Native alternatives to butterfly bush

Recently at the Birds & Blooms blogs, Carole Sevilla Brown wrote about the problems butterfly bush is causing in many areas of the United States. Although commonly recommended for butterfly gardeners, the most commonly available butterfly bush in the horticultural trade, Buddleja davidii, is native to east Asia and is an invasive species in many areas of the United States.

So far, Canada's cold climate has apparently prevented B. davidii from becoming naturalized here, except in parts of British Columbia (Tallent-Halsell and Watt, 2009). However, each mature butterfly bush can produce millions of seeds, and these seeds can be spread by cars and trains (Tallent-Halsell and Watt, 2009). So a butterfly bush in Toronto could contribute to the problems our neighbours to the south are facing. In addition, climate change is likely to make Ontario's climate milder and therefore put our wild spaces at greater risk from butterfly bush invasion.

Luckily, there are many alternatives for butterfly gardeners. Growing native species avoids the problems of habitat destruction caused by invasives, and can provide better attraction for butterflies by providing food for caterpillars as well as adult butterflies (Tallamy 2009).

With that in mind, here are a few flowering shrubs native to Ontario, which I found through Lady Bird Johnson Wildflower Center's Plants Database. This is a great resource for wildlife gardeners throughout the United States and Canada; you can search by state/province, habit, lifespan, light needs, moisture needs, bloom season, bloom colour, and height! Each species description at the Wildflower Center's database includes a wealth of information, including which butterflies' and moths' larvae feed on each plant, and links to their descriptions at Butterflies and Moths of North America (BAMONA).

Native Ontario shrubs to attact butterflies

• Amelanchier alnifolia (Saskatoon serviceberry): fragrant white flowers in spring. Berries are red to black in colour, attract birds, also edible for humans. Autumn foliage is yellow, orange, or red.
• Amorpha canescens (leadplant): small shrub with spikes of striking dark purple flowers in early summer; attractive silvery foliage.
• Ceanothus herbaceus (Jersey tea): umbels of white flowers in spring to early summer. Larval host for mottled duskywing (Erynnis martialis).
• Cephalanthus occidentalis (buttonbush): nifty spherical clusters of white flowers in the summer. Nutlets attract birds.
• Lindera benzoin (northern spicebush): pale yellow flowers before leaves emerge (male plants have showier flowers). Yellow autumn foliage; red berries on female plants. Larval host for spicebush swallowtail (Papilio troilus), eastern tiger swallowtail (Papilio glaucus), and promethea silkmoth (Callosamia promethea).
• Spiraea alba (white meadowsweet): spikes of white flowers in the summer, yellow autumn foliage. Larval host for spring azure (Celastrina ladon).
• Spiraea tomentosa (steeplebush): steeple-shaped clusters of pink flowers in summer. Larval host for Columbia silkmoth (Hyalophora columbia).
• Viburnum acerifolium (maple-leaf viburnum): clusters of white flowers in spring and summer followed by red to black berries which attract birds. Pinkish-purple autumn foliage! Larval host for spring azure (Celastrina ladon).

I'm so glad that Carole wrote her original post, as I didn't realize that butterfly bush was such a problem, nor did I know much about these lovely native shrubs that we can grow instead. I've got seeds for buttonbush stratifying right now, and I plan to look into some of these other shrubs as well. Please click the links for each plant to see gorgeous photos; I hope you'll be as excited about these plants as I am and try some in your garden!

Works cited

• Nita Tallent-Halsell and Michael S. Watt (2009). The Invasive Buddleja davidii. The Botanical Review, September.
• Douglas W. Tallamy (2009). Bringing nature home: How native plants sustain wildlife in our gardens (updated and expanded edition) Portland, OR: Timber Press.

Penstemon hirsutus in bloom!

The hairy penstemon (aka "hairy beardtongue", "eastern penstemon", penstémon hirsute) that I purchased a few weeks ago at the North American Native Plant Society plant sale a few weeks ago is already blooming, despite the stress of moving to a new home and this crazy heat wave we've been having. I knew very little about this plant when I got it, except that it was a purple penstemon. I'm quite happy with it.

In this close-up, you can see that the dainty flowers are actually bicoloured, mauve and white. Walter Muma's Ontario Wildflowers site has much better close-ups; in the fourth photo down you can see why one of the common names is "beardtongue".

Hairy penstemon is a larval host plant for the beautiful Baltimore checkerspot butterfly. According to Michigan State University, hairy penstemon attracts beneficial insects, including parasitic wasps and pirate bugs, which prey on nuisance insects. This lovely plant also provides nectar for hummingbirds, according to the Ontario Hummingbird Project.

Asclepias syriaca

Note: this plant is legally considered a noxious weed in Ontario (but grow it anyway).

Asclepias syriaca, known in English as "common milkweed", "butterfly flower", "silkweed", "silky swallow-wort", or "Virginia silkweed", and in French as asclépiade commune, bébé lala de lait, herbe à ouate, or herbe aux perruches, is a perennial native to eastern and central North America. The "milk" in milkweed is its thick white sap, which is poisonous to many animals. Some insects, most famously the monarch butterfly larva, are able to feed on milkweed. Monarchs store the toxins in their bodies as a deterrent to predators.

The field behind my mom's apartment buidling in Almonte (eastern Ontario) is dominated by various non-native flowers, but the milkweed is one native that is holding its own. When I checked the undersides of the leaves on this vigorous clump, I found many eggs, probably monarchs. You can see how a big group of milkweed like this would be a butterfly magnet!

The clusters of muted pink flowers are attractive to many different pollinators.

Now, technically, this milkweed is considered a noxious weed under the Ontario Weed Control Act. (Asclepias viridiflora, Asclepias incarnata, and Asclepias verticillata are also listed as noxious.) Milkweed is toxic to livestock and can also invade fields of crops, reducing their yield, so if you are farming or live near a farm you'll want to control or remove milkweed. But I don't think that applies to most of us here in Toronto.

The asclepias are a vital genus of plants for monarch butterflies; they are the only plants that their larvae can eat. If milkweeds are eliminated everywhere, then so to will be the monarch butterflies. So I think that those of us who aren't near farms should make an effort to include some of the asclepias in our gardens if growing conditions are suitable.

The Ontario Weeds Act FAQ states:

As long as the population of milkweed planted doesn't negatively affect agricultural or horticultual land by spreading seed and new vegetative plant material (i.e. root stock) into fields, nurseries or greenhouses then it is acceptable to plant milkweed in your garden. It is recommended that you consult with your local weed inspector and/or neighbours so that all parties involved are comfortable that the impact to agriculture or horticulture is negligible.

Asclepias tuberosa: flowers

Asclepias tuberosa, known in English as butterfly weed, butterfly milkweed, butterfly flower, pleurisy root or glory flower (the last is an apparent marketing ploy to win over gardeners who won't grow "weeds"), and in French as asclépiade tubéreuse, is a perennial native to eastern North America. Although related to the common milkweed, Asclepias syriaca, butterfly weed lacks milky sap. The leaves are narrower than milkweed, dark and glossy, and the flowers are a vivid orange (there are yellow and red cultivars available). Like milkweed, butterfly weed (indeed, all of the Asclepias species) is a larval host for the monarch butterfly.

I purchased the plant in the photo from Real Canadian Superstore in 2007. It didn't bloom at all the first year I had it, or show much growth at all. I was pleasantly surprised in 2008 when it emerged at least three times as big as the year before and with lovely blooms.