Battling Buckthorn

Wisconsin gardening comes with many obstacles: rabbits, deer, cold winters, and invasive non-native plant species. In the war against invasive plants, one of the worst enemies is Buckthorn, specifically Common Buckthorn (Rhamnus cathartica) and Glossy Buckthorn (Rhamnus frangula). Many times we’ll be at a customer’s site and they want to know what the shrubs are creating a screen on the edge of their property. More often than not it’s Buckthorn. Probably the worst example we’ve seen is someone’s neighbor nicely pruned their Buckthorn and hung twinkling lights on it to enjoy from the deck. The tree was the source of loads of Buckthorn seedlings every year.

So what’s the big deal about Buckthorn anyway? Europeans brought Buckthorn over to use for hedges and screening. It grows fast, has hardly any maintenance (unless you want to get rid of it), is easily sheared into a hedge, and rabbits and deer don’t eat it. Unfortunately, it’s one of Wisconsin’s most damaging invasive plants. Read more about Glossy Buckthorn (sewisc.org).

Problem #1: Buckthorn can quickly establish in full sun or shade – it doesn’t care. This aggressive plant will push out native plants, especially in the understory of forests where native plants don’t receive enough sunlight to thrive. We have seen more Buckthorn popping as Ash trees are being lost to Emerald Ash Borer. The greedy buggers will gladly move into the spaces that Ash trees leave behind, swallowing up the landscape.

Problem #2: Female plants produce a multitude of berries. Birds will eat the fruit (even though they receive little nutritional value from them) and drop the seeds all over the place, perpetuating the spread. The species name of Common Buckthorn, cathartica, refers to how quickly the fruit and seeds go through the system of an animal. This way, the plant has ensured that it is quickly dispersed through the landscape. We call this the “evacuate” propagation method.

Wisconsin gardening comes with many obstacles: rabbits, deer, cold winters, and invasive non-native plant species. In the war against invasive plants,…

What To Do About Buckthorn?

The best time to battle Buckthorn is in late fall/early winter when it is easily recognizable.

This is because Buckthorn holds onto its green leaves much longer than other deciduous trees and shrubs. You’ll also be able to identify it from the bold lenticels that create light-color, horizontal stripes on the dark stems. Larger, mature plants have long thorns on the branches. Scraping the bark reveals a bright orange/yellow color.

November is the perfect time to battle Buckthorn, whether in your yard or natural areas. Plants are moving water and nutrients into their roots for the winter, so herbicide applications are the most effective. Small seedlings and trees can be pulled by hand or using a weed wrench or the like.

Larger plants (1/2″ caliper or more) that are too difficult to pull or too large to be sprayed, can be destroyed with the “cut and paint” method. This is easiest with two people doing the work: one person cuts the woody plants to the ground, and the other will come behind with a container containing the herbicide. Look for pesticides labeled for woody plants like Bonide Stump Out or glyphosate concentrates (like Roundup) mixed with a little water.

Be aware that some herbicides require a minimum temperature to be effective — check the labels. Use a sponge brush to apply the herbicide to the freshly cut stump. We like to add a little red food coloring to the mix so it’s easy to tell which stumps have already been painted. Make sure to thoroughly coat the outer cambium ring (don’t worry about the center on larger stumps). The sponge brush will give you more control so you don’t accidentally drip onto desirable plants.

Burning the debris of branches you’ve cut down is the best way to destroy the seeds so they aren’t spread to another area. If the task of removing large stands of Buckthorn is too daunting, contact a local landscaping company.

Plant Natives After Buckthorn Is Removed

When the Buckthorn is removed, you can begin replacing them with native plants. Re-establishing native plant cover will outcompete Buckthorn for light availability, which will help prevent reinvasion. Researchers at the University of Minnesota have seen that using native plants cuts the amount of returning Buckthorn in half over a few years. Scientists have also seen a 90% reduction in Buckthorn reinvasion when native trees and shrubs are planted. Read more about Controlling Buckthorn (University of Minnesota).

Monitoring The Area For Re-growth

After removing Buckthorn and planting natives, yearly monitoring of the area for re-growth, and promptly removing shoots, will be important to keep this thug out. Making note of which plants did well can help you plan for future restoration efforts in your yard.

Buckthorn Replacement Plant Recommendations

There are many native grasses, groundcovers, perennials, shrubs, canopy, and understory trees that are excellent replacements for Buckthorn. It’s by no means a complete list, but a good sampling of options for a variety of conditions. Once you’ve won the battle, it’ll be easier to spread the word about Buckthorn eradication to your neighbors, and we can finally win the war!

