit of peat moss and pine needles as well as oak leaves in fall from a volunteer oak seedling.

Celastrus scandens ‘Autumn Revolution’ (Celastraceae): Native to North America. Commonly known as American bittersweet vine. Drought -tolerant once established. Large glossy green foliage; produces showy, waxy, bright orange berries in September that attract birds and provide food and habitat for winter. ‘Autumn Revolution’ has both male and female parts so only one plant is needed. Vigorous grower. Rabbits love it, too. In winter I protect the lower portion of the plant with hardware cloth fencing to deter feeding by rabbits.

Chelone glabra (Plantaginaceae): Native to Manitoba, Ontario, Quebec, Northwest Territories. Commonly known as turtlehead. White two-lipped flowers in late summer. Attracts bumblebees, long horned bees, hummingbirds, and is the only host for Baltimore checkerspot butterfly caterpillars (Manitoba Butterflies: A Field Guide, Simone Hébert Allard, Turnstone Press, 2013). Excellent perennial (height 3 ft) that is bothered by few if any pests or disease.

Chelone lyonii (Plantaginaceae): Native to south-eastern U.S. Commonly known as pink turtlehead. ‘Tiny Tortuga’ turtlehead is outstanding as a low herbaceous hedge (height 15 inches) with fuchsia blooms in early September until frost. The bright fuchsia flower is a two-lipped corolla that might seem to defy entry by pollinators, however, turtlehead is attractive to bumblebees, butterflies, and hummingbirds. Personally, I have not observed butterfly visits to my ‘Tiny Tortuga’ hedge but this outstanding, trouble-free perennial brings late season colour to the part sun-part shade garden.


Cheloni Lyonii ‘Tiny Tortuga’

Cotoneaster horizontalis (Rosaceae): Native to China. Commonly known as rock cotoneaster. This groundcover shrub with small, glossy green leaves spreads very slowly on strong branches in an intriguing, irregular fashion. Brilliant, glossy red berries in September that are eaten by birds. One of my favourites; zone 4; comes back reliably each year with good snow cover as its protection.

Gaillardia aristata (Asteraceae): Native to the Prairies. Gaillardia x grandiflora is hardy to zone 2. Commonly known as blanket flower. A short life span of just 3 to 4 years but reliably self-seeds. Starts blooming in July but with the occasional deadheading, blanket flower will continue to produce blooms to frost. The showy flowers attract a diversity of bees.

Helenium autumnale (Asteraceae): Native to North America. Commonly known as sneezeweed or Helen’s flower. An herbaceous perennial that blooms late August to October. The daisy-like flowers attract bees and butterflies. The seed heads provide food to birds in winter. If Helenium does not overwinter successfully in my garden after a harsh winter, I always replace it with another.

Heliopsis helianthoides var. scarbra (Asteraceae): Native to U.S. and parts of Canada. Commonly known as oxeye or false sunflower. Two recent introductions, ‘Burning Hearts’ and ‘Bleeding Hearts’, provide a floriferous mid-to late summer display with daisy-like blooms on dark stems. Attracts birds and butterflies. Trouble-free.

Ligularia (Asteraceaea): Native to central and eastern Asia. Commonly known as leopard plant although I have never heard local gardeners call it anything other than Ligularia. Loves a moist location but can also be grown in a drier garden so long as it receives full afternoon shade – admittedly, Ligularia’s large leaves will be smaller in a drier, shady situation but impressive, nonetheless. Mine are planted in front of three 50-ft tall evergreen trees, a potentially dry scenario if ever there was one. The soil, however, is humus-rich (annual additions of compost together with a mulch layer of shredded leaves and shredded bark). This year in my garden, the first blooms on Ligularia dentata ‘Britt Marie Crawford’ appeared on August 21. This variety provides an incomparable display of mustard yellow-orange daisy-like flowers throughout the month of September. I also grow Ligularia dentata ‘Desdemona’ which starts its flower show in my garden usually by mid-September.


Ligularia dentata ‘Britt Marie Crawford’ in bloom next to L. dentata ‘Desdemona’ just starting to bloom.

