What is a Keystone Plant?

Simply put, it is an indigenous species that plays a crucial role in the local food web. It interacts with many other species, supporting native microbes, insects, birds, and other animals with significant resources, such as food and habitat. These resources attract pollinators and herbivores. In turn, these insects support other animals higher up on the food chain, like birds and mammals. These native plants also serve as pillars in the structure, integrity, and function of an ecosystem. They help to regulate nutrient cycling, soil health, and water availability.

The loss or decline of a keystone plant species can lead to significant changes in the ecosystem and potentially cause the decline of the other species that depend on it. With the loss of native habitats due to climate change and development, it’s up to people to take action. According to Dr. Tallamy, “Gardeners need to recognize that their little piece of the world is part of the future of conservation.” And he sees that recognition as empowering. One person can shrink their lawn. One person can remove their invasive plants. And, perhaps most notably, one person can put in keystone plants. Adding these massive ecological boons to cultivated landscapes will make a positive impact.

NOTEWORTHY SELECTION:
Sweet birch offers tremendous wildlife value and aesthetic appeal throughout the year

Name: Betula lenta

Zones: 3–8

Size: 60 to 80 feet tall and 35 to 45 feet wide

Conditions: Full sun to partial shade; dry to moist, well-drained soil

Native Range: Eastern North America

Few things bring me as much joy as observing the mourning cloak butterfly in late winter and early spring each year. Perhaps the earliest butterfly to appear in the Northeast, this charismatic insect overwinters as an adult, but needs host plants like sweet birch to rear the next generation. In fact, this birch is an incredibly beneficial keystone plant that is a host to a staggering 284 species of butterflies and moths, alongside its countless connections with other insects, mammals, and birds.

From a landscape perspective, sweet birch is no slouch. It’s a fast-growing tree that can eventually reach up to 80 feet tall and features gorgeous, silvery, plate-like bark when mature. In fall, this tree delivers a beautiful display of amber-gold foliage. Before the leaves emerge, the branch tips drip with brown catkins in spring. Scrape a little bark away from a small branch and inhale, and you will smell the delicious wintergreen aroma of the oil that emanates from the wound.

I have found sweet birch to be quite drought tolerant once established, but it will grow in average to moist soils as well. As a young sapling, this species is not especially shade tolerant, so be sure to plant your tree where it will receive a half day of sunlight or more. Its excellent autumn color pairs well with other trees and shrubs with red or orange fall color such as flowering dogwood (Cornus florida, Zones 5–9) and black chokeberry. With such tremendous wildlife value and aesthetic beauty in all seasons, I rank this tree as a top keystone species for Northeast gardens and landscapes.

Black chokeberry (Aronia melancarpa, Zones 3–8)

Wild bergamot (Monarda fistulosa, Zones 3–9)

| The Expert |

Uli Lorimer, author of Northeast Native Plant Primer: 235 Plants for an Earth-Friendly Garden, is director of horticulture for the Native Plant Trust—a nonprofit organization dedicated to the preservation of the native flora of the Northeast U.S.

NOTEWORTHY SELECTION:

Don’t overlook white pine for its beauty, fragrance, and food chain contributions

Name: Pinus strobus

Zones: 3–8

Size: 50 to 80 feet tall and 20 to 40 feet wide

Conditions: Full sun to partial shade; moderately moist, well-drained soil

Native Range: Eastern North America

When considering my favorite keystone plant species, white pine always makes my list. Many people are familiar with this humble conifer as it’s part of our daily lives, lining highways and corner lots. But this amazing tree adds more to our gardens and neighborhoods than a green wall. Its generous size makes it a fantastic specimen that gives relieving shade for people and shade-loving species, while its green to blue-green hues provide lovely winter interest. During the growing season, it also attracts an enjoyable show of butterflies, birds, and small mammals.

