The Connection Between Native Plants and Insects
Native plants are critical to the survival and vitality of our local ecosystems. Renowned entomologist Dr. Douglas Tallamy wrote the book “Bringing Home Nature,” in which he describes how the use of non-native plants in landscaping, sound the alarm about habitat and species loss.
Plants (and algae) are at the base of every food chain because they produce their own food using the sun’s energy. As plants have evolved, they have developed numerous defenses to keep from being eaten. Herbivores (insects that eat plants) that evolved along with those plants have evolved the ability to overcome those defenses. This is important because if herbivores can’t eat the plants, then they can’t survive, and if they don’t survive then there will be little food for organisms.
The most important herbivores are insects simply because they are so abundant and diverse and, thus, are a major food source for species. The problem is as Tallamy learned, “most insect herbivores can only eat plants with which they share an evolutionary history.” Insects are specialized as to which plants they can eat because they have adapted ways to overcome the defenses that said plants have developed to keep things from eating them. Healthy, abundant, and diverse insect populations support biodiversity, but such insect populations won’t exist without a diverse community of native plants with which the insects share an evolutionary history.
That is essentially the thesis of Tallamy’s book. In a chapter entitled “Why Can’t Insects Eat Alien Plants?” Tallamy expounds on the specialized relationships between plants and insects that have developed over millennia. Plants introduced from other areas have not formed such relationships and are thus used to a much lesser degree than their native counterparts. Research concerning this topic was scarce at the time this book was published, but among other studies, Tallamy cites preliminary data from a study he carried out on his property. The study compared the insect herbivore biomass and diversity found on four common native plants vs. five common invasive plants. The native plants produced 4 times more herbivore biomass and supported 3.2 times as many herbivore species compared to the invasive plants. He also determined that the insects using the alien plants were generalists, and when he eliminated specialists from the study, he still found that natives supported twice as much generalist biomass.
Apart from native plants and insects, Tallamy frames much of his argument around birds. Birds have been greatly impacted by humans. Their populations are shrinking at an alarming rate, and many species are threatened with extinction. Tallamy asserts, “We know most about the effects of habitat loss from studies of birds.” We have destroyed their homes and taken away their food and “filled their world with dangerous obstacles.” Efforts to improve habitat for birds will simultaneously improve habitat for other organisms. Most bird species rely on insects during reproduction in order to feed themselves and their young. Reducing insect populations by filling our landscapes largely with alien plant species threatens the survival of many bird species.
Tallamy profiles 20 groups of native trees and shrubs that excel at supporting populations of native arthropods and then describes a whole host of arthropods and arthropod predators that birds love to eat. He goes on to explain why biodiversity is so essential for life on Earth, and how the cost of using Alien Ornamentals and our obsession with exotic plants has caused problems for us in our natural areas. An example is the pupa of ladybird beetle on white oak leaf and why oaks importance in supporting both vertebrate and invertebrate wildlife cannot be overstated.
Convincing people to switch to using native plants isn’t always easy, especially if your argument involves providing habitat for larger and more diverse populations of insects. For those who are not fans of insects, Tallamy explains that “a mere 1%” of the 4 million insect species on Earth “interact with humans in negative ways.” The majority are not pests. It is also important to understand that even humans “need healthy insect populations to ensure our own survival.” Tallamy also offers some suggestions on how to design and manage an appealing garden using native plants.
The Origins and Loss of Native Species
Native plants evolved in the Americas and were growing just fine long before “we” laid our heavy hands on the terra firma. The use of native pollinator species once made this land a rich source of life for its indigenous peoples and, later, for European colonists and their descendants. That is no longer the case. Today, most of the surviving remnants of the native flora that formed them have been invaded by alien plants. Europeans first fell in love with the exotic beauty of plants that evolved on other continents when the great explorers returned home with beautiful species no one had ever seen before. It quickly became fashionable and a signal of wealth and high status to landscape with alien ornamentals that no one else had access to. As the first foreign ornamentals became more common in the landscape, the motivation to seek new alien species increased. Even today, the drive to obtain unique species or cultivars is a primary factor governing how we select plants for our landscapes. In other words, most of the surviving remnants of the native flora that formed them have been invaded by alien plant species.
Native plants are well adapted to their particular ecological niche and so are often far less difficult to grow than species from other altitudes, latitudes, and habitats. Islands of small, strategically placed and connected patches of completely restored habitats might foster the survival of some of our wildlife, but will only protect a small number of the species that once thrived in North America. We simply have not left enough intact habitat for most of our species to avoid extinction. All species need space in order to dodge the extinction bullet. The transition from alien ornamentals to native species will require a profound change in our perception of the landscaping value of native ornamentals.
