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Late Season Blooms for Butterflies

Monarch & Asclepias (Milkweed)
Monarch Butterfly & Asclepias (Milkweed)

One of my favorite aspects of summer is seeing all the butterflies, like exquisitely colorful silk tapestries, fluttering throughout my garden. Butterflies are from the insect family, Lepidoptera, which includes butterflies, skippers and moths. Over 151 species of butterflies have been recorded in the state of Maryland. Many butterflies have names that conjure up images of a land replete with fairies and unicorns; names such as wood nymphs, brushfoots, satyrs, elfins, and duskywings. Butterflies are beautiful, tough yet fragile, and can put a smile on the face of even the most negative nature-averse person on the planet.

Tiger Swallowtails on Joe Pye Weed
Tiger Swallowtails on Joe Pye Weed

Many butterflies have very particular needs throughout their life cycle. Some are very specialized and require a specific host plant family, or sometimes only one particular host plant, to feed on during their larval stage as caterpillars. In addition, some require specific plants that they use as nectar sources; perhaps it is the quality of the nectar, the shape of the flower, the specific bloom time, or simply a nectar plant that tends to grow in the same habitat as the larval host plants and through evolution have become the preferred flowers for nectar consumption simply because they were the closest flowers. Unfortunately, with development systematically encroaching on wild areas, and residential and commercial gardens containing few, if any, native plants, these important food sources, that are essential to the survival of future generations of butterflies, are disappearing quickly. Because of this, many butterfly species have declined and some have even become endangered.

Tiger Swallowtail on Monarda

The good news is that you can help. Homeowners can have a crucial impact on the future of our butterfly population by planting more native plants in their gardens. As this year’s growing season comes to an end, we can help butterflies now by helping them to prepare for winter. Butterflies spend their winter in a variety of ways. Some butterflies, like the famous Monarch, migrate south for the winter, traveling an exhausting, perilous journey across thousands of miles. Other butterflies over-winter as eggs, chrysalis, or caterpillars, hiding under fallen leaves or tucked away on the undersides of branches. Still others, such as the Mourning Cloak, spend the winter as adult butterflies, hiding under the shaggy bark of trees in a state of torpor, or semi-hibernation. But all butterflies share one thing in common, in order to survive the winter; in late summer and early autumn they all need extra energy and nutrition in the form of nectar.

It is no accident that there are many native plants that bloom toward the end of summer. Through hundreds, or even thousands, of years of evolution, flowers adapted their bloom period to coincide with the time when pollinators are available and in need of nectar. Simply put, that means that there are many beautiful flowers to choose from that will suit nearly every gardener’s (and butterfly’s) taste. In order to attract the most butterflies and have a beautiful end-of-season garden, be sure to provide an assortment of native plants that bloom at different times, right up until the end of the growing season. Here is a list of some of my favorites that are easy to find and easy to grow.

[Note on availability from Larry Hurley, Perennials Specialist: Availability of perennials for sale at Behnke Nurseries varies throughout the year, with the best availability from mid-April to early June. Some of the items described below, such as the wild form of Black-eyed Susan, Rudbeckia hirta, I have been unable to find for sale. Vernonia noveboracensis and Conoclinium coelestinum are occasionally but not routinely, available. You can always email me at Contact Us to check availability on perennials you are looking for.]

Joe Pye weed
One of my all-time favorites, and a seemingly infinite source of nectar, is Joe Pye weed (Eupatorium species). Depending on the variety, Joe Pye can grow from a diminutive two feet tall, to an astounding twelve feet tall. The hazy purple-pink flowers are actually umbels of numerous tiny flowers that produce copious amounts of nectar that every butterfly in the neighborhood would have a hard time passing up. Some varieties, such as common Joe Pye weed, Eupatorium dubium, and spotted Joe Pye weed, E. maculatum, require soil that does not dry out. However, trumpet weed, E. fistulosum, can withstand drier soils. In my garden, however, I grow the cultivar, Eupatorium maculatum ‘Gateway’, and the plant does extremely well without any additional water (although I gave it plenty of water the first year until it became established). Joe Pye weed looks fantastic when planted in odd-numbered groups of three, five, or more. Try it with switchgrass, Panicum virgatum, or Indian grass, Sorghastrum nutans, for a stunning late-season effect.