Canopy Trees to Replace Buckthorn

Oaks

Quercus spp.

**NATIVE** Wisconsin native oaks are large and long-lived and considered a keystone species, with significant ecological value. A true canopy tree, while many oaks share similar qualities, they range in height and width, as do the conditions they require in which to thrive. Planting any Oak will reign supreme!

Mature Height: Varies
Mature Spread: Varies
Exposure: Full Sun to Part Shade
Catalog: Varies

Yellow Birch

Betula alleghaniensis

**NATIVE** A long-lived Wisconsin native not planted nearly enough! Yellow Birch is adaptable to most conditions except for compacted and clay soil. Yellow-bronze exfoliating bark, a wintergreen scent, and a brilliant fall color make this an easy choice.

Mature Height: 40-60 feet
Mature Spread: 40-50 feet
Exposure: Full Sun to Part Shade
Catalog: #5, #10, #20 Single Stem and #5, #10 Multi-stem Container Trees

Sugar Maple

Acer saccharum

**NATIVE** The Wisconsin state tree, Sugar Maple is a statement canopy tree most known for its large leaves that turn shades of gold to orange to scarlet in fall, as well as its sap that makes a delicious syrup. In addition to being a great option for areas cleared of Buckthorn!

Mature Height: 50-75 feet
Mature Spread: 45-50 feet
Exposure: Full Sun
Catalog: #5, #10, Container Trees; 1.5” to 4.5” caliper B&B

Quaking Aspen

Populus tremuloides

**NATIVE** Quaking Aspen grows quickly, colonizing open spaces where Buckthorn once stood. Tolerant of many conditions (except drought and shade), its lustrous dark green foliage turns golden in the fall shimmering in the slightest breeze. Tremendously valuable to wildlife.

Mature Height: 40-50 feet
Mature Spread: 20-30 feet
Exposure: Full Sun
Catalog: #5 and #25 single and multi-stem container trees

Shagbark Hickory

Carya ovata

**NATIVE** Shagbark Hickory is a large stature tree with dark green leaves, exfoliating, shaggy bark, and medium-sized nuts. Large leaves help block out the sun from the ground below, helping to keep Buckthorn from re-establishing. Shagbark Hickory has tremendous value to wildlife, insects, and songbirds.

Mature Height: 80 feet
Mature Spread: 40 feet
Exposure: Full Sun to Part Shade
Catalog: #5 and #25 Containers, 1.5” to 4.5” B&B

American Beech

Fagus grandifolia

**NATIVE** An impressive native Wisconsin tree with light gray, smooth bark, and leaves that turn golden-bronze in fall. Its large canopy casts a good amount of shade, helping to keep Buckthorn at bay. Nuts feed a plethora of wildlife and songbirds. It is also a host plant for a staggering number of Lepidoptera larvae.

Mature Height: 60-75 feet
Mature Spread: 55-65 feet
Exposure: Full Sun to Part Shade
Catalog: #5 and #20 Containers, 1.5” B&B

Understory Trees to Replace Buckthorn

Ironwood

Ostrya virginiana

**NATIVE** A small, slow-growing pyramidal tree native to the dry understory in Wisconsin woods. In fall, delicate hop-like seeds decorate the tree, providing interest throughout the seasons. Grows in full sun to full shade and tolerant of many soils – an easy choice to replace Buckthorn.

Mature Height: 25 feet
Mature Spread: 15 feet
Exposure: Full Sun to Full Shade
Catalog: #5 Container, 1.5”, 1.75”, 2” B&B Trees, 6’, 7’, 8’, 9’, 12’, 16’ Shrub Form Trees

Pagoda Dogwood

Cornus alternifolia

**NATIVE** A small tree or large shrub, Pagoda Dogwood has pretty white flowers in spring followed by blue-black berries in summer. Fall foliage color ranges from maroon to purple! Black walnut and deer resistant, it’s a delightful native understory tree to replace Buckthorn.

Mature Height: 15-25 feet
Mature Spread: 15-25 feet
Exposure: Full Sun to Full Shade
Catalog: #2, #10 Container Trees, #25 Multi-Stem Container Tree

Speckled Alder

Alnus incana var rugosa

**NATIVE** Growing as a small tree or multi-stemmed shrub and a tendency to sucker and spread, it provides erosion control along stream banks, ponds, and bogs, while also fixing nitrogen and replenishing soil. Tremendous ecological value for wildlife, songbirds, and pollinators!

