Butterfly Gardens

Helping You Help Nature

Blue Vervain

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Image Credit: Cody Hough, Wikimedia Commons

Blue Vervain (Verbena hastata) is a stunning wildflower that can reach heights of up to 1.5 m. Native to North American and cold hardy to Zone 3, it grows in every American state and in every Canadian province except Alberta and Newfoundland. It’s a terrific addition to a butterfly garden, particularly in the United States. It’s a food source for the larvae of the common buckeye butterfly, which primarily flies in the U. S. A.

Recognizing Blue Vervain

Also known as swamp vervain and swamp verbena, it’s no surprise that blue vervain grows naturally in the moist soils found along riverbanks, marshes, ditches, and shores. In a home garden, it does particularly well in low-lying areas and around the edges of ponds.

According to the United States Department of Agriculture, blue vervain has square stems that might be green or red and are often hairy. Pairs of leaves grow along the stems. Leaves are long and narrow (about 15 cm by 2.5cm). They are also toothed.

The upper stems of the plant branch out into panicles, which are clusters of flowers on spikes. Each spike is about 13 cm long.  While a single spike will produce dozens of blossoms, only a few flowers open at one time. Over the course of the blooming period (June through August), flowers will begin opening from the bottom of the spikes and progress to the top. The tiny blue-violet flowers are only about 0.5 cm across. The Illinois Wildflowers website describes the flowers as having, “a blue-violet corolla with 5 spreading lobes, a short-tubular calyx with 5 narrow teeth, 4 inserted stamens, and a pistil. The calyx is grayish green to dark red and about one-half as long as the corolla.”

About six weeks after blooming, each bloom changes to four “nutlets.” The nutlets are reddish brown and tiny–just 2 mm long. Nutlets can be collected for plant propagation. However, Kansas State University cautions about plant identification. There are several other species of verbena that look quite similar to blue vervain, including hoary vervain (V. stricta), narrow-leaved vervain (V. simplex), pink vervain (V. pumila), nettle-leaved vervain (V. urticifolia), and fanleaf vervain (V. plicata). While each could be a lovely addition to your garden, only blue vervain will attract the common buckeye butterfly.

Growing Blue Vervain

Blue vervain isn’t  the easiest wildflower to introduce to your garden. The United States Department of Agriculture explains that blue vervain is best propagated by seed, which needs to be cold stratified and started indoors. But once established, blue vervain will self-seed for an impressive garden display.

Start by collecting nutlets from wild plants in late summer or early fall. Spread the nutlets out over a protected indoor surface and let them dry for several days. Once dry, the nutlets need to be crushed lightly in order to remove their seeds.

Seeds must be cold stratified in order to germinate. Mix the seeds with wet sand or peat moss and seal everything into an airtight container or bag. Store in the refrigerator, at 3-4 degrees Celsius, for three months. When the cold stratification period is over, create a mix of one part sand to two parts soil. Put the soil mix into seed trays or pots and lightly press the seed mix into the soil. Keep the pots under grow lights, at about 15-26 degrees Celsius. The seeds should germinate in about 5-15 days.

When ready to plant out, choose a spot that has full sun to part shade and rich, moist soil. Once established, blue vervain requires little care other than pinching the tops back a few times during the growing season. This encourages bushier, fuller growth.

Blue vervain blooms in mid- to late summer. Bloom time lasts for about 4-6 weeks as the blossoms gradually unfurl up the plant’s spikes.

Blue Vervain and Butterflies

Blue vervain is a host plant for the common buckeye butterfly, which is quite striking in appearance. The Butterflies and Moths of North America website describes these butterflies as being primarily brown with distinctive markings. The upperside of the both the forewings and the hindwings have a pair of eyespots, one small and one larger pair. It’s speculated that the eyespots are a way to scare away predators.

The forewings also each have two orange cell bars and a white band. The underside of the wings is paler in colour, particularly in the summer, but the markings are repeated.

Common buckeye butterflies are most often found in the southeastern United States and in California, with some sightings in the southern western and midwestern states. The Butterflies and Moths of North America website says that these insects migrate north in the summer to colonize the northern states and southern Canada. However, the Canadian Biodiversity Information Facility website says that the insects are “normally only a rare stray in Canada[.] But in good migrant years temporary colonies can become established, and the Common Buckeye becomes locally common for one season.”

Part of the fun of establishing a butterfly garden is to see which species visit. Why not plant some blue vervain to see if the gorgeous common buckeye butterflies fly on through?

