All the soil moisture that has the home landscape looking so good right now also encourages any perennial weeds, whether grasses or broadleaves, to grow vigorously too. In the lawn, Master Gardeners are answering questions on tall fescue and quackgrass for both identification and potential management. Since they are perennial grasses just like our preferred lawn grasses, options are limited to post-emergence products that will take out these grassy weeds right along with our lawn grasses. Gardeners have some good success managing tall fescue by digging out this bunch-type grass and reseeding or sodding the spot. This is not a good option for quackgrass, as it has a spreading underground root system.
Common broadleaved weeds in the lawn include dandelion, plantain, ground ivy (known as creeping Charlie) and more recently thistles. The first line of defense is getting and keeping the lawn competitive against these weeds. Treatment of the weeds and getting the lawn strong can be done at the same time. As the weeds fail, vigorously growing turf will fill in.
Of all the thistles, the worst one to manage is Canadian thistle. It spreads by underground rhizomes just like quackgrass. If you see several thistles "in a row," they are very likely coming up from the same below ground runner. Thistles show up in the lawn from areas that are not managed. If thistles are left to grow, they will produce seed and can spread that way too.
In the perennial beds, all of the above weeds can be present. Dandelions can be growing up in the crown, as that is where the weed seed was caught. It is common to see grasses growing up and out of the canopy of your perennials and dandelion from at the base at the same time. Once you decide it is time to clean that up, digging up the perennial at the right time and clearing the roots of the grassy weeds and taproot of dandelion before resetting is a good practice. This is also a good time to check for soil insects, such as the iris borer, if you cleaning up and dividing plants.
In the vegetable garden, every time you work the soil, you encourage a new crop of weed seed to germinate. If you do need to cultivate, do so very shallowly. You can exhaust the supply of weed seed after several times of shallow cultivation and then the canopy of vegetable plants will continue to shade the soil, further reducing weed seed germination. If you do need to water the vegetable garden, water the base of the plants or along the row. Watering the whole garden will encourage weed seed to germinate as well.
Richard Hentschel is a Horticulture Extension Educator with University of Illinois Extension, serving DuPage, Kane and Kendall counties. Stay tuned to more garden and yard updates with This Week in the Garden videos at facebook.com/extensiondkk/videos and the Green Side Up podcast at go.illinois.edu/greensideup. The Kendall County Master Gardener Help Desk is open for 2018. Current hours are Monday through Friday from 9 a.m. to 12:30 p.m. at 630-553-5823.