And that beautiful pine fragrance really gets me every time. It immediately takes me back to hot summer days, when the scent intensifies, making the world smell like a rich forest bursting with life. Terpenes are the chemical compounds responsible for the scent, providing nutrients to insects and, throughout human history, to the people who learned to make a vitamin-rich spring tonic from the leaves to relieve long winter diets devoid of vegetables. This tree is so entwined with the people who call the eastern temperate forests home that it’s known as a sacred tree of peace to the Haudenosaunee. It was instrumental in the prevention of scurvy for seafarers, and it became a light and versatile timber for the construction of homes and railroads.

The white pine’s history aside, it’s an easy-to-grow tree and usually establishes itself effortlessly. It starts life growing quickly, then slows as it builds bulk until reaching more than 100 feet in the wild. With its long lifespan of 250 years, it’s considered a wonderfully reliable tree and a solid foundation for many ecosystems—providing wildlife with food and habitat. Dr. Tallamy has recorded more than 200 caterpillar species that feed off the native pines of the eastern U.S., a service that resounds throughout the food chain.

Slender mountain mint

(Pycnanthemum tenuifolium, Zones 4–8) 

New York ironweed

(Vernonia noveboracensis, Zones 5–9)

| The Expert | 

Amy Highland is curator at the United States Botanic Garden. Nearly two decades of public garden experience has provided her with a wealth of knowledge on North American native plants.

NOTEWORTHY SELECTION:

Eastern gray goldenrod is a bright addition to perennial plantings

Name: Solidago nemoralis

Zones: 3–9

Size: 6 to 24 inches tall and wide

Conditions: Full sun to partial shade; average, dry to moderately moist, well-drained soil

Native Range: Eastern to Southwestern North America

No list of garden-worthy keystone plants would be complete without a goldenrod (Solidago spp.). The genus Solidago contains species native to every eco-region in North America. In the Southeast, Eastern gray goldenrod is one of my favorites. It’s among the shorter species of goldenrod, growing under 3 feet tall and making it ideal for most garden settings. It flowers between midsummer and early fall in our area with abundant bright yellow panicle (tight clusters of numerous tiny flowers) blooms on the upper side of its unbranched stalks.

Eastern gray goldenrod gets its common name from the downy hair on the stems resulting in a gray-green hue. This keystone species supports 104 butterfly and moth species and 42 specialist native bees, the top in its perennial class for our region. Goldenrods are often mistaken for the common allergen ragweed, but this bee-pollinated species is unlikely to cause allergies.

This plant does best with full sun in dry conditions, but it will also tolerate shade. It does fine in average soil. Leaving stems in the landscape beyond the flowering period is beneficial for overwintering insect larvae and also provides winter interest, as the fluffy, white seed plumes are quite pretty when backlit. Letting the plants go to seed will also result in more plants to enjoy in future years.

I additionally love Eastern gray goldenrod for its multiple uses in the garden. It’s perfect for short meadows, sunny perennial gardens, and cut flower arrangements. It pairs beautifully with fall-blooming blue asters (Symphyotrichum spp. and cvs., Zones 3–9) and purple narrowleaf ironweed (Vernonia lettermannii, Zones 4–9).

Maryland goldenaster

(Chrysopsis mariana, Zones 4–9)

Elliott’s blueberry

(Vaccinium elliottii, Zones 5–9)

| The Expert | 

Heather Alley is a conservation horticulturist at the State Botanical Garden of Georgia at the University of Georgia (UGA), where she earned her master’s degree in horticulture.

NOTEWORTHY SELECTION:

Allegheny serviceberry delivers multiseason
interest from blooms to berries

Name: Amelanchier laevis

Zones: 4–8

Size: 15 to 25 feet tall and wide

Conditions: Full sun to partial shade; average, moderately moist, well-drained soil

Native Range: Eastern to Central North America

When it comes to powerhouse keystone plants, the aptly named Allegheny serviceberry excels at providing a wide variety of services for pollinators, birds, and people. A member of the rose family, it offers pollen for early emerging native bees, beneficial pollinating flies, and even beetles. Amelanchier foliage is utilized by 124 species of caterpillars, including the red-spotted purple butterfly and striped hairstreak butterfly, and small-eyed and blinded sphinx moths.