Mature Height: 15-25 feet
Mature Spread: 6-15 feet
Exposure: Full Sun to Part Shade
Catalog: #2, #5 Container Trees, #20, #25 Multi-Stem Container Tree

Downy Serviceberry

Amelanchier arborea

**NATIVE** One of several native serviceberries, Downy Serviceberry provides four-season interest beginning in spring with fragrant white flowers followed by edible, red to dark purple berries in June. It’s a versatile understory tree suckering and filling in areas post-Buckthorn. Wildlife loves it.

Mature Height: 15-25 feet
Mature Spread: 10-15 feet
Exposure: Full Sun to Part Shade
Catalog: #5 Container Shrub Form Trees, 6’ Shrub Form Tree B&B

Musclewood

Carpinus caroliniana

**NATIVE** A small Wisconsin native tree that is a favorite for its hardiness, site versatility, and the many benefits that wildlife reaps from its flowers, seeds, and woody stems. An excellent understory tree with a dense canopy, it fills in areas well and provides a beautiful fall color with orange to red leaves.

Mature Height: 25-30 feet
Mature Spread: 25-30 feet
Exposure: Full Sun to Full Shade
Catalog: #5 Containers

Bog Birch

Betula pumila

**NATIVE** Bog Birch thrives in wet areas such as swamps, wetlands, and low-lying areas where flooding is frequent. It’s a good option to replace Buckthorn in moist areas, as it spreads and forms a thicket over time thanks to a shallow root system capable of layering and sending up new shoots. Many wildlife are supported by Bog Birch.

Mature Height: 6-9 feet
Mature Spread: 8 feet
Exposure: Full Sun to Part Shade
Catalog: #5 Containers

Shrubs to Replace Buckthorn

American Filbert

Corylus americana

**NATIVE** Also known as American Hazelnut, this is a versatile understory shrub growing in dry, moist, clay, and sandy soils. A suckering shrub, Filbert will spread over time, filling in areas once occupied by Buckthorn. Beautiful fall color and edible nuts are bonus attributes! Pollinator, bird- and wildlife-friendly!

Mature Height: 8-10 feet
Mature Spread: 8-10 feet
Exposure: Full Sun to Part Shade
Catalog: #2 and #3 Containers, 36”, 48”, and 5’ B&B

Bladdernut

Staphylea trifolia

**NATIVE** An underused native shrub, Bladdernut is a superb replacement for Buckthorn as it handles full sun to full shade, grows vigorously, and is thicket-forming. Clusters of white drooping, bell-shaped flowers are followed by interesting, puffy bladder-like seed capsules that last into winter. Wonderful for wildlife, beneficial insects, and birds!

Mature Height: 10-15 feet
Mature Spread: 8-12 feet
Exposure: Full Sun to Full Shade
Catalog: #2 Containers, 36”, 48”, and 5’ B&B

Buttonbush

Cephalanthus occidentalis

**NATIVE** Buttonbush is a distinctive shrub with unusual-looking, fragrant, spherical flowers that resemble pincushions. Enjoying moist to wet conditions, it is an excellent candidate for filling in areas where Buckthorn once stood, particularly along pond edges, streams, wetlands, and floodplains.

Mature Height: 6-8 feet
Mature Spread: 6-8 feet
Exposure: Full Sun to Full Shade
Catalog: #2 Containers

Silky Dogwood

Cornus amomum

**NATIVE** A versatile, medium-to-large-sized shrub adaptable to many sites. Pretty white flowers bloom in spring, followed by blue fruit that ripens in late summer. Effective in fighting invasive species as it tends to colonize. The fruit is highly prized by wildlife, insects, and songbirds.

Mature Height: 8-10 feet
Mature Spread: 8 feet
Exposure: Full Sun to Part Shade
Catalog: #2, #5 Containers

Gray Dogwood

Cornus racemosa

**NATIVE** Gray Dogwood is slightly larger than Silky and is best used in drier locations. With vigorous growth and a tendency to colonize, it is particularly useful in combatting Buckthorn. White spring flowers are followed by white fruit that wildlife and songbirds relish. Pollinator plant.

