Invasive Shade-Tolerant Garden Plants in New Hampshire

New Hampshire’s picturesque forests and shaded landscapes are threatened by invasive plant species that thrive in low-light environments. These invasive plants can spread rapidly, outcompeting native species and disrupting local ecosystems. Identifying these invasive plants and choosing native alternatives is crucial for preserving New Hampshire’s natural beauty and biodiversity.

Burning Bush (Euonymus alatus)

List of Invasive Shade-Tolerant Garden Plants in New Hampshire

1. Japanese Barberry (Berberis thunbergii)

• Description: A small, 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: Highbush Blueberry (Vaccinium corymbosum) - A native shrub with edible berries that supports local wildlife and thrives in shaded areas.

2. Burning Bush (Euonymus alatus)

• Description: A deciduous shrub known for its bright red foliage in the fall and dense growth habit.

• Impact: Burning Bush spreads aggressively, especially in shaded areas, outcompeting native plants and reducing biodiversity.

• Garden Alternative: Witch Hazel (Hamamelis virginiana) - A native shrub with yellow fall flowers and brilliant autumn foliage that supports local ecosystems.

3. Garlic Mustard (Alliaria petiolata)

• Description: A biennial herb with heart-shaped leaves and small white flowers, emitting 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.

4. Oriental Bittersweet (Celastrus orbiculatus)

• Description: A vigorous vine with bright orange berries and glossy green leaves, often used for decorative purposes.

• Impact: Oriental Bittersweet rapidly covers and smothers native trees and shrubs, leading to significant ecological disruption in shaded environments.

• Garden Alternative: American Bittersweet (Celastrus scandens) - A native vine with similar ornamental value but without the invasive characteristics.

5. 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.

6. Norway Maple (Acer platanoides)

• Description: A large deciduous tree with broad, dark green leaves, often planted for its dense shade and fall color.

• Impact: Norway Maple produces dense shade that suppresses native undergrowth, reducing plant diversity in forested and shaded areas.

• Garden Alternative: Sugar Maple (Acer saccharum) - A native tree that provides similar shade while supporting a diverse understory of native plants.

7. 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.

8. 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.

9. Periwinkle (Vinca minor)

• Description: A low-growing, evergreen ground cover with glossy leaves and blue or purple flowers. It spreads rapidly and is commonly used in shaded gardens.

• Impact: Periwinkle’s aggressive growth can overshadow and outcompete native ground covers, leading to reduced biodiversity in shaded areas.

• Garden Alternative: Bunchberry (Cornus canadensis) - A native ground cover that offers year-round appeal and supports local wildlife in shaded environments.

Conclusion

Invasive shade-tolerant plants can significantly impact New Hampshire’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 New Hampshire’s landscapes.

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