Aster divaricatus
Aster divaricatus

Other late season butterfly favorites are plants in the aster family. Asters are a diverse group of flowering plants that offer fall-blooming beauties for both the sunny and the shady border. The most easy-to-find asters include New England aster, Aster novae-angliae, and New York aster, Aster novae-belgii, both of which prefer full sun to partially sunny areas. These plants are popular in the nursery industry and many cultivated varieties are available with many different flower colors and plant heights to choose from. Asters can come in colors ranging from sophisticated light pink to arresting fuchsia, and from delicate sky blue to dramatic royal purple. Asters are easy to grow, just provide them with a bit of extra attention the first year. Asters also look better when grouped together and glow in the late summer garden when most other plants have petered out. Some varieties bloom late in the fall and the flowers look spectacular among the red, yellow and orange fall foliage. In addition, the non-cultivated varieties of both New England and New York aster are the host plant to the Pearl Crescent butterfly.

Phlox paniculata
Phlox paniculata

Garden Phlox
A third favorite and a must-have for any butterfly garden, is tall garden phlox. There are many cultivated varieties to choose from, but one of my favorites is Phlox paniculata ‘David’. Some phloxes tend to get a bit of whitish mildew on their leaves, but not David. With its five-inch long panicles of pristine white, hay-scented flowers, David can take drought, average garden soil, and whatever else you throw at it.

In addition, if seed heads are left to mature, you will soon find your garden full of David offspring, which tend to revert back to their wild nature and mature to different shades of vivid pink. In addition to ‘David’, ‘Eva Culum’, ‘Franz Schubert’ and ‘Katherine’ are the cultivars that I enjoy growing in my garden, but there are many other varieties to choose from. Phlox begins blooming in July and continues well into the end of August. I find that they are constantly visited by many different butterflies and hummingbird moths.

[Note from Larry Hurley, Perennials Specialist: I have seen powdery mildew on Phlox ‘David’, but all things being equal, it develops fewer symptoms than many of the older selections. Others that are mildew tolerant include ‘Robert Poore’ and ‘Speed Limit 45’. This is the end of the Phlox sales season, so selection at this point is limited.]

Black-Eyed Susan
No butterfly garden would be complete without our state flower, the black-eyed Susan. Rudbeckia hirta and other Rudbeckia species are tough garden plants that deserve their place in every garden. Although it seems that every gas station tends to have these plants, that should just give you more reason to consider planting them because they bloom for long periods of time and are very easy to grow. In addition to being a nectar source, American goldfinches and other seed-loving birds will flock to your flowers, if you let your plants go to seed. It is exciting to watch an American goldfinch clinging upside down from his own weight, carefully picking out the small black seeds. Letting the flowers go to seed also means you will probably be rewarded with additional black-eyed Susan seedlings the following year. As if all that isn’t enough, the uncultivated species, Rudbeckia hirta, is the host plant to the Silvery Checkerspot butterfly.

An important group of plants to consider for feeding butterflies in late summer is the goldenrod (Solidago) genus of plants. Goldenrods are the quintessential nectar producing plants of our area. These plants can take drought, scorching heat, and even overcrowding, and still shine on. Their tiny yellow flowers growing along their slender stems must be an intoxicating source of nectar, because their flowers are never without the company of numerous pollinators. Goldenrods tend to be one of my favorite flowers. There are many different species and cultivated varieties to choose from that offer different shape and sized plants. All are exciting when grouped together with vivid purple asters, showy pink phlox, and smoky violet-pink Joe Pye weed. One of my particular favorites is Solidago rugosa ‘Fireworks’, which really does look like a parade of golden fireworks. But try a number of varieties; they all add sparkle to the flower border.

New York Ironweed
A lesser-known native plant which is a spectacular nectar source is New York Ironweed, Vernonia noveboracensis. This plant can grow up to six feet tall and likes full to part sun. Besides getting a layer of mulch in spring, the ironweed in my garden does not receive any additional water and still looks great. Its luminous purple flowers remind me of little puffs of woolen pompoms. Plant it in groups among black-eyed Susans and goldenrods for a dramatic effect. Purple and yellow are on opposite sides of the color wheel and the contrast of their vivid colors draw the attention of pollinators and people alike. For a more subdued effect, plant purple love grass, Eragrostis spectabilis, or purple muhly grass, Muhlenbergia capillaris, in the front of the border to mimic the purple color and create a more cohesive design. Regardless of what you plant it with, ironweed will look great in your garden.

