Invasive Shade-Tolerant Garden Plants in Wisconsin

Wisconsin's diverse landscapes, including its dense forests, wetlands, and shaded gardens, are vulnerable to invasive plant species that thrive in low-light environments. These invasive plants can spread quickly, outcompeting native species and disrupting local ecosystems. Understanding these plants and choosing native alternatives is essential for preserving Wisconsin’s natural beauty and biodiversity.

Reed Canary Grass (Phalaris arundinacea)

List of Invasive Shade-Tolerant Garden Plants in Wisconsin

1. Japanese Barberry (Berberis thunbergii)

• Description: A thorny shrub with bright red berries and small, glossy leaves, often planted for its ornamental appeal.

• Impact: Japanese Barberry forms dense thickets in shaded areas, outcompeting native plants and altering soil chemistry, which can negatively affect the surrounding ecosystem.

• Garden Alternative: Winterberry (Ilex verticillata) - A native shrub with vibrant red berries that supports local wildlife and thrives in shaded areas.

2. Garlic Mustard (Alliaria petiolata)

• Description: A biennial herb with heart-shaped leaves and small white flowers that emit a garlic-like odor when crushed.

• Impact: Garlic Mustard spreads rapidly in shaded woodlands, outcompeting native plants and reducing biodiversity.

• Garden Alternative: Wild Ginger (Asarum canadense) - A native ground cover with heart-shaped leaves that thrives in shaded environments and offers similar coverage without being invasive.

3. Common Buckthorn (Rhamnus cathartic)

• Description: A deciduous shrub or small tree with dark green leaves and small black berries. Initially introduced as a hedge plant, it has since become invasive.

• Impact: Common Buckthorn invades woodlands and shaded areas, forming dense thickets that prevent native plants from growing.

• Garden Alternative: American Hazelnut (Corylus americana) - A native shrub that provides valuable habitat and food for wildlife, thriving in shaded environments.

4. Japanese Knotweed (Fallopia japonica)

• Description: A robust perennial with large, heart-shaped leaves and clusters of small white flowers. It spreads aggressively, particularly in riparian areas.

• Impact: Japanese Knotweed forms dense stands that outcompete native vegetation, reducing biodiversity and altering habitat conditions in shaded areas.

• Garden Alternative: Joe-Pye Weed (Eutrochium purpureum) - A native perennial that supports pollinators and thrives in similar conditions without becoming invasive.

5. Reed Canary Grass (Phalaris arundinacea)

• Description: A tall, perennial grass with broad green leaves, often found in wet, shaded areas.

• Impact: Reed Canary Grass spreads aggressively, forming dense stands that outcompete native vegetation, particularly in wetland habitats.

• Garden Alternative: Prairie Cordgrass (Spartina pectinata) - A native grass that provides similar height and structure in wet areas without the invasive spread.

6. English Ivy (Hedera helix)

• Description: An evergreen vine with dark green, lobed leaves, commonly used as ground cover or for climbing structures.

• Impact: English Ivy spreads aggressively, smothering native plants and trees, reducing biodiversity, and damaging ecosystems in shaded environments.

• Garden Alternative: Virginia Creeper (Parthenocissus quinquefolia) - A native vine that provides similar coverage with vibrant fall color, supporting local wildlife without overwhelming native plants.

7. Multiflora Rose (Rosa multiflora)

• Description: A thorny shrub with clusters of small white flowers and bright red rose hips, often used as a living fence.

• Impact: Multiflora Rose forms dense thickets in shaded areas, outcompeting native plants and reducing habitat quality for wildlife.

• Garden Alternative: Pasture Rose (Rosa carolina) - A native rose with fragrant pink flowers that supports pollinators and thrives in similar conditions.

8. Lesser Celandine (Ficaria verna)

• Description: A low-growing perennial with shiny, heart-shaped leaves and bright yellow flowers, often found in moist, shaded areas.

• Impact: Lesser Celandine forms dense mats that outcompete native spring ephemerals, reducing biodiversity in shaded, moist environments.

• Garden Alternative: Bloodroot (Sanguinaria canadensis) - A native perennial with white flowers that supports early-season pollinators and thrives in similar conditions.

9. Japanese Honeysuckle (Lonicera japonica)

• Description: A vigorous vine with fragrant white to yellow flowers and dark green leaves, often planted for its ornamental purposes.

• Impact: Japanese Honeysuckle forms dense mats that smother native plants, reducing biodiversity in shaded and woodland areas.

• Garden Alternative: Trumpet Honeysuckle (Lonicera sempervirens) - A native vine with tubular red flowers that attract hummingbirds and thrive in shaded environments.

Conclusion

Invasive shade-tolerant plants can significantly impact Wisconsin’s ecosystems by outcompeting native species and altering local habitats. By selecting native, non-invasive alternatives, gardeners can help maintain ecological balance, support local wildlife, and preserve the natural beauty of Wisconsin’s landscapes.

For more information and to connect with other gardening enthusiasts, join our Facebook group: Shade Gardening.