I am having a terrible time keeping up with the weeds in my garden this year. Is there a biological difference between a weed and an ornamental plant?
— Jennifer Jacobson, Wheeling
The staff at the Garden is also dealing with a robust weed population to remove this spring. As soon as they are pulled, more seem to appear. Lots of rainy weather has reduced the time the staff has been able to work, while promoting very heavy weed growth. Chickweed seems particularly happy this year. I define a weed as a plant that is growing where it is not wanted in the garden. Different gardeners have different ideas as to what constitutes a weed in the garden. For example, to some gardeners, violets in the lawn are weeds, but to others, those same violets are nice seasonal color accents. Dandelions are widely recognized as weeds, however, their peak flowering time in early spring is when many bees and other pollinators emerge and use dandelions 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 nonnative and are able to establish themselves within existing native plant communities. They pose a threat to the integrity of the plant community. When 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 area that requires continual management for native communities to thrive. Buckthorn is a common weed in home gardens too.
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, and seeds that germinate quickly. These invasive plants have escaped from natural enemies and are able to reproduce vegetatively. Use regional resources for guidance regarding invasive plants. The Chicago Botanic Garden has an invasive plant policy that can be accessed on the Garden’s website to help you avoid choosing an invasive plant for your garden.
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 grow within clumps of perennials and spread to other others when dividing and transplanting. I have sprayed patches of it in my garden with an herbicide four times so far this 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 get the bulbs out) or it will continue to grow back. This plant has moved into my lawn too. The plant will go dormant and disappear in summer. 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 in order to get more of the roots out is when the ground is moist.