Asclepias Tuberosa

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Asclepias Tuberosa
Image credit: SB_Johnny on Wikimedia Commons

Milkweed is known for attracting monarch butterflies (Danaus plexippus).There are over 200 species of milkweed but Asclepias tuberosa is commonly known as butterflyweed and butterfly milkweed, and rightfully so. The plant is an important host plant for monarch, grey hairstreak, and queen butterflies. It is also an important nectar source for several other butterfly species. While it is native to North America, cultivars have been developed for home gardens. Asclepias tuberosa is a terrific choice for any butterfly garden.

Recognizing Asclepias tuberosa

Native to North America

According to the U.S. Forest Service, butterfly milkweed grows throughout Ontario and Quebec in Canada. In the U. S. A., the plant grows naturally in all but the northwestern states. It is particularly common in the Midwest and Great Plains regions. In the wild, it grows in prairies, open woods, canyons, and hillsides.

Recognizing Asclepia tuberosa

Butterfly milkweed is a beautiful plant that is often grown in home gardens. Compared to other milkweeds that can grow quite tall, Asclepia tuberosa is fairly compact, growing to about 0.5 to 1 m in height.

The plant has a bushy appearance, with numerous stalks forming a clump. Each stalk has narrow oblong leaves and is often topped by several stems. Each stem may host a flower umbel. (An umbel is a cluster of small flowers atop small stems that are similar in shape to the ribs of an umbrella.) The large umbels on butterfly milkweed are often flat or very slightly domed. These provide a handy “landing pad” for butterflies to rest on while extracting nectar.

Butterfly milkweed blossoms are most often bright orange. In fact, one other common name for the plant is “orange milkweed.” However, the Lady Bird Johnson Wildflower Centre states that the flowers might also be red or yellow–and that yellow blossoms predominate west of the 100th meridian. Blossoms are usually 1 cm across, which is relatively large. (The blossoms on species like Asclepias syriaca and Asclepias incarnata are closer to 0.5 cm across.) There are usually about 25 blossoms in each umbel.

Asclepia tuberosa blooms from June through August.

Asclepia tuberosa in the Garden

Butterfly milkweed is easy to grow and care for. Cold hardy in Zones 3-9, it should be planted in full sun. While it prefers well-drained sandy soil, it will grow in any kind of soil, including gravel and clay. It’s drought-tolerant.

The website for the Master Gardener Program at the University of Wisconsin-Madison explains that Asclepia tuberosa has a long taproot and doesn’t transplant well. It’s best started from seeds or cuttings. It’s easiest to sow seeds directly into the soil in the fall, replicating the way the plant self-seeds in nature. If started indoors, seeds need to go through cold stratification for about a month. Cuttings should be started in the fall as well. Take 5 cm sections from the taproot of an established plant and plant the cuttings vertically.

It will take 2-3 years for butterfly milkweed to bloom. But once established, the plant will become thicker each year, and will last for many years.

The one issue that butterfly milkweed may have is aphids–in particular, oleander aphids. The tiny insects rarely harm their host plant and they are tasty food for ladybugs. But if an infestation is bad, aphids can be removed with soapy water or with a high-pressure spray from a hose.

Asclepia tuberosa and Butterflies

According to the Lady Bird Johnson Wildflower Center, Asclepia tuberosa is a host plant for three different species of butterfly larvae:

  • Monarchs (Danaus plexippus)
    • The monarch is one of the best-known species due to its beautiful orange and black coloration and its annual migration. They are found from coast to coast in North America. The Canadian Biodiversity Information Facility reports that monarchs have been spotted at times “well beyond the northern limits of its foodplants.”
  • Grey hairstreaks (Strymon melinus)
    • According to the Butterflies and Moths of North America website, grey hairstreaks are found throughout the United States, with the largest concentrations on the western coast and in the southeastern states. They are rarely found in Canada, except in the southernmost areas near the international border with the United States. Grey hairstreaks are bluish-grey with a tail and large red spots near the tail.
  • Queens (Danaus gilippus)
    • The Butterflies and Moths of North America website describes queen butterflies as chestnut brown, with a black border around their wings and white spots. The underside of their wings has black veining as well. Queens are found from coast to coast in the southern United States. They have been known to stray as far north as South Dakota and New Hampshire.

