How to identify and eradicate weeds in especially rainy season

“I am struggling to keep up with the weeds in my garden. Is there a difference between a weed and a garden plant?”

— Benjamin Warren, Elk Grove Village

The staff at the Chicago Botanic Garden is also dealing with a robust weed population this spring. As soon as they are pulled, more weeds seem to appear. Lots of rainy weather has meant little time to deal with weeds while it also promoted heavy weed growth.

I define a weed as a plant that is growing where it is not wanted in the garden. Different gardeners have different ideas of what constitutes a weed. For example, violets in the lawn are considered weeds by some gardeners and nice seasonal color accents by others. Dandelions are widely recognized as weeds; however, their peak flowering time in early spring is when many bees and other pollinators emerge and use dandelion flowers as a food source.

There is a biological difference between a weedy plant and an invasive plant. Weedy plants readily spread, especially in disturbed areas, but generally do not pose a threat to the integrity of native plant communities. Invasive plants are usually non-native and can establish themselves within existing native plant communities.

Invasive plants pose a threat to the integrity of the plant community. When invasive plants are introduced to a new location, either intentionally or accidentally, they can spread prolifically, out-compete native species for resources, and eventually even dominate the landscape. Buckthorn is an example of an invasive plant in the Chicago region that requires continual management for native communities to thrive. Buckthorn is also a common weed in home gardens, and I regularly pull it out of my garden.

Some factors common to many invasive plants include rapid growth and early maturity, production of many seeds, wide dispersal of seeds by birds and wind, seeds that germinate quickly, few natural enemies and an ability to reproduce vegetatively. Use regional resources for guidance regarding invasive plants. The Chicago Botanic Garden has an invasive plant policy that can be accessed at chicagobotanic.org. The policy can provide guidance to help you avoid choosing an invasive plant for your garden. You can run across plants for sale that are considered invasive in native plant communities.

Goutweed (Aegopodium podagraria) is a fearsome invader in many home gardens, and it makes me cringe when I see it. You can dig it out multiple times and it will reappear and will grow within clumps of perennials and spread to other areas when dividing and transplanting. I have sprayed patches of it in my garden with an herbicide four times last year and it is still coming back.

This weed takes sustained management over a long period of time to control.

Star of Bethlehem (Ornithogalum umbellatum) is another plant pest common in home gardens. The best control is to carefully dig it out, making sure you remove the bulbs underground or it will continue to grow back. The Star of Bethlehem in my garden is starting to show white flowers now. This plant has moved into my lawn too. The plant will go dormant and disappear in summer.

Garlic mustard (Alliaria petiolata) is another invasive weed that is flowering now. Its leaves are rounder and form in rosettes at ground level during its first year of growth. The leaves send up a flowering stem and become more triangular and heart-shaped with toothed edges. The small white flowers have four petals.

Remove flowering plants and secure in plastic trash bags to prevent any seeds from spreading. Prioritize your time to pull out flowering garlic mustard to save work in the future.

Watch for buckthorn, mulberry and boxelder tree seedlings in your borders as they are easy to pull out when they are seedlings. One of the best times to weed is when the ground is moist to get more of the roots out.

For more plant advice, contact the Plant Information Service at the Chicago Botanic Garden at plantinfo@chicagobotanic.org. Tim Johnson is senior director of horticulture at the Chicago Botanic Garden.