The Top 10 Invasive Species Threatening Your Landscape

Invasive species are more than just a nuisance - they threaten the beauty, biodiversity, and long-term health of your property. From aggressive woody shrubs to persistent weeds, these nonnative plants outcompete native vegetation, degrade soil quality, and make your landscape harder to maintain.

The sooner you can spot them and manage them effectively, the better your lawn, garden, and natural areas will thrive. Here's a look at the ten most common invasive species we see in southeastern Wisconsin, how they impact your landscape, and how to identify them.

1). Common Buckthorn

Buckthorn is widely considered one of the most destructive invasive plants in Wisconsin. It spreads rapidly, leafs out earlier than native species, and forms dense thickets that prevent native plants and tree seedling from growing.

Effects on your landscape:

• Crowds out native trees and shrubs

• Alters soil chemistry, making it harder for native plants to reestablish

• Acts as a host for pests and diseases

• Creates poor wildlife habitat

How to identify it:

• Dark green, glossy leaves that stay on late into fall

• Small thorns at the end of branches

• Black berries in late summer and fall

2). Bush Honeysuckles (Amur, Tartarian, Morrow's)

Bush honeysuckles were once planted as ornamentals and wildlife shrubs, but they now aggressively invade woodlands and residential landscapes.

Effects on your landscape:

• Forms dense understory thickets

• Shades out native wildflowers and young trees

• Reduces biodiversity and wildlife habitat

• Spreads rapidly through bird-dispersed berries

How to identify them:

• Early leaf-out in spring before native shrubs

• Hollow stems

• Red or orange berries in fall

3). Japanese Barberry

Japanese Barberry is a compacted but aggressive shrub that thrives in shaded areas and spreads quickly once establishes.

Effects on your landscape:

• Crowds out native understory plants

• Creates dense, thorny growth that's difficult to remove

• Alters soil conditions

• Increases favorable habitat for ticks

How to identify:

• Small oval leaves, often reddish or purple

• Sharp spines along branches

• Bright red berries persisting into winter

4). Multiflora Rose

This fast-growing, thorny shrub forms nearly impenetrable thickets that can quickly overtake open land and field edges.

Effects on your landscape:

• Displaces native grasses and shrubs

• Makes mowing and maintenance difficult

• Reduces access to natural areas

• Spreads rapidly via seeds and arching canes

How to identify:

• Long arching stems covered in thorns

• Clusters of small white flowers in late spring

• Dense, tangled growth patters

5). Round-Leaf Bittersweet

Round-leaf bittersweet is often confused with native bittersweet but is far more aggressive and damaging.

Effects on your landscape:

• Climbs and strangles trees and shrubs

• Blocks sunlight for reaching host plants

• Can cause structural damage to trees

• Spreads rapidly through birds and root systems

How to identify it:

• Round, glossy leaves

• Twining vines wrapping tightly around other plants

• Orange berries in fall

6). Garlic Mustard

Garlic mustard is one of the most common woodland invasives in Wisconsin and spreads rapidly in shaded areas.

Effects on your landscape:

• Releases chemicals that suppress native plant growth

• Disrupts soil fungi essential to tree health

• Quickly forms dense groundcover

• Prevents native seedlings from establishing

How to identify it:

• Heart-shaped leaves

• Small white flowers in spring

• Garlic odor when leaves are crushed

7). Dame's Rocket

Often mistaken for native phlox, Dame's Rocket is a deceptive invasive that spreads easily in disturbed soils.

Effects on your landscape:

• Outcompetes native wildflowers

• Reduces plant diversity in woodlands and roadsides

• Spreads rapidly by seed

How to identify:

• Purple, pink, or white flowers

• Four petals per flower (native phlox has five)

• Upright growth 2-4 feet tall

8). Japanese Knotweed

Japanese Knotweed is one of the most aggressive invasive plants in North America and extremely difficult to eradicate.

Effects on your landscape:

• Displaces nearly all other vegetation

• Damages pavement, retaining walls, and foundations

• Spreads aggressively through underground rhizomes

• Increases erosion along waterways

How to identify:

• Bamboo-like hollow stems

• Large heart-shaped leaves

• White flower clusters in late summer

9). Common Reed (Phragmites)

Common Reed dominates wetlands and low-lying areas, forming tall, dense stands that crowd out native wetland plants.

Effects on your landscape:

• Eliminates native wetland vegetation

• Reduces wildlife habitat

• Alters water flow and soil conditions

• Spreads quickly through rhizomes

How to identify it:

• Tall stems (often 8-12 feet)

• Large feathery seed heads

• Dense monoculture growth near water

10). Reed Canary Grass

Reed Canary Grass is one of the most persistent invasive grasses in Wisconsin.

Effects on your landscape:

• Forms dense monocultures in wet and low areas

• Suppresses native grasses and sedges

• Reduces habitat diversity

How to identify it:

• Course, light-green blades

• Dense clumping growth

• Found in ditches, wetlands, and moist soils

Why Early Invasive Species Control Matters

Once invasive plants are established, they become harder and more expensive to control, Left unmanaged, they can:

• Permanently alter soil conditions

• Reduce native plant and wildlife populations

• Spread rapidly across property lines

• Increase long-term maintenance costs

How YPGA Can Help

Effective invasive species management requires proper identification, timing, and targeted treatment methods. Your Personal Gardener & Arborist offers professional Invasive Species Control services, including:

• On-site identification and evaluation

• Species-specific removal and treatment plans

• Prevention strategies to reduce reinfestation

• Long-term monitoring and restoration support

Whether you're dealing with a small infestation or widespread invasive growth, YPGA creates customized solutions to restore balance and protect your landscape.

Ready to Take Control of Invasive Species?

Don't let invasive plants take over your property.

Contact YPGA today to schedule an Invasive Species Control Consultation and reclaim your landscape for the long term.

https://www.ypgausa.com/contact