In addition to being a food source for some butterfly larvae, Asclepia tuberosa also attracts many other butterflies with its rich nectar:

  • Eastern tiger swallowtails (Papilio glaucus)
  • Fritillaries (subfamily Argynninae)
  • Other hairstreaks (subfamily Theclinae)
  • Painted ladies (Vanessa cardui)
  • Pipevine swallowtails(Battus philenor)

Butterfly milkweed has gorgeous, bright flowers; it’s easy to care for; and it attracts a wide range of pollinators, including several species of butterflies. Whether you’re planning a butterfly garden or just looking for a plant for your flower bed, butterfly milkweed is a terrific choice.

Butterfly Bush

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A branch of a butterfly bush
Image credit: MediaWiki Commons, User IKAl

Butterfly bush (Buddleia davidii) is a magnet for tiger swallowtails, monarchs, and other butterflies and moths. It’s a gorgeous deciduous shrub that usually grows about 2-3m tall. Semi-hardy to Zone 5 and hardy to Zone 9, it may die back to its base in harsh winters. However, if that happens, it usually sends out new growth in the spring. Its blossoms are similar to those produced by lilacs: long spike-shaped trusses of tiny flowers. Masses of the colourful, highly-fragrant, and pollen-rich flowers bloom from summer into fall.

Invasive Species

Butterfly bush is native to China. Known for its stunning, nectar-rich flowers and its ability to thrive in poor growing conditions, it was introduced as an ornamental plant around the world.

The very qualities that make butterfly bush a favourite also cause concern. It’s considered an invasive species in some areas and a noxious weed in others. In Washington State, USA, it’s illegal to buy or sell butterfly bushes (unless they are accepted sterile cultivars).

As the Invasive Species Council of BC points out, each of those gorgeous flower clusters on a butterfly bush can produce over 40,000 seeds. An entire bush can produce up to three million seeds in a single year. Seeds travel on the wind and in water and may remain dormant for years.

Once sprouted, a butterfly bush grows vigorously. It’s drought-tolerant and thrives in poor soil conditions–even growing in sidewalk cracks. It has spread quickly into established ecosystems and protected areas. It can crowd out native plants and alter soil nutrients. Regardless of growing conditions, butterfly bush can produce flowers and seeds in its first year, furthering its invasive cycle.

Sterile cultivars

Despite their issues, butterfly bushes remain extremely popular. A piece at ThoughtCo reveals that “the production and sale of butterfly bush was a $30.5 million industry [in the USA] in 2009.” Neither commercial growers nor home gardeners were keen to give up on the gorgeous plant.

Horticulturalists came to the rescue by developing cultivars that produce less than 2% of the seeds of traditional butterfly bushes. These cultivars are considered non-invasive and have been labelled as sterile. Even some municipalities that outright banned the sale of butterfly bush have amended their laws to allow for sterile cultivars.

Most of the sterile cultivars are hardy to Zones 5-9 and thrive in full sun. More details on select varieties are below:

Buddleia Lo & Behold® “Blue Chip”

This dwarf shrub grows to only about 45-75cm tall. It blooms with fragrant purple-blue flowers from summer until frost.

Buddleia Lo & Behold® “Purple Haze”

This particular cultivar is low (growing to a maximum height of 1m) and wide-spreading. It’s perfect for ground cover. Its fragrant purple flowers bloom from mid-summer to late fall.

Buddleia Lo & Behold® “Ice Chip”

This compact dwarf cultivar has fragrant white flowers that bloom continuously from mid-summer to mid-fall.

Buddleia “Asian Moon”

This tall cultivar can grow to between 1.5-2m in height. It produces stunning purple flowers with orange throats that bloom from summer until frost.

Buddleia “Miss Molly”

With a height of about 1.2-1.5m, this cultivar produces almost-red blossoms that are unique among butterfly bush varieties.

Buddleia “Miss Ruby”

Similar in height and appearance to “Miss Molly,” the Miss Ruby cultivar produces rich pink blossoms.

Not a True Host Plant

There is another issue with butterfly bush, though. While it provides abundant nectar for butterflies, it doesn’t support butterfly larvae or other types of wildlife. No caterpillars in North America will eat the leaves of butterfly bushes. Without caterpillars, there would be no butterflies. Butterfly bush is not truly a host plant since it doesn’t support butterflies through their entire reproduction and life cycle.

Create a Butterfly Host Garden

There’s nothing wrong with planting a butterfly bush just because you think it’s a beautiful plant. But if you’re truly interested in supporting butterfly populations, it’s better to create a host garden.