Mature Height: 8-12 feet
Mature Spread: 8-12 feet
Exposure: Full Sun to Part Shade
Catalog: #3 Containers

American Elderberry

Sambucus canadensis

**NATIVE** A large, sprawling, and beautiful native shrub, American Elderberry has bright green leaves and clusters of white fragrant flowers in early summer. Suckering and forming colonies, it’s a great option to replace Buckthorn in low, moist spots. The juicy black fruits are edible!

Mature Height: 6-12 feet
Mature Spread: 6-12 feet
Exposure: Full Sun to Part Shade
Catalog: #2 and #5 Containers

Conifers to Replace Buckthorn

Eastern White Pine

Pinus strobus

**NATIVE** A pyramid of soft, rich green to bluish-green foliage that with age, opens and features strong horizontal branching. Begins producing cones between 5 to 10 years old, the seeds of which provide food for bears, rabbits, squirrels, and at least 16 species of birds.

Mature Height: 50-80 feet
Mature Spread: 20-40 feet
Exposure: Full Sun
Catalog: #5 Container, 5’ to 9’ B&B

Northern White Cedar

Thuja occidentalis

**NATIVE** A medium-sized native Wisconsin conifer that thrives in moist, rich soil – a fantastic tree to use in wetter areas where Buckthorn has been eliminated. An excellent tree for wildlife and birds, providing cover from winter weather with its dense foliage.

Mature Height: 20-30 feet
Mature Spread: 10-15 feet
Exposure: Full Sun to Part Shade
Catalog: #5 Container

Oldfield Common Juniper

Juniperus communis var. depressa

**NATIVE** A rough and tough Wisconsin native evergreen that makes a superior groundcover with dense green needles. Planting post-Buckthorn will fill in areas and help prevent re-establishment. Blue seed cones are prized by birds – a critical food source in the winter.

Mature Height: Less than 4 feet
Mature Spread: 10 feet
Exposure: Full Sun
Catalog: #2 Containers

Eastern Red Cedar

Juniperus virginiana

**NATIVE** Commonly found in rocky, dry soil, A hardy evergreen native to Wisconsin. Notable for its pretty, reddish, exfoliating bark and evergreen leaves that develop a brownish/purple hue in winter. Dense foliage makes an excellent windbreak or screen after Buckthorn has been removed leaving empty spaces.

Mature Height: 30- 40 feet
Mature Spread: 8-20 feet
Exposure: Full Sun
Catalog: #5 Containers, 5’, 6’, 7’ B&B

Tamarack

Larix laricina

**NATIVE** As a deciduous conifer, this Wisconsin native tree turns a beautiful yellow color in autumn, and then loses its needles for winter. Tamarack thrives in moist to wet areas and is a good choice along streambanks, ponds, lakes, or low-lying areas. Birds use Tamarack for food and shelter and is a host plant for many moths.

Mature Height: 30-50 feet
Mature Spread: 10-15 feet
Exposure: Full Sun
Catalog: #5 and #10 Containers

Canadian Hemlock

Tsuga canadensis

**NATIVE** A beautiful choice to replace Buckthorn in shady areas. Light yellow-green spring foliage turns a deep green and is decorated with petite, lantern-shaped cones. Cool and moist sites with good drainage are a must for this native conifer. A valuable source of food and habitat to wildlife. Also a host plant to several moth species.

Mature Height: 25-45 feet
Mature Spread: 15-25 feet
Exposure: Full Sun to Full Shade
Catalog: #5 and #15 Containers, 5’, 6’, 7’ B&B

Perennials to Replace Buckthorn

Butterflyweed

Asclepias tuberosa

**NATIVE** Flowers are of high value to native pollinators and hummingbirds, particularly to Monarch butterflies as it is a larval host plant. A versatile plant, it is tolerant of many conditions and will reseed and spread over time, filling in areas once occupied by Buckthorn.

Mature Height: 24-36 inches
Mature Spread: 9-18 inches
Exposure: Full Sun to Part Shade
Catalog: #1 Containers

Pale Purple Coneflower

Echinacea pallida

**NATIVE** Pale purple petals droop downward setting it apart from other coneflowers. A deep taproot, characteristic of many prairie plants, makes it drought tolerant. Reseeds easily, spreading and filling in bare spots. Pollinator and bird-friendly!

Mature Height: 2-3 feet
Mature Spread: 12-18 inches
Exposure: Full Sun
Catalog: #1 Containers

Wild Geranium

Geranium maculatum

**NATIVE** Clusters of saucer-shaped purple-pink flowers. Adaptable to various soils and light, but performs best with some shade to keep the roots cool. Spreads via shallow rhizomes and self-seeding, taking hold after the removal of Buckthorn and Garlic Mustard.

