Smooth Aster 

It’s fall, the time for Goldenrods and Asters. For this month’s Plant of the Month, I will be covering Smooth Aster – a beautiful purply-blue, prolifically blossoming fall staple in the garden. One of the earlier asters to bloom in my garden, it signals the coming of autumn with its cooler temperatures and fall colours. As usual, the Plant Description and In the Garden sections are courtesy of Shaun Booth from In Our Nature. 

Symphyotrichum laeve (Smooth Aster) and Solidago nemoralis (Gray Goldenrod) – the colours of autumn

Common Name: Smooth Aster 

Scientific Name: Symphyotrichum laeve 

Family: Asteraceae (Aster Family) 

Alternate Common Names: Glaucous Aster, Purple Aster, Smooth Blue American Aster, Smooth Blue Aster, Smooth-leaved Aster 

Plant Description: Smooth Aster features one to a few erect, hairless stems that are usually green but can be a reddish colour. Leaves clasp the stems in an alternate pattern and measure about 10 cm long and 4 cm wide. They are smooth (almost waxy), shiny, toothless, and greenish blue on top and light green underneath. The basal leaves are toothed with winged petioles and are oblanceolate. Open, branching flower clusters are found at the top of the plant. Flowers can also arise from upper leaf axils (where the leaves meet the stem). Individual flowers measure up to 2.5 cm across and feature 15 to 30 oblong ray florets (petals) surrounding yellow centres that turn purplish red with age. Petal colour can vary from light blue to light purple. Four to six layers of bracts surround the base of each flower. They are smooth, appressed (flattened), and light green to bluish green and have diamond-shaped ends with a dark tip. Flowers give way to dry, brown, narrowly cone-shaped seeds, each with a tuft of light brown hairs that allow them to be carried by the wind. 

In the Garden: Smooth Aster is valued by gardeners for its copious blue blooms and non-aggressive growth habit. The flowers are frost hardy and bloom late into fall while the tough stems will persist through the winter months. Smooth Aster is easy to grow but doesn’t like being shaded by taller plants. A favourite food of rabbits, possibly due to the smooth leaves. 

Skill Level: Beginner 

Lifespan: Perennial 

Exposure: Full sun 

Soil Type: Any well-drained soil 

Moisture: Dry 

Height: 20–70 cm (occasionally to 120 cm) 

Spread: 30–60 cm 

Bloom Period: Sep, Oct (to frost) 

Colour: Blue 

Fragrant (Y/N):

Showy Fruit (Y/N):

Cut Flower (Y/N):

Pests: No serious insect or disease problems, though powdery mildew can affect the plant in some years 

Natural Habitat: Fields, open woods, and roadsides 

Wildlife Value: The nectar and pollen of the flower heads attract many species of native bees, butterflies, and other insects and Ruffed Grouse (Bonasa umbellus) and Wild Turkey (Meleagris gallopavo) feed on both the leaves and seeds of asters; the seeds are also eaten by mice and American Tree Sparrows (Spizelloides arborea

Butterfly Larva Host Plant For: Silvery Checkerspot (Chlosyne nycteis), Tawny Crescent (Phyciodes batesii), Northern Crescent (Phyciodes cocyta), Pearl Crescent (Phyciodes tharos), Painted Lady (Vanessa cardui

Moth Larva Host Plant For: At least 40 species of moths, including members of the tiger moths, ribbed cocoon-maker moths, case-bearer moths, twirler moths, geometer moths, leaf-blotch miner moths, slug caterpillar moths, owlet moths, clearwing moths, flower moths, trumpet leafminer moths, and tortrix moths. 

USDA Hardiness Zones: 3–9 

Propagation: Direct sow the seeds in late fall or early spring. No pretreatment is necessary even when starting indoors, but seeds need light to germinate. Germination is said to be slow. Transplanted seedlings will likely bloom in their first year. You can also multiply plants from root cuttings. 

Additional Info: Symphyotrichum laeve will tolerate short durations of seasonal flooding. It also self-sows strongly in open areas that are burned and mowed and is walnut (juglone) tolerant. 

Native Range: 

Fall Garden Prep for the Native Plant Garden 

The leaves are starting to turn colour, the air is getting cooler, and there are lots of gardening articles being written about what to do with your Canna Lilies and rose bushes and dahlias for the winter. But what about those of us who grow native plants? Do we have to do anything to prepare our plants and flower beds for winter? After all, Mother Nature has been looking after herself for millennia. 