FYI - A native plant in the U.S. is defined as one that was naturally found in a particular area before European settlement. Native plants are the foundation of a region’s biodiversity, providing essential food sources and shelter for birds in a changing climate. They are adapted to local precipitation and soil conditions.
Native plants tend to grow vigorously without requiring much fussing. They generally take climatic extremes in stride. Most are major attractions for butterflies, birds, bees and other pollinators because they provide shelter for these beneficial garden visitors. In my community garden there are native bumblebees, but their numbers are diminishing due to pesticides, increasing pressures on wildlife populations and the loss of open-pollinated true native species. Add on the loss of biodiversity and habitats, pollution and climate change. Combined, they threaten two-thirds of all birds and insects. Our livable world is facing serious threats as one of every three bites of food relies on pollinators.
-Just look at the Western bumblebee which faces a ninety-three percent extinction rate. The United States continues to allow Big Polluters to drive bumblebees, monarch butterflies and countless other pollinators to the brink of mass extinction.
-Monarch butterflies have declined by 90 percent in the last 20 years due to the loss of milkweed. The key culprit is the massive increase in the use of glyphosate -- a.k.a. Monsanto’s Roundup, a common pesticide sold in hardware stores. Bayer-Monsanto is allowed to sell lethal chemicals that push our pollinators closer to extinction. Roundup kills many other pollinators.
-We spray more than 1 billion pounds of lethal pesticides like neonics every year, even after other countries banned them due to clear links to mass pollinator deaths and harm to human health.
As a gardener, you can increase your love of plants and nature by planting pollinator native plants. For the first time in history, gardening has taken on a role that transcends the needs of the gardener. They now have become important players in the management of our nation's wildlife and can make a difference in the future of biodiversity by growing native plants.
I’ve been an organic gardener for 35 years and for the past five years, I’ve been growing native pollinators at the Tommy Thompson Community Garden in Burlington, Vermont including New England asters, phlox, coneflowers, bee balm, milkweed, and butterfly bush. The flowers from the butterfly bush attract hummingbirds because of its high nectar count. Additionally, they are drawn to the long, brightly colored spikes resembling lilacs. Milkweed, an old-fashioned perennial attracts pollinators like Monarch butterflies also known as the “milkweed butterfly.” One of the hottest trends in gardening is sustainable landscaping using native pollinator plants. Schools are incorporating this way of gardening into learning because it’s a way of teaching responsibility and healthy choices in our world of climate disruption. So why not grow a pollinator garden? Every little bit helps.
*The Saving America’s Pollinators Act of 2021 would ban all toxic pesticides and grant essential pollinators, and our food system, a chance at survival.
Are Native Cultivars as Valuable as True Native Species?
Annie White, a PhD student at the University of Vermont, under the guidance of Dr. Leonard Perry is addressing the question - Are native cultivars (nativars) as valuable in pollinator habitat gardens as true native species? Many plants marketed as “natives” in garden centers have never grown naturally in the wild. The word cultivar means a cultivated variety; thus, a cultivar is selected and cultivated by humans. It’s called a nativar.
As initiatives to address pollinator decline are becoming widespread this is an important question to answer, and especially because cultivars (nativars) are more readily available in the nursery trade. White started her data collection in 2013, utilizing two research sites she established in Vermont. Her research is timely as it includes information on native bees, honey bees, and other pollinators facing serious challenges. She has been studying 14 flowering perennial plants that are native to the Northeast, comparing each to a native cultivar. In the case of Echinacea purpurea, three cultivars were studied.
White has done years of groundbreaking field research. She found that while many cultivars have been bred for enhanced bloom, color, or other characteristics, they do not have the same ecological benefits as do straight species plants. She found that seven native species were visited significantly more frequently by all insect pollinators (combined) than their cultivar. Four were visited equally, and one native cultivar was visited more frequently than the native species. Some native cultivars may be comparable substitutions for native species in pollinator habitat restoration projects, but all cultivars should be evaluated on an individual basis.
Several studies suggest that wild bees prefer to forage, but not necessarily exclusively - on the nectar and pollen from native plants. Native species plants are also typically well-adapted to local soil, climate, and other environmental conditions, making them more durable in the landscape. For these reasons, native species plants are frequently recommended for pollinator habitat restoration and pollinator garden projects.
Of the 13 pairs of plants White compared, seven of the native cultivars attracted significantly fewer bee pollinators than the species. These were ‘Strawberry Seduction’ yarrow, ‘Corbett’ columbine, ‘Twilite Prairie Blues’ baptisia, three coneflower cultivars (‘Sunrise Big Sky’, ‘Pink Double Delight’, and ‘White Swan’), ‘Moerheim Beauty’ Helen’s flower, ‘Alma Poetschke’ New England aster, and ‘Red Grape’ spiderwort.
