“I’m 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
Chicago Botanic Garden staff are also dealing with a robust weed population this spring. As soon as they are pulled, more weeds seem to appear. Lots of rainy weather meant little time to deal with weeds and at the same time encouraged heavy weed growth.
I define a weed as a plant that grows where it is not wanted in the garden. Different gardeners have different ideas about what constitutes a weed. For example, violets in the lawn are considered weeds by some gardeners and beautiful seasonal color accents by others. Dandelion is widely recognized as a weed; However, their flowering time is in the spring when many bees and other pollinators emerge and use dandelion flowers as a food source.
There is a biological difference between a weed plant and an invasive plant. Weed plants spread easily, particularly 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 introduced to a new site, intentionally or accidentally, invasive plants can proliferate, displacing native species for resources and eventually even dominating the landscape. Sea buckthorn is an example of an invasive plant in the Chicago area that requires continued management for native communities to thrive. Sea buckthorn is also a common weed in home gardens and I regularly pull it from my garden.
Some factors common to many invasive plants include rapid growth and early maturity, high seed production, wide dispersal of seeds by birds and wind, seeds that germinate quickly, few natural predators, and the ability to vegetatively reproduce. Use regional resources for guidance on invasive plants. The Chicago Botanic Garden has an invasive plant policy that can be accessed at chicagobotanic.org. The guideline can help you avoid choosing an invasive plant for your garden. You may come 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 up multiple times and it will reappear and grow in clumps of perennials and spread to other areas as you divide and transplant. I sprayed patches of it with an herbicide in my garden four times last year and it’s still coming back.
This weed needs sustained treatment over a long period of time to control it.
Star of Bethlehem (Ornithogalum umbellatum) is another common pest in home gardens. The best control is to dig it up carefully and make sure you remove the bulbs from underground or it will keep growing back. The Star of Bethlehem in my garden is now starting to show white flowers. This plant has also moved into my lawn. The plant will go dormant and disappear in summer.
garlic mustard (Alliaria petiolata) is another invasive weed that is now blooming. Its leaves are more rounded and form rosettes near the ground in the first year of growth. Sending out a flowering stalk, the leaves become more triangular and heart-shaped with serrated edges. The small white flowers have four petals.
Remove flowering plants and secure in plastic trash bags to prevent seeds from spreading. Prioritize your time to pull out flowering garlic mustard to save labor in the future.
Watch out for sea buckthorn, mulberry and boxwood seedlings in your beds as they are easy to uproot as seedlings. One of the best times to weed is when the soil is wet to get more roots.
For more plant advice, contact the Plant Information Service at the Chicago Botanic Garden at firstname.lastname@example.org. Tim Johnson is Senior Director of Horticulture at the Chicago Botanic Garden.