How much fall prep you do will depend primarily on WHY you grow native plants.  

Leave the Plant Stalks 

When I started growing natives, I came from a background of conventional gardening, and the easiest way to put my native plant gardens to bed for the winter was to simply set my mulching mower as high as it would go and mow everything down. The result was a tidy looking flower bed that was ready to emerge in the spring.  

In the spring, after an extensive fall clean up, the flowerbeds looked tidy, but there was no shelter for overwintering insects.

Unfortunately, I also removed important habitat for bees and other insects. 

As my understanding grew of the importance of leaving stems for leaf cutter and wool carder bees and for small carpenter bees and others, I had to change my mind set. I started to leave a few of the pithy stems of Monarda (Bee Balm and Wild Bergamot) but I still “cleaned up” the rest of the flower beds by cutting down the asters, Joe Pye weed, coneflowers, etc. and hauling the debris to the municipal yard for composting.  

Leaving those stems was really hard to do – at first. It offended my sensibilities as to what a neat and tidy garden should look like for the winter. But whether it was my imagination or reality, I thought I detected more bees the next year, and more species of bees as well. So when fall rolled around again I compromised – I cut down most of the plants to about 18”, and rather than hauling the debris away, I cut it into 1-2’ lengths and left it on the ground.

Because my gardens are very densely planted, and some with very tall plants, I would have had a foot of cuttings if I dropped them all in the garden, so I kept it to a minimum by leaving one thin layer in the flowerbed, and placing the remaining stems in an out of the way corner of the yard. 

Surprisingly, it was my mindset that had the greatest change as a result of this new strategy. I no longer saw a “mess” in the flowerbed in the fall. Instead, I saw potential habitat. I saw that I was giving Mother Nature a helping hand. It’s one thing to provide native plants for bees, butterflies and caterpillars to feed on during the summer, but if you don’t provide them with a place to overwinter, then you are really only helping those species that migrate. 

Leaving the flower stalks has, in addition to the wildlife benefit, the added beauty of great structure in the winter garden. 

But is leaving the stems the only thing we can do?  

Leave the Leaves 

Leaving the leaves on our lawns is just about as difficult to do as leaving plant stems in the gardens for the winter for most of us. But it is just as important. I do rake my lawn in the fall, but I have much less area of lawn than I do of flowerbeds, so the leaves get raked onto the beds. They provide mulch to keep annual weeds down in the spring, and fertilizer as the leaves decay. And depending on the bed, I may put just a thin layer (on the beds of prairie species, for example) or a layer at least 6” thick under the sugar maples where Trilliums, Jack in the Pulpit, and other spring ephemerals need the organic matter and moisture retaining quality of the decaying leaves.  

Most of our spring forest wildflowers require deep, humus-rich soils to flourish. Decaying leaves provide this.

I actually have so many trees in my yard now that I now create piles of the excess leaves in the fall to be spread over the shade garden in mid-May when most of the leaves there have been consumed by insects, worms and microbes.  

But why is it important to leave the leaves, other than for mulch and natural fertilizer? 

For starters, many of our butterflies and some of our more spectacular moths overwinter in the leafy debris. 

According to the Royal Ontario Museum’s book Butterflies of Ontario, of the 127 species of butterflies in this province, 110 overwinter here.  

  • 6 overwinter as adults 
  • 12 overwinter as eggs 
  • 30 overwinter as a chrysalis 
  • 60 overwinter as a caterpillar, and  
  • 2 overwinter as either a caterpillar or a chrysalis. 

Many of these hide either in the leaf litter or in the ground (where the leaf litter helps to keep them warm). 

Many of our moths do the same. The ones we tend to get excited about – the large, showy ones – are no different. For instance, the beautiful green Luna Moth overwinters by using its silk to bind dead leaves around its cocoon. The Virgin Tiger Moth overwinters as a caterpillar, hiding in the leaf litter. And as for everyone’s favourite – the Hummingbird Clearwing Moth – the fully-grown caterpillars burrow in the leaf litter to pupate, emerging soon after and overwintering as an adult, or waiting in the cocoon until the following spring to emerge.  

So the less we can disturb the leaf litter, the better, as far as I am concerned.  