Although there are many other late-blooming native flowers to write about, I wanted to switch gears and mention a few plants that would work for those homeowners who are blessed with shady areas in their yard. Tolerating excruciatingly hot summer temperatures this year, I have found myself spending more time in the shady parts of my yard which, at ten to fifteen degrees cooler than the sunny areas, are a respite during the summer months. Butterflies, too, enjoy a break from scorching heat and will travel into tree lined gardens in search of native beauties such as cardinal flower and white wood aster. Both of these native plants are late summer bloomers and offer rich nectar for hungry pollinating insects.

Cardinal flower

Cardinal Flower
Cardinal flower, Lobelia cardinalis, is a stunning native wildflower. This plant is always a surprise to most people when they find out that this spectacular flower grows wild in our wooded areas. As its name implies, the cardinal red flowers rival the color of the red robes of the Cardinals in Rome. Larger butterflies, in particular swallowtails, seem to thrive on the nectar from this sensational plant. In addition, hummingbirds flock to the flowers and will fight over the area so that they do not have to share the tasty sweet liquid with any other hummer. I particularly enjoy the combination of cardinal flower in bloom planted with the non-natives Japanese painted fern and Brunnera macrophylla ‘Looking Glass’. The wide silver leaves of Looking Glass and the lacey silver and maroon leaves of painted fern, both compliment and contrast with the bright crimson of cardinal flower. And since cardinal flower can sometimes be a little leggy, underplanting Brunnera and ferns in front of cardinal flower will hide the cardinal flower’s lanky stems. Another excellent companion plant and a favorite of pollinators is a native called blue mistflower, Conoclinium coelestinum (formerly Eupatorium coelestinum.) Looking very similar to the annual blue ageratum, but much taller, the Wedgwood blue fuzzy flowers of blue mistflower create a striking vignette with cardinal flower.

Wood Aster
By contrast, white wood aster, Eurybia divaricatus (formerly Aster divaricata), is a sophisticated subtle beauty. When in bloom, white wood aster plants nearly exhaust themselves by completely covering their stems with tiny white blossoms held high above glossy heart-shaped leaves. Since flowers are modest in size, white wood aster creates a stronger impression when planted in larger groups. Add white wood aster to your vignette of cardinal flower, Brunnera Looking Glass, Japanese painted fern, and blue mistflower. Throw in a few Christmas ferns for some deep green to tie in the color scheme and allow the eye to rest, and you have a shady border that will be the envy of the neighborhood. For a bold background to offset the dainty blooms and lacey foliage, plant some Annabelle or White Dome hydrangeas, which will, by this time, have lime green flower heads. Now you’ve taken the shady border to an entirely new level of ‘Wow’.

So the next time you decide to add some more plants to your garden, consider adding a variety of late season nectar sources for the butterflies. The colors of the flowers and the color and movement of the butterflies will bring you endless joy during the final days of summer.

Sidebar From Behnke’s Woody Plant Manager, Miri Talabac. Several native shrubs also serve as great nectar sources for butterflies and other pollinators. Sweetspire, Summersweet, Buttonbush, New Jersey Tea, several deciduous Azaleas are some of the most popular. (As with the perennials, some of these plants are more readily available in spring.)

Tiger Swallowtail photos by Natalie Brewer.  Photos by Larry Hurley:  Monarch with Milkweed, Phlox paniculata,  Solidago ‘Fireworks’, Aster divaricatus, and Solidago with Joe Pye. Cardinal Flower photo credit.

by Natalie Brewer, Master Gardener

Stephanie Fleming was raised at Behnke’s Nurseries in Beltsville. Her Mom, Sonja, was one of Albert & Rose Behnke’s four children. She was weeding from the moment she could walk and hiding as soon as she was old enough to run, so many weeds, so little time. Although she quickly learned how to pull out a perennial and get taken off of weed pulling duty.

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