Invasive Species

Weed Out Invasives

Ecological Invaders of the Milwaukee County Parks

Invasive Weeds crowd out native vegetation, destroy wildlife habitats and eliminate ecological diversity. Some of the most threatening to our Milwaukee Parks are shown below. Click on the picture to learn more and surf to our schedule to sign up to help!

Buckthorn - Rhamnus cathartica L, Rhamnus frangula

Dame's Rocket - Hesperis matronalis L

Even though dame's rocket is a close relative of garlic mustard, it is included in many "wildflower" seed mixes, so read the label carefully to avoid adding this aggressive weed to your landscape. Dame's rocket is a short-lived perennial with 4-petaled white, pink, or purple flowers that bloom prolifically from May into July. The leaves are lance-shaped and serrated. (The similar appearing native wildflower, garden phlox (Phlox paniculata) has 5 petals to its flowers and the leaf edges are smooth.) Dame's rocket has a basal rosette of lance-shaped leaves that remain green through winter.

Garlic Mustard: A Prolific Invasive - Alliaria petiolata

Garlic Mustard : First Year Growth
Garlic mustard is a moderately tall (up to three feet) biennial herb with small white flowers. In the first year, the plant grows as a vegetative rosette close to the ground and has broad, kidney-shaped, round-toothed leaves. Early in the growing season of the second year, the plants produce an erect flowering stem with numerous quarter-inch-wide four-petal flowers clustered at the top. Leaves on the erect stem are alternate and more triangular and serrated than those of the basal rosette. Each flower may produce an oblong capsule called a silique that may be up to four inches long. An individual plant can produce thousands of seeds. By midsummer the leaves have mostly died back and only the drying stems with many papery capsules remain. Crushed stems and leaves of garlic mustard give off a distinct odor of garlic.


Garlic Mustard : Second Year Growth
Healthy Forest Floor: This beautiful woodland floor has a great variety of wildflowers like trillium, mayapple and Solomon’s plume. Young shrubs and trees are also present - ready to replace the older stock when they die.

Forest Floor Overrun by Garlic Mustard

By mid-summer of its second year Garlic Mustard dies off and leaves unsightly stalks (note the rosettes of first year growth in the foreground)

Honeysuckle - Lonicera japonica, Lonicera maackii