Invasive Shade-Tolerant Garden Plants in Iowa

Iowa’s natural landscapes, including its woodlands and shaded areas, are vulnerable to invasive plants that thrive in low-light conditions. These invasive species can spread quickly, outcompeting native plants and disrupting local ecosystems. Identifying these invasive plants and choosing native alternatives is essential for preserving Iowa’s ecological balance and maintaining the beauty of its natural habitats.

Reed Canary Grass (Phalaris arundinacea)

List of Invasive Shade-Tolerant Garden Plants in Iowa

1. Garlic Mustard (Alliaria petiolata)

• Description: Garlic Mustard is a biennial herb with heart-shaped leaves and small white flowers. It releases a garlic-like odor when crushed.

• Impact: This plant outcompetes native vegetation in shaded woodlands, reducing biodiversity and altering habitat structure.

• Garden Alternative: Wild Ginger (Asarum canadense) - A native ground cover with heart-shaped leaves that thrives in shade and supports local ecosystems without being invasive.

2. Japanese Barberry (Berberis thunbergii)

• Description: Japanese Barberry is a small, thorny shrub with bright red berries and small, glossy leaves. It is often used for ornamental purposes.

• Impact: It forms dense thickets in shaded areas, which can crowd out native plants and alter soil chemistry, negatively affecting the surrounding ecosystem.

• Garden Alternative: Ninebark (Physocarpus opulifolius) - A native shrub that provides beautiful flowers and foliage, supports local wildlife, and thrives in shaded conditions.

3. Creeping Bellflower (Campanula rapunculoides)

• Description: Creeping Bellflower is a perennial with tall spikes of purple, bell-shaped flowers. It spreads through rhizomes and seeds.

• Impact: This plant spreads aggressively in shaded areas, outcompeting native plants and reducing plant diversity.

• Garden Alternative: Bluebells (Mertensia virginica) - A native perennial with similar blue flowers, supporting early-season pollinators and thriving in shaded woodlands.

4. Norway Maple (Acer platanoides)

• Description: Norway Maple is a large, deciduous tree with broad, dark green leaves. It is often planted for its dense shade.

• Impact: It produces dense shade that suppresses native undergrowth, reducing biodiversity in forested and shaded areas.

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

5. Reed Canary Grass (Phalaris arundinacea)

• Description: Reed Canary Grass is a tall, perennial grass with broad leaves and dense seed heads. It’s commonly found in moist, shaded areas.

• Impact: It spreads aggressively, forming dense stands that outcompete native vegetation, particularly in wet, shaded habitats.

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

6. Common Buckthorn (Rhamnus cathartic)

• Description: Common Buckthorn is a deciduous shrub or small tree with dark green leaves and small black berries. It was originally planted as a hedge.

• Impact: It 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.

Conclusion

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

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