To give larvae something to munch on, establish companion plantings to your butterfly bush. Native plants that work well for this purpose include butterfly weed, milkweeds, joe-pye weed, and oak trees.

Another alternative is to skip butterfly bush altogether and plant a native alternative shrub instead. The Canadian-based Evergreen website suggests planting these native shrubs:

  1. Red flowering currant (Ribes sanquineum): This deciduous shrub grows up to 4m tall and produces pink draping blossoms that attract butterflies.
  2. Ninebark (Physocarpus capitatus): Produces white blossoms in the spring to attract butterflies. It can grow up to 4m high.
  3. Lilac (Syringa spp.): Lilac bushes are quite visually similar to butterfly bushes and also produce masses of fragrant blossoms. There are many different varieties and cultivars that flower at different times.
  4. Red Elderberry (Sambucus racemosa): This tall deciduous shrub can reach up to 6m in height. It produces white flowers in the spring that attract butterflies.
  5. Oceanspray (Holodiscus discolor): Another tall deciduous shrub that can grow to 4m in height. In the spring, it produces creamy white blossoms as plumes.

Butterfly bush is visually stunning, thrives in poor growing conditions, and produces ample nectar for butterflies. It sounds amazing but it’s not the best choice for a butterfly garden. Since it’s not native to North America, it didn’t evolve in tandem with our other plant and animal species. For that reason, it’s not a good host plant for wildlife, including butterfly larvae. Further, unless you choose a sterile cultivar, its invasive tendencies may cause issues in your region’s ecosystem. For all these reasons, it’s better to choose native plantings for your butterfly garden.

Asters

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A poster of twelve different species of flowers of the family Asteraceae, belonging to the three most representative subfamilies: Asteroideae, Cichorioideae and Carduoideae
Image Credit: Alvesgaspar, Tony Wills (10)
[CC BY-SA 3.0 (https://creativecommons.org/licenses/by-sa/3.0)]

Asters are a beautiful–and easy-to-care-for–addition to any garden. Typically blooming in late summer and fall, the plants produce striking composite flowers. The fragrant and colourful blooms attract butterflies, bees, and birds. With over 600 species to choose from, it’s easy to find a variety that suits your garden’s setting and microclimate.

Flowering Characteristics

A flowering aster is a beautiful plant. It produces small (1-5 cm) daisy-like blooms that are composite flowers. As the Canadian Wildlife Federation explains, “this means that each flower is actually a group of smaller flowers consisting of ray flowers (petals) surrounding disk flowers (the centre). Disk flowers are usually yellow or burgundy, which makes a nice contrast with the blue, purple, violet, or white ray flowers.”

The colourful, fragrant blooms attract birds and insects, including butterflies. Most aster varieties bloom in late summer to early fall. As the Ontario Parks website points out, that timing means that asters are an important source of nectar for monarch butterflies as they ready themselves for their migration to Mexico.

But asters are an important food source for other butterflies too and the larvae of many different butterflies and moths.

Habitat

Asters are native to North America (including Canada) and southern Europe. Most species are perennials, but there are a few that are annuals or biennials. They grow in the wild across Canada, propagating by seeds dispersed on the wind. The plants appear in many different habitats, including wetlands, forested areas, and mountain regions. Different varieties are hardy from Zones 3-8. It is no surprise then that asters are easy to grow.

Some species can thrive in just about any garden. According to the Canadian Wildlife Federation, for example, Lindley’s aster (Aster ciliolatus) grows in full sun to partial shade, in dry to moist soils. Other varieties are more particular. The New York aster (A. novi-belgii), for instance, requires full sun and moist soil to flourish.

Care

As long as you choose a species suited to your garden’s microclimate, asters are one of the easiest perennials to grow. The one issue to watch for is powdery mildew. Be proactive in protecting your plants from this fungal disease by keeping moisture above ground to a minimum. Leave lots of space between plants for air circulation. As well, water at soil level (rather than using an oscillating sprinkler) in the morning so that wet leaves can dry quickly. And, amending the soil with compost is always an excellent way to enhance the health of any garden plants.

Species

The Canadian Wildlife Federation website is an excellent resource for choosing the right asters for your garden’s microclimate. While all asters attract butterflies and moths, cross-check the Carolinian Canada website if you’re planting to attract certain insect species.