Do it for the Bees, Too 

We also have a number of ground nesting bees that greatly benefit from a quilt of leaves to help maintain a comfortable temperature all winter long. The leaves have the added benefit of slowing down the heating of the soil in a January thaw that might cause the bees to emerge too early before any food sources are available. 

The American Sand Wasp (Bembix americana) is just one of many ground nesting bees and wasps. These wasps are solitary predators that primarily target flies – including the annoying horse and deer flies – for their developing larvae. When the larvae mature, the tunnel is sealed for the winter. They pupate in spring and come out from their tunnels in summer.

As you start thinking about preparing your garden for its long winter rest, think of the insects that need the stems and leaves to survive till spring. Leave some stems, and leave the leaves. 

Campanulastrum Americanum

Common Name: Tall Bellflower 

I’ve long admired these growing in an old-growth forest bottomland near me, but only recently found them at a native plant nursery. I think they are far nicer than the invasive Creeping Bellflower, and wish they were more commonly available in garden centers. (As usual, the Plant Description and In The Garden sections are written by Shaun Booth, formerly from In Our Nature)

Scientific Name: Campanulastrum americanum  

Family: Campanulaceae (Bellflower Family) 

Alternate Common Names: American Bellflower 

Plant description: Tall Bellflower features erect, hairy, mostly unbranching stems with slight grooves along them. The leaves are found in an alternate pattern and measure about 7.6cm – 15cm long and 1.2cm – 5cm across, becoming smaller as they ascend the stem. They are lance to egg shaped, taper to a sharp tip, hairy along major veins on the underside with a rough upper surface and have serrated margins. The leaf base narrows to hairy leaf stalks. Stems terminate with a flowers spike measuring 15cm to 60cm long with shorter flower spikes emerging from leaf axils (where the leaf meets the stem). Individual flowers are 2.5cm across with 5 blue petals and a creamy white center ring. The petals have wavy edges and pointed tips. Each flower has a style (reproductive organ) protruding from the center of the flower. Flowers give way to three sectioned seed capsules up to 1.2cm long that release numerous tiny brown seeds when mature.  

Not to be confused with the common exotic garden weed, Creeping Bellflower (Campanula rapunculoide) which has more bell-shaped flowers compared to the saucer shaped flowers of Tall Bellflower. Creeping bellflower is also much shorter and more aggressive. 

Not native (and considered invasive in most jurisdictions in northeastern North America and beyond) is Campanula rapunculoides – Creeping Bellflower.

In the Garden: Tall Bellflower adds a strong vertical presence to gardens with delightful spires of violet-blue, star-shaped flowers. If its seeds are started in fall, then it acts as an annual. If its seeds are started in spring then it acts as a biennial. Due to its short-lived nature, it will persist in your garden via self-seeding. 

Skill level:  beginner 

Lifespan: annual/biennial 

Exposure: sun to light shade 

Soil Type: rich loam, clay, sand, circumneutral (pH 6.8-7.2)  

Moisture: moist to medium (plants need regular and even moisture) 

Height: 150-200 cm 

Spread: 30-60 cm 

Bloom Period: Jun, Jul, Aug 

Colour: blue 

Fragrant (Y/N):

Showy Fruit (Y/N):

Cut Flower (Y/N):

Pests: no serious insect or disease problems though slugs and snails are occasional visitors, and watch for aphids 

Natural Habitat: marshy ground, stream banks, openings in deciduous forests, and in disturbed areas such as trails, edges of fields and along railroads 

Wildlife Value: A number of bees, including bumblebees and leaf cutting bees, butterflies and skippers, seek nectar and or pollen, and deer occasionally eat the flowers and foliage 

Butterfly & Moth Larva Host Plant For: none 

USDA Hardiness Zone: 4-7 

Propagation: [NT, L] No treatment needed as seeds germinate easily, but they require light to break dormancy, so do not cover the seeds.  

Additional Info: Deadhead spent flowers to encourage additional bloom. Plants are annual or biennial but will easily remain in a garden by self-seeding. Tall bellflower is listed as Endangered in New York State. 

Native Range: 

Native range (shaded) of Campanulastrum americanum – American Bellflower.