Limonium latifolium (Plumbaginaceae): Native to Romania, Bulgaria, and Russia. Commonly known as sea lavender. An incredibly beautiful plant in September and October with airy sprays of tiny blue flowers on tall, ultra-thin but sturdy stems above a low skirt of broad, leathery evergreen leaves. Attracts butterflies and hummingbirds.

Rudbeckia laciniata (Asteraceae): Native to most of Canada. Commonly known as tall coneflower. A food host for silvery checkerspot butterfly caterpillars. Also attractive to bees. The best bloom display is in August to early September, after which the showy, prominent cones attract birds who feed on the seeds. Grows up to six and a half feet tall where moisture is good – mine towers above a fence creating a lovely, wide screen of bright yellow flowers with downward facing ray petals and prominent green centre cones that transition to brownish black in September. No staking required – strongly upright – although mine needed support during its first year in the garden as well as copious amounts of water. Far less demanding in subsequent years. Large, showy green foliage that is deeply lobed. No pest or disease issues in good growing conditions.


Tall coneflower in background

Solidago spp. (Asteraceae): Native to North America. Drought-tolerant. Pollinators are well familiar with goldenrod but less so is the average gardener. But with the spotlight on pollinator-friendly plants and plants that extend the season, gardeners are poised to fall in love with this underused plant. Numerous cultivars are coming to the marketplace that do not self-seed as aggressively as the species although reseeding can be controlled by pruning off the flowerheads after they finish blooming. Solidago rigida ssp. humilis ‘Golden Rockets’ is a recent introduction that features very stiff flowering stems above a basal mound of broad, green foliage. Bright yellow flowers bloom in late summer. Solidago attracts butterflies such as Harris’s checkerspot. Solidago ‘Fireworks’ is stunning with electric yellow inflorescences.

Sporobolus heterolepis (Poaceae): Native to North America. Common name is prairie dropseed. A larval host plant for skipper butterflies. The seeds are a food source for songbirds. A low-growing ornamental grass with splendid form and texture and late fall colour.

Symphyotrichum novae-angliae (Asteraceae): Native to eastern North America. Common name: New England aster. It is attractive to butterflies. The nectar is easy to access for pollinators.

Thalictrum delavayi (Ranunculaceae): Native to China. Common name: meadow rue. The tiny lavender flowers of Thalictrum ‘Splendide’ start blooming in late August and create a mauve cloud of lavender on extraordinarily tall stems (7 to 8 ft). My plant has to be staked. The bloom display lasts until frost. Sun to part-shade. Attractive to bees.

If bees want something shorter, Thalictrum rochebruneanum ‘Lavender Mist’ has a mature height of 3 to 4 ft. Dainty lilac flowers with showy yellow stamen in mid-to late summer. There is a wonderful display of Thalictrum at Canada’s Diversity Gardens, Assiniboine Park.

Verbena bonariensis (Verbenaceae): Native to South America. Common name: tall verbena. Not hardy to our climate but is self-seeding. A veritable magnet for bees from mid-summer to frost.

Vernonia fasciculata (Asteraceaea): Native to southern Manitoba. Commonly known as ironweed or fascicled ironweed. A nectar plant for butterflies and larval host for the painted lady butterfly. Also attracts bees. A late season perennial with purple flowers that stands tall (1 to 2.5 feet) on strong stems. I don’t grow ironweed in my garden, but Master Gardener Kelley Liebzeit planted ironweed some time ago at the Whyte Ridge butterfly garden where she volunteers and shared with me that it came back reliably every year and did not aggressively reseed. This fall she plans to sow seed as well as start seed indoors. Ironweed is available through Prairie Flora and Prairie Originals.

In Manitoba, fascicled ironweed has been listed as endangered under the Endangered Species and Ecosystems Act.

Conservation starts at home and gardeners have an opportunity to make a substantive difference by growing a diversity of plants.

All photos by Colleen Zacharias, colleenizacharias@gmail.com


False Sunflower and Thalictrum rochebruneanum

Helenium

Published: September 2021