Lindley’s Aster or Fringed Blue Aster (Symphyotrichum ciliolatum formerly Aster ciliolatus)

Image Credit: wackybadger [CC BY-SA 2.0 (https://creativecommons.org/licenses/by-sa/2.0)]

This species produces 2.5-3cm flowers. The sparse ray petals are thin and long, and are pale to deep blue or violet in colour. The disc flowers change colour from yellow (when budding and first open) to purple (when pollinated). The changing colour signals pollinators, letting them know which flowers are rich in nectar. The plants range from 30cm to 1m in height.

Lindley’s Aster is native to British Columbia, Saskatchewan, Manitoba, Ontario, Quebec, New Brunswick, and Nova Scotia. It prefers full sun but will grow in partially shaded areas as well. This species is not picky about soils, growing in poor soils and ones that range from dry to moist.

Blue Wood Aster or Heart-leaved Aster (Symphyotrichum cordifolium formerly Aster cordifolius)

Flower heads at different stages
Image Credit: Nadiatalent [CC BY-SA 3.0 (https://creativecommons.org/licenses/by-sa/3.0)]

The small 1.5cm ray flowers on this species may be pale blue, blue-violet, rose, mauve, or occasionally white. Like Lindley’s Aster, the disc flowers of Blue Wood Asters are initially yellow but change to purple. The change in colour lets pollinators know which flowers have nectar available. This variety grows quite tall, ranging from 60cm to 2m in height.

Blue Wood Asters are native to Manitoba, Ontario, Quebec, Newfoundland, New Brunswick, Prince Edward Island, and Nova Scotia. Its natural habitat is in open woods and on the edges of woods. It grows in light shade to full sun and is drought-tolerant.

Heath Aster (Symphyotrichum ericoides, formerly Aster ericoidesoides)

A large bunch of flowering heath aster.
Image Credit: Cody Hough [CC BY-SA 3.0 (https://creativecommons.org/licenses/by-sa/3.0)]

This beautiful aster produces dense clusters of small 1cm white ray flowers that spread along its branches. Its disc flowers change from yellow to brown as a way to direct pollinators to those blooms that have abundant nectar.

Heath Asters grow naturally in the Yukon and Northwest Territories as well as in Alberta, Saskatchewan, Manitoba, Ontario, and Quebec. They prefer open sky and full sun, growing in grasslands, fields, meadows, and ditches. Heath Asters are not picky about soil types or moisture levels.

Heath Asters are one of the host plants for silvery checkerspot and northern pearl crescent butterflies.

New England Aster (Symphyotrichum novae-angliae formerly Aster novae-angliae)

A single New England aster
Image Credit: Hugowolf [CC BY-SA 3.0 (http://creativecommons.org/licenses/by-sa/3.0/)]

When people visualize asters, this is the variety they most likely think of. New England Asters are often sold in garden nurseries. Its large ray flowers have numerous petals that are usually blue/violet but may also be pink or occasionally white. Its disc flowers change from yellow to purple as a signal to pollinators.

New England Asters are native to Saskatchewan, Manitoba, Ontario, and Quebec. They grow naturally in open spaces, in fields and along the edges of swamps and wooded areas. New England Asters prefer full sun but will tolerate partial shade. They will flourish in dry to moist soils.

Like Heath Asters, New England Asters are a host plant for silvery checkerspot and northern pearl crescent butterflies.

New York Aster (Symphyotrichum novi-belgii formerly Aster novi-belgii)

A single New York aster flower head, purple petals and yellow interior
Image Credit: TeunSpaans [CC BY-SA 3.0 (http://creativecommons.org/licenses/by-sa/3.0/)]

New York Asters are very similar in appearance to New England Asters. Both varieties produce abundant large ray flowers with numerous petals in shades of blue/violet, pink, and occasionally white. The height of New York Asters is dependent on soil conditions. In drier, sandy soils, the plants tend to be short (around 30cm). In rich, loamy soils, the plants may grow as tall as 180cm.

This variety grows naturally in Quebec, Newfoundland, New Brunswick, Nova Scotia, and Prince Edward Island. It prefers damp soil and full sun, often establishing itself near the coast.

Asters are one of the best native plants for a butterfly garden, as all varieties of the flowers attract butterflies and moths. If you’re hoping to attract a specific species of butterfly, cross-check the Carolinian Canada website to see which variety of aster is most likely to entice those butterflies to your garden. Otherwise, just choose the asters that appeal most to you, based on their size and bloom colour, and wait for the butterflies to arrive.

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