Got Shade? Part 2 – Summer in the Shade 

This spring, I wrote an article about spring ephemerals – those woodland species that flower early in the spring and then, for the most part, disappear till the following year. Summer has arrived and we have a number of shade tolerant plants for your woodland gardens that bloom through the summer and into the fall. In today’s article, I’ll talk about some of these and share some images from my shadier gardens. 

Plants that grow under the tree canopy of a forest have to be tough. Not only do they need to compete with tree roots for moisture, they need to be able to collect light that filters through often dense canopies of leaves. Many of these plants collect as much energy from the sun as possible before the trees leaf out, then “coast” on that stored energy for the rest of the summer. But a few plants buck the trend and manage to grow, produce flowers and set seed under shady conditions that few others could tolerate.   

One thing I have observed that almost all these plants have in common is large leaves. They require maximum leaf area to absorb the few photons of light that filter through the trees, with their leaves designed to work at maximum efficiency. (Compare, for instance, the leaf of shade tolerant Asclepias exaltata – Poke Milkweed – to those of the sunny, open prairie species Asclepias verticillata – Whorled Milkweed or of the shade tolerant Lobelia inflata – Indian Tobacco – with the sun-loving Lobelia spicata – Pale Spiked Lobelia). 

Another thing I have noticed these plants tend to have in common is that their flowers are mostly white, green, pale blue or pale yellow (at least until the fall, when a few brighter colours – mostly yellows – appear). Whether this has to do with the plants requiring more energy to produce colourful flowers (speculation on my part) or because in shady areas these colours show up more for the pollinators to find, I have no idea. Two exceptions are the brilliant reds of Monarda didyma (Beebalm) – not normally associated with shade gardens, but it thrives in moist dappled shade in my garden – and Lobelia cardinalis (Cardinal Flower). 

It is the end of July as I write this, and a few late-spring/early-summer shade tolerant plants have now finished blooming and are setting seed. These include Thalictrum pubescens (Tall Meadowrue), T. dasycarpum (Purple Meadowrue), T. revolutum (Waxy Meadowrue) and Asclepias exaltata (Poke Milkweed). 

Monarda didyma (Beebalm) and Lobelia cardinalis (Cardinal Flower) are both in full flower right now in full light shade where they brighten dark corners with a brilliant flash of colour, and attract hummingbirds and butterflies. And new to my shade garden this year, but doing nicely, is the porcelain blue Campanulastrum americanum (American Bellflower). Lobelia inflata (Indian Tobacco, aka Puke Weed) is also flowering now in full (but relatively light), moist shade with delicate, pale bluish flowers. 

Just starting to bloom in my shade gardens are Eurybia macrophylla (Large-leaf Aster), Eurybia schreberi (Schreber’s Aster), Aralia racemosa (American Spikenard), Ageratina altissima (White Snakeroot), Actaea racemosa (Black Cohosh), Scrophularia marilandica (Late Figwort) and Circaea lutetiana (Enchanter’s Nightshade). These are joined by a large patch of Impatiens pallida (Yellow Jewelweed). Even some Veronicastrum virginicum (Culver’s Root), another plant like Beebalm that isn’t normally thought of as a shade tolerant plant, is doing great under the dappled shade of Gymnocladus dioicus (Kentucky Coffeetree). 

We also have some lovely plants suitable for part shade. These would normally be found at the edges of forests, and can tolerate quite a bit of shade. However, many of them tend to flower more prolifically with the benefit of more sunlight. Most books suggest that Solidago juncea (Early Goldenrod) requires full sun, but it is doing well under a large sugar maple in my yard where it gets only a half hour or so of direct, late afternoon sun. As its common name suggests, it is one of the earliest goldenrods to flower and starts flowering in my southwestern Ontario garden around the third week of July.  

A number of other shade plants – mostly asters and goldenrods, but also some interesting woodland species – will start to bloom in the next few weeks but I’ll leave those for a later article. We also have lots of shade-loving ferns, grasses and sedges, and a few great shrubs for shade, but those, too, will have to wait. 

Note that none of the plants listed above will thrive in deep shade such as that often found under Norway Maple, evergreens (like spruce or cedar) or close to the north side of a building, but they will all do very well in dappled shade (from less dense canopies such as under Kentucky Coffeetree) or if planted near the edge of the shade where they can get sun for at least part of the day.  If you do have deep shade, you may want to consider some of our spring ephemerals mixed with ferns, for now. 

Happy native plant gardening. 