Mature Height: 12-24 inches
Mature Spread: 18-24 inches
Exposure: Part Shade
Catalog: #1 Containers

Red Milkweed

Asclepias incarnata

**NATIVE** Red Milkweed is a fast-growing, wet soil-loving, Wisconsin native perennial with fragrant deep pink flowers that attract many insects and Monarchs. A fast growth rate and plentiful reseeding make this a great option to replace Buckthorn in more moist areas.

Mature Height: 36-60 inches
Mature Spread: 36 inches
Exposure: Full Sun to Part Shade
Catalog: #2 Containers

Zig Zag Goldenrod

Solidago flexicaulis

**NATIVE** A boon for wildlife later in the season! Prefers part-shade and fertile soil but is tolerant of heavy shade and clay soil, and once established, dry soil. With its adaptability to various conditions and easy-spreading nature, it is a great option after Buckthorn is removed.

Mature Height: 12-36 inches
Mature Spread: 24 inches
Exposure: Full Sun to Full Shade
Catalog: #1 Containers

Bigleaf Aster

Eurybia macrophylla

**NATIVE** A woodland perennial, it spreads by rhizomes to form a lush carpet of large, hairy leaves topped with delicate thin lavender/blue flowers. It’s an excellent replacement for Buckthorn especially on hillsides and slopes as it helps to stabilize the soil.

Mature Height: 12-26 inches
Mature Spread: 24 inches
Exposure: Full Sun to Part Shade
Catalog: #1 Containers

Grasses to Replace Buckthorn

Prairie Dropseed Grass

Sporobolus heterolepis

**NATIVE** A warm-season, clump-forming native prairie grass that forms tufts of emerald-green foliage with airy, popcorn-scented seed heads. Excellent heat and drought tolerance for tough, difficult sites and great for areas once populated by Buckthorn.

Mature Height: 24 inches
Mature Spread: 18 inches
Exposure: Full Sun
Catalog: #1 Containers

Little Bluestem

Schizachyrium scoparium

**NATIVE** Little Bluestem is a clump-forming, warm-season grass. In fall, the foliage changes to a flaming orange or striking red, topped with fluffy silver seed stalks. Deep roots make it a great soil stabilizer and perfect for hillsides. High ecological value to wildlife.

Mature Height: 24-36 inches
Mature Spread: 12-18 inches
Exposure: Full Sun to Part Shade
Catalog: #1 Containers

Pennsylvania Sedge

Carex pensylvanica

**NATIVE** Commonly found growing in the understory, Pennsylvania Sedge forms a lush, undulating carpet of green. It is a living green mulch covering bare soil, filling in gaps, and suppressing weeds – a superior selection for shadier areas once consumed by Buckthorn.

Mature Height: 6-12 inches
Mature Spread: 12-15 inches
Exposure: Part Shade to Full Shade
Catalog: #1 Containers

Marsh Bluegrass

Poa palustris

**NATIVE** Red Milkweed is a fast-growing, wet soil-loving, Wisconsin native perennial with fragrant deep pink flowers that attract many insects and Monarchs. A fast growth rate and plentiful reseeding make this a great option to replace Buckthorn in more moist areas.

Mature Height: 36-60 inches
Mature Spread: 36 inches
Exposure: Full Sun to Part Shade
Catalog: #2 Containers

Bottlebrush Grass

Elymus hystrix

**NATIVE** A terrific grass that thrives in dry to sandy and moist to loamy conditions, making it incredibly versatile. It tolerates black walnut toxicity, drought, clay, and poor soils. Easily spreading over time, it will repopulate the soil where an area has been cleared of Buckthorn.

Mature Height: 36-48 inches
Mature Spread: 12-24 inches
Exposure: Part Shade to Full Shade
Catalog: #1 Containers

Muskingum (Palm) Sedge

Carex muskingumensis

**NATIVE** A clump-forming, medium-sized sedge to replace Buckthorn in wetland and swampy areas! Spreading by rhizomes and seed, it forms colonies of pretty green, feathery, palm-like foliage with light green to brown spikelets rising above the foliage.

Mature Height: 12-36 inches
Mature Spread: 12-48 inches
Exposure: Full Sun to Part Shade
Catalog: #1 Containers