The pure white blooms appear before most other flowering trees, making this woody a true harbinger of spring. Adult butterflies and hummingbirds will also visit the flowers for nectar on warm spring days. The sweet purplish-red berries that follow the blooms are nutritious and make fantastic jams and jellies—if you can beat the birds!

Avoid planting Allegheny serviceberry in heavy clay, damp, or wet soils, as this species is not tolerant of poor aeration to its roots. Native to the Upper Midwest, Great Lakes, Northeast, and Appalachians, it’s tolerant of winter cold and summer heat. During periods of high humidity and warm temperatures, Amelanchier species are susceptible to leaf rust, powdery mildew, and fire blight. Fall webworm can form large colonies similar in appearance to tent caterpillars in late summer and early fall, but they seldom do significant damage to healthy trees.

Allegheny serviceberry is a handsome large shrub or small tree that typically grows with multiple stems and an open and broad-spreading form. It can be pruned and trained to grow as a single-stemmed tree with a more columnar shape, if desired, but this is not typical of the species. Either way, it has the perfect stature for smaller-sized gardens and deep foundation plantings.

Butterfly weed (Asclepias tuberosa, Zones 3–9)

Smooth aster (Symphyotrichum laeve, Zones 3–8)

| The Expert | 

Neil Diboll holds a BS in environmental sciences from the University of Wisconsin and is president of and consulting ecologist for mail-order Prairie Nursery in Westfield, Wisconsin. He is also a frequent speaker and the coauthor of The Gardener’s Guide to Prairie Plants.

NOTEWORTHY SELECTION:

Sulphur buckwheat creates a pollinator’s paradise in rugged terrains

Name: Eriogonum umbellatum

Zones: 4–8

Size: 6 to 12 inches tall and 12 to 36 inches wide

Conditions: Full sun; dry, well-drained soils

Native Range: Mountain West of North America

In early summer, when Mountain West wildflowers are going petal to the metal, there’s one plant that deserves more exploration, whether in the wild or in a landscaped setting. The buttery yellow, orb-shaped clusters of flowers of sulphur buckwheat can reward you with not only a beautiful floral display but also an abundance of pollinator activity. As a keystone plant of rugged and rocky terrains, it thrives in full sun and well-drained locations. It is a caterpillar host plant and nectar resource for over 65 species of butterflies and moths, and a nectar and/or pollen source for bees, beetles, wasps, and flies.

Sulphur buckwheat is a hardy plant that is low in stature, growing as round mats of small, leathery, green, spatula-shaped leaves with silvery undersides. The flowers bloom on short, leafless stalks rising 4 to 12 inches above the plant. As the long-lasting blooms age, they shift
in color from yellow to a pretty rust, and the green and silver leaves turn red in fall, adding late-season color.

This perennial works nicely as an accent plant placed in or around stones and boulder features, or along pathways and edges. The leaves persist through winter, providing year-round interest and protection for overwintering beneficial insects, such as lady beetles. Adequate water is needed as the plant becomes established, but then it becomes a very low-maintenance selection that stays self-contained and thrives without much fuss. With luck, a dotted-blue butterfly will show up to drink nectar after feeding on the plant as a caterpillar (and may even use the plant to host next year’s larvae).

Silvery lupine (Lupinus argenteus, Zones 4–9)

Scarlet globemallow (Sphaeralcea coccinea, Zones 3–8)

| The Expert | 

Steve Armstead works in Colorado as a pollinator- conservation and nature-based climate-solutions specialist
for the Xerces Society for Invertebrate Conservation. He
coauthored the Colorado Native Pollinating Insects Health Study, an assessment and management-practices plan for conserving pollinators.

