Invasive Shade-Tolerant Garden Plants in Delaware

Delaware’s diverse ecosystems, including its woodlands and wetlands, face challenges from several garden plants that thrive in shaded conditions and have become invasive. These plants, often chosen for their ornamental appeal or ease of maintenance, can escape gardens and spread into natural areas, outcompeting native species and disrupting local ecosystems. By understanding these invasive plants and opting for native alternatives, gardeners can help preserve Delaware’s natural beauty and ecological balance.

Tree of Heaven (Ailanthus altissima)

List of Invasive Shade-Tolerant Garden Plants in Delaware

1. Japanese Knotweed (Fallopia japonica)

• Description: Japanese Knotweed is a vigorous, perennial herb with large, heart-shaped leaves and tall, bamboo-like stems. It’s commonly used for ground cover due to its fast growth.

• Impact: Forms dense thickets that can overwhelm native vegetation and disrupt shaded woodland and riparian areas.

• Garden Alternative: Wild Ginger (Asarum canadense) - A native ground cover with attractive heart-shaped leaves that thrives in shade without spreading aggressively.

2. English Ivy (Hedera helix)

• Description: English Ivy is a climbing vine with dark green, lobed leaves. It’s used as ground cover or for covering walls and fences in shaded garden areas.

• Impact: Spreads aggressively, smothering native plants and trees, leading to significant ecological damage in shaded environments.

• Garden Alternative: Creeping Juniper (Juniperus horizontalis) - A native ground cover with evergreen foliage that provides year-round interest without invasive tendencies.

3. Burning Bush (Euonymus alatus)

• Description: Burning Bush is a deciduous shrub known for its bright red fall foliage and dense growth. It’s frequently used as a hedge or ornamental plant.

• Impact: Spreads rapidly, forming dense thickets that outcompete native plants and alter local habitats.

• Garden Alternative: Red Chokeberry (Aronia arbutifolia) - A native shrub with white flowers and red berries that supports wildlife and provides vibrant fall color.

4. Japanese Barberry (Berberis thunbergii)

• Description: Japanese Barberry is a thorny shrub with bright red or orange leaves and small berries. It’s often planted for its ornamental value and ease of care.

• Impact: Spreads aggressively, forming dense stands that displace native plants and affect forest health.

• Garden Alternative: Sweetspire (Itea virginica) - A native shrub with fragrant white flowers and attractive foliage that thrives in shade and supports local wildlife.

5. Tree of Heaven (Ailanthus altissima)

• Description: Tree of Heaven is a fast-growing tree with large, pinnate leaves and a broad canopy. It’s used for quick shade and its resilience in urban settings.

• Impact: Spreads rapidly, forming dense stands that outcompete native trees and alter soil conditions, impacting local ecosystems.

• Garden Alternative: American Hornbeam (Carpinus caroliniana) - A native tree with attractive, smooth bark and resilient foliage that provides shade without being invasive.

6. Garlic Mustard (Alliaria petiolata)

• Description: Garlic Mustard is a biennial herb with heart-shaped leaves and small white flowers. It’s commonly used as a ground cover in shaded garden beds.

• Impact: Spreads aggressively, outcompeting native plants and disrupting shaded woodland areas.

• Garden Alternative: Goldenseal (Hydrastis canadensis) - A native herb with medicinal properties that thrives in shaded conditions and supports local ecosystems.

7. Japanese Honeysuckle (Lonicera japonica)

• Description: Japanese Honeysuckle is a vigorous, semi-evergreen vine with fragrant white to yellow flowers and dark green leaves. It is often used for its attractive blooms and rapid growth.

• Impact: Spreads quickly, forming dense mats that smother native plants and reduce biodiversity in shaded environments.

• Garden Alternative: American Clematis (Clematis virginiana) - A native vine with white flowers that supports pollinators and grows well in shaded areas.

8. Amur Honeysuckle (Lonicera maackii)

• Description: Amur Honeysuckle is a deciduous shrub with fragrant white to yellow flowers and red berries. It is commonly planted for its ornamental value and fast growth.

• Impact: Spreads rapidly and forms dense thickets, displacing native vegetation and altering forest dynamics.

• Garden Alternative: Winterberry Holly (Ilex verticillata) - A native shrub with bright red berries that provide winter interest and support local wildlife.

9. Privet (Ligustrum spp.)

• Description: Various Privet species are used as hedges and for ground cover, known for their dense foliage and small white flowers.

• Impact: Invades natural areas, forming dense thickets that displace native vegetation and reduce habitat quality.

• Garden Alternative: Ninebark (Physocarpus opulifolius) - A native shrub with attractive bark and flowers that supports wildlife and maintains ecological balance.

10. Siberian Elm (Ulmus pumila)

• Description: Siberian Elm is a fast-growing tree with small serrated leaves and a broad canopy, often planted for quick shade.

• Impact: Spreads rapidly and can form dense stands that outcompete native trees and disrupt local ecosystems.

• Garden Alternative: Eastern Red Cedar (Juniperus virginiana) - A native evergreen tree that provides excellent shade and habitat for wildlife.

11. Korean Pine (Pinus koraiensis)

• Description: Korean Pine is an ornamental evergreen tree with long needles and cones, used for its attractive foliage.

• Impact: Can spread into natural areas and outcompete native vegetation, particularly in shaded environments.

• Garden Alternative: Pitch Pine (Pinus rigida) - A native pine tree that supports local ecosystems and provides habitat without becoming invasive.

Conclusion

While these invasive plants are commonly used in shaded gardens across Delaware, their tendency to spread and outcompete native species can lead to significant ecological harm. By opting for native, non-invasive alternatives, gardeners can contribute to the preservation of Delaware’s natural landscapes, support local wildlife, and maintain the state’s environmental health.

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