The five pairs in which there was no difference in bee attraction included ‘Golden Jubilee’ anise hyssop, ‘Hello Yellow’ milkweed, ‘Fried Green Tomatoes’ cardinal flower, ‘Husker Red’ penstemon, and ‘Claire Grace’ bee balm. ‘Lavender Towers’ Culver’s root attracted more bees than the species. The message so far from Annie’s research (pollinatorgardens.org) is that bee preference for cultivar or species will vary with the plant but, in general, native species are a better bet.
If all these lists and research results seem a bit overwhelming, you might start with Annie’s ten top plants. These are herbaceous perennials that are native to the Northeast, attract a diversity of pollinator species, and perform well and look good in-home landscapes. They are the blue giant hyssop, purple coneflower, trumpet honeysuckle, sundial lupine, Helen’s flower, Culver’s root, foxglove beardtongue, Joe-pye, New England aster, and wild bergamot.
Genetic variety is the foundation for biodiversity, which is the foundation for healthy ecosystems. Open-pollinated, straight species natives provide this genetic diversity; native cultivars do not. Finding locally grown straight species natives, is another key to supporting local ecosystems.
Besides diminishing the genetic pool, a sterile cultivar that does not produce seeds, will not feed seed-eating birds. It gets trickier when we start to factor in pollinators. We can often see which plants attract more insects, but that is the tip of the ecological iceberg. The flowers of native cultivars (nativars) may vary from the native species in size, shape, abundance, color, and bloom time—all attributes known to influence pollinator visitation. In addition to floral traits, native cultivars are sometimes selected for disease resistance, and more predictable sizes and shapes than their wild relatives, making them more desirable landscape plants. But native cultivars can also be less hardy and may prefer different soil moisture and fertility than the species, and most serious of all, may not be as attractive and useful to pollinators.
When you visit large wholesale growers, retail nurseries, or big box stores, the selection of native plants may be quite limited, and often a cultivar may be your only option. This is troubling, since it seems like the same cultivars of the same plants are offered absolutely everywhere. So much for genetic diversity! The use of strongly selected cultivars is generally discouraged in ecological restoration projects because native cultivars are widely available and widely used in the landscape industry. In fact, when gardeners visit their local garden centers, it’s often impossible to find true native species.
Native plants also tend to grow vigorously without requiring much fussing. They generally take climatic extremes in stride. Most are major attractions for butterflies, birds, bees and other pollinators because they provide shelter for these beneficial garden visitors. The numbers of native bumblebees are diminishing due to pesticides, climate change and the loss of open-pollinated true native species.
FYI - Pollinators and Carbon
Native pollinators increase the nutrient cycling of soils, which help to maximize the forages for both pollinators and grazers alike, thus creating more nutrient dense forages for grazers, and in turn more nutrient dense meats for human consumption. Larger more diverse forages equates to deeper roots, a broader spectrum of nutrients cycled and better atmospheric carbon sequestration rates per acre.
Lists of Pollinator Plants in Vermont
Annie White of the Univeristy of Vermont is currently researching:
Blue Giant Hyssop
‘Golden Jubilee’ Hyssop
Wild Columbine `Corbett’
‘Hello Yellow’ Butterfly Weed
New England Aster
‘Alma Poetschke’ New England Aster
Wild Indigo/Blue False Indigo
Baptisia ‘Twilite’ Prairie Blues False Indigo
‘White Swan’ Coneflower
Echinacea ‘Sunrise Big Sky ’Coneflower
Echinacea purpurea ‘Pink Double Delight’
‘Moerheim Beauty’ Sneezeweed
Lobelia cardinalis Cardinal Flower
Lobelia cardinalis ‘Fried Green Tomatoes’ Cardinal Flower
Wild Bergamot/ Bee Balm
Monarda fistulosa ‘Claire Grace’ Wild Bergamot/ Bee Balm
Penstemon digitalis ‘Husker Red’ Beardtongue
Rudbeckia fulgida Black-eyed Susan
Rudbeckia fulgida ‘Goldsturm’ Black-eyed Susan
‘Red Grape’ Spiderwort
‘Lavender Towers’ Culver’s Root
Full Circle Gardens
In an effort to provide for extended bloom late into the season, a variety of plants were chosen, with many forms of coneflower, Black-Eyed Susans, and asters to attract insects. The goal is to have plants form large clumps to create drifts, intermingling stems and foliage. No soil supplements or mulch are used, and the beds are organically maintained. Below is a partial list of plants, many supplied by Full Circle Gardens, a nursery in Essex which offers a wide selection of native plants and cultivars.