NOTEWORTHY SELECTION:

Maximilian sunflower offers a myriad of wildlife benefits while providing enchanting blooms on a unique form

Name: Helianthus maximiliani

Zones: 4–9

Size: 3 to 10 feet tall and 2 to 4 feet wide

Conditions: Full sun; poor to average, dry, well-drained soil

Native Range: Central and Southwest North America

If you’re looking for a keystone native with bloom appeal, you can’t go wrong with Maximilian sunflower. It’s absolutely stunning. Compared to the more well-known common sunflower (Helianthus annuus, annual), Maximilian is altogether more delicate. Its leaves are slender, long, and folded slightly along the midvein. The flowers have longer petals and a lighter colored, smaller center. Each plant grows as a tall single stalk with many blooms along the stem. The tall, thin form allows the plant to sway gracefully in the wind, adding to its beauty. It’s a perennial sunflower native to the majority of the U.S. In the Southwest, it is native to parts of Texas, Oklahoma, California, and New Mexico.

There are over 60 species of Helianthus native to North America, providing a bounty of benefits to each native microclimate. Maximilian sunflower gives shelter and habitat to visitors ranging from small bees nesting in the stems, to birds seeking shelter in the leaves. Each large sunflower bloom supplies ample nectar and pollen to a wide variety of pollinators before creating large seeds at maturity. The seeds are favorites among grain-eating birds and mammals. The leaves are palatable to deer and livestock, adding yet another benefit.

In the garden, this fall bloomer creates a spectacular border planting with a height reaching 10 feet. For a shorter stature, prune the sunflowers to the ground in mid-spring, limiting the height closer to 4 feet. This tallgrass prairie native is drought tolerant and thrives in poor but well-drained soils. In fact, poor soils yield more upright plants. Maximilian sunflowers spread, but if this is not desired, they are easily transplanted.

Blue grama (Bouteloua gracilis, Zones 3–10)

Banana yucca (Yucca baccata, Zones 4–9)

| The Expert |

Amy Galloway-Medley is a horticulturist at the Lady Bird Johnson Wildflower Center in Austin, Texas. She is also an ISA certified arborist and earned a bachelor of applied science degree, with an emphasis on plant and soil systems, from Louisiana State University.

NOTEWORTHY SELECTION:

Chokecherry is an adaptable small tree that wows with flowers, fruit, and fall foliage

Name: Prunus virginiana

Zones: 2–8

Size: 10 to 30 feet tall and 10 to 20 feet wide

Conditions: Full sun to partial shade; dry to moist, well-drained soil

Native Range: North America

Native Prunus species are keystone plants in many eco-regions, supporting high numbers of butterflies and moths that use this genus as both adult and larval food sources. Chokecherry, named for its bitter but edible, showy stone fruits, is my top pick for providing Pacific Northwest gardeners with a fast-growing, adaptable shrub to small tree that ranges widely throughout the
region and the continent.

A handsome ornamental, its elongated clusters of creamy white flowers bloom between late spring and midsummer, attracting beneficial insects and native pollinators, such as bees, butterflies, and hummingbirds. While its bright red to dark purple fruits should be cooked or dried and have their seeds removed to be safely edible to humans, birds relish them as is. This plant is an important food source for a diverse array of wildlife. Hardy and deciduous, in fall its leaves add colorful hues of red, orange, and gold to the landscape, as well as overwintering habitat for helpful insects, and nutrients to the soil when they decay into organic matter.

Chokecherry occurs in many habitat types and is thus adaptable to a variety of conditions and soils. It’s both heat and drought tolerant, though it benefits from moisture and afternoon shade in arid areas. Gardeners should be prepared to water this plant deeply for the first year or two while it gets established, and occasionally remove the suckers, particularly if a single-trunked specimen is desired. Once established, chokecherry grows quickly, adding beauty and biodiversity to just about any garden, landscape, or pollinator and wildlife habitat planting. Its thicket-forming tendencies are especially useful for hedgerows and bank stabilization.

Blue blossom (Ceanothus thyrsiflorus, Zones 5–9)

Seaside daisy (Erigeron glaucus, Zones 5–8)

| The Expert | 

Kristin Currin is coauthor of The Pacific Northwest Native Plant Primer: 225 Plants for an Earth-Friendly Garden. She has been ethically propagating native plants in the Pacific Northwest for many years. Her nursery in Mosier, Oregon, Humble Roots Nursery, has provided gardeners and conservation groups with native plants to support local biodiversity.