Canada Lily 

Some of the most popular posts on my Facebook page are the images of my Canada Lily (Lilium canadense). Technically not native to the part of Ontario that I live in (it could be classified as a “near native” here), it nevertheless thrives in my garden. Each year this plant sends up more shoots and has more blossoms.  

I planted it as a small potted plant five years ago. A year later it was about 4’ tall and had two blossoms. The next year it shot up to just over 7’4” and had 24 blooms. Last year a second stalk appeared and the taller one reached an amazing 7’9” and there were 53 blooms between the two plants. This year, it just got bigger and more spectacular. A total of 8 stems produced 102 flowers and the tallest of these plants reached an incredible 7’11.5”. 

In this month’s Plant of the Month I am writing about this amazing species.  As usual, the Plant Description and In the Garden sections are courtesy of Shaun Booth from In Our Nature. 

Common Name: Canada Lily 

Scientific Name: Lilium canadense 

Family: Liliaceae (Lily Family) 

Alternate Common Names: Meadow Lily, Wild Yellow Lily, Yellow Wood Lily 

Plant Description: Canada Lily features smooth, light green stems that are unbranched, except at the top where the flowers are found. Leaves are distributed along the stem in whorls of three to eight with some smaller alternate leaves occurring along the upper portion of the stem. Each leaf is up to 15 cm long, 2.5 cm wide, smooth, toothless, and narrowly ovate. Stems terminate with up to 20 nodding, trumpet-shaped flowers borne on long stalks and can range in colour from reddish orange to yellow. These flowers are up to 10 cm across and feature six tepals that flare backwards (but not past the base of the flower), six stamens, and dark dots on the inside of the tepals. Flowers become oblong, 5 cm long seed capsules that are divided into three cells containing flat seeds. 

In the Garden: Canada Lily adorns the summer garden with trumpet-like flowers that hang gracefully from the plant. Besides its blooms, it is valued for its clumping habit and interesting whorled foliage. 

Skill Level: Beginner to intermediate 

Lifespan: Perennial 

Exposure: Full sun to part shade (prefers dappled shade) 

Soil Type: Rich loamy or slightly sandy soil 

Moisture: Moist to medium 

Height: 90–240 cm 

Spread: 15–20 cm 

Bloom Period: Jun, Jul, Aug 

Colour: Red, orange, or yellow 

Flowers may be yellow, orange, red, or a combination.

Fragrant (Y/N):

Showy Fruit (Y/N):

Cut Flower (Y/N):

Pests: The caterpillars of several moth species feed on the leaves, stems, and corms of Canada Lily, and the introduced Lily Leaf Beetle or Red Lily Beetle (Lilioceris lilii) feeds on its leaves 

Natural Habitat: Wet meadows, moist rich woods, streamsides, and wetlands, and along wet roadsides and railroads 

Wildlife Value: The nectar attracts large butterflies, particularly the Great Spangled Fritillary (Speyeria cybele) and various swallowtail butterflies. Some bees collect pollen from the flowers, but they are ineffective at cross-pollination because of their small size. A number of mammalian herbivores browse on the foliage, and voles and chipmunks are known to eat the corms. Rabbits ate off several new lilies I planted last year, and squirrels dug out the corms of others before I had a chance to cover them with chicken wire – but once established the plants seem pretty robust. 

Butterfly Larva Host Plant For: None 

Moth Larva Host Plant For: Carrion Flower Moth (Acrolepiopsis incertella), Burdock Borer Moth (Papaipema cataphracta), Golden Borer Moth (Papaipema cerina), Common Borer Moth (Papaipema nebris), Sparganothis Leafroller Moth (Sparganothis sulfureana

USDA Hardiness Zones: 4–8 

Propagation: [WC; D] Canada Lily seeds must undergo a period of one to two months of warmth, at which time they will swell and become a small bulb. These then need another 60 to 90 days of cold before they begin to sprout. Seedlings typically go dormant by midsummer. Plants grown from seed will take five to six years before they flower. Propagation is easiest from division of the scaly bulb, which can be dug as soon as the plant goes dormant in late summer. 

Additional Info: Canada Lily is primarily pollinated by the Ruby-throated Hummingbird (Archilochus colubris) and large butteflies such as the swallowtails. Canada lily is listed as Threatened in Indiana. 

Native Range (shaded area on map):