Amsonia tabernaemontana (bluestar)
Asclepias tuberosum (butterfly weed)
Penstemon digitalis (hairy beardtongue)
Thermopsis caroliniana (Carolina lupine)
Lonicera sempervirens 'Major Wheeler' (honeysuckle)
Helenium autumnale (sneezeweed)
Rudbeckia fulgida var. fulgida (Black Eyed Susan)
Rudbeckia subtomentosa 'Henry Eilers' (sweet coneflower)
Symphyotrichum novae-angliae (New England aster)
Echinacea paradoxa (yellow coneflower)
Panicum virgatum 'Shenandoah' (switchgrass)
Schizachyrium scoparium (little bluestem)
-For a complete list of native pollinators, go to Jane Sorensen at River Berry Farm in Fairfax, Vermont. Go to - Pollinator Plants at River Berry Farm www.riverberryfarm.co. Her website is Northeast Pollinator Plants or NEPP. She’s been growing and selling pollinator plants on her family farm in northwest Vermont since 2012. The plant selections for the New England and New York regions have been largely developed from data provided by Xerces Society, and are made available on the Lady Bird Johnson Wildflower Center website.
Vermont Native Pollinators
Really early, when little else is out, is the marsh marigold (yellow), particularly adapted as its name indicates to wet areas. Other early perennials are the wild sweet William phlox (pink to lavender), wild geranium (pink), and the Canada white violet (white with streaking).
Late Spring & Early Summer
red columbine (red and yellow), harebell (blue), water avens (purplish red), blue flag iris (blue purple), narrow-leaf blue-eyed grass (blue purple), red trillium (red), and golden zizia (yellow).
May and June Blooms - downy serviceberry (white flowers), chokecherry (white), and American basswood (yellow). A couple of large shrubs for later bloom are the bunchberry dogwood (white) and staghorn sumac (yellow green). American witchhazel is a shrub with fall blooms (yellow). Other native trees you might consider for pollinator habitat enhancement, such as serving as larval hosts, are birches, American beech, and both white and red oaks.
Some shrubs recommended for pollinators by the Xerces Society include highbush blueberry (white or pink flowers) and pussy willow (yellow or green) for early bloom. Among those for mid-season are ninebark (white) and New Jersey tea (white). For late season consider buttonbush both for flowers (white) and as a larval host.
Late Summer & Fall
Black locust is a good example of a native plant that blooms late. Bees love the flowers, which are gorgeous when in bloom. Others late bloomers include turtlehead (white), flat-topped aster (white and yellow), Joe-pye weed (lavender pink) and boneset (white), swamp milkweed (pink), wild bergamot (lavender pink to violet blue), beardtongue (white), cardinal flower (red), the common native black-eyed Susan (yellow, dark brown center), calico aster (white and pink), New England aster (purple), and goldenrods (yellow).
In a Delaware study by Doug Tallamy on best bets to attract moths and butterflies (www.bringingnaturehome.net), goldenrod attracted the most species ) with asters a close second.
P.S. -The wastefulness of lawns populated with alien grasses demand high-nitrogen fertilizers, broad-leaf herbicides, and pollution-belching mowers. Ornamental grasses like little bluestem, switchgrass and prairie dropseed combine with asters and other late season stalwarts to support bees and other wildlife.
Definitions: Native Plants, Straight Species Versus Cultivars
A native plant in the U.S. is defined as one that was naturally found in a particular area before European settlement. Native plants are the foundation of a region’s biodiversity, providing essential food sources and shelter for birds in a changing climate. They are adapted to local precipitation and soil conditions.
A native plant or straight species occurs naturally in a given location or region. It is a plant that is found in the wild and has not been grown to produce specific ornamental traits. It has evolved naturally in the wild and reproduces via open pollinated seed (wind-blown or insect produced pollination without the help of humans). The straight species of Purple Coneflower is Echinacea purpurea.
The growing demand for native plants in ecological landscaping, including pollinator habitat gardens, has led to the selection and breeding of native cultivars. A native cultivar or “nativar” is a cultivated variety of a native plant, that has been selected by humans (in nature or through repeated selections in a breeding program), cross-bred, and/or hybridized by botanists and plants breeders seeking desirable characteristics that can be maintained through propagation.
A native cultivar (nativar) is a plant that results when native parent plants are used to create a new cultivar. In the case of one parent, a plant breeder might select and propagate one plant that has an especially unique trait, like brighter colored flowers, out of a hundred seedlings sown from a native species. Other traits that humans find attractive in native cultivars, such as a double flowers or an unusual color, may make the flower less attractive to pollinators, and furthermore, may decrease the quantity, quality, and accessibility of the nectar and pollen rewards.
A nativar is sometimes a natural variant that has been found in the wild and brought into cultivation, but often it has been developed by a plant breeder and would never be found in nature. Echinacea purpurea 'Magnus' is a cultivar, a plant that has been selected by horticulturists. A native cultivar is a plant that is produced and maintained by horticulturists but does not produce true-to-seed; whereas a variety is a group of plants within a species that has one or more distinguishing characteristics and usually produces true-to-seed.