We can expect to see changes in our landscape plants in the coming weeks. The obvious one will be fall color as the weather pattern continues to move from summer to fall conditions. If you are seeing strong fall color already in a plant, there is likely a health issue going on. Anytime we have premature fall color, there is often structural damage either above ground or below it, or the plant is suffering from severe stress from another cause. Before that, the changes may not be quite as easy to spot. By now, all woody plants will have generated foliage and flower buds for the spring of 2018. You will be able to detect slight changes in the green leaves too. Those leaves are not going to be that shiny green they have been. Plants also will be setting up the abscission layer at the base of the leaf petiole and the stem they are attached to, allowing the leaves to come down giving us yet another fall yard task – raking up the leaves – but that is weeks away yet!
Our lawns being a cool season grass are actively growing roots again after the summer weather, which naturally slows them down. What happens in the lawn this fall directly influences how well the lawn overwinters and the spring flush in 2018. If you only fertilize once a year, fall is the better time. September through early October is a good window. We used to be able to buy a "winterizer" lawn fertilizer, but with the lawn fertilizer regulations prohibiting the addition of phosphorus to the lawn, this is not as common as it used to be. The frequency of cutting your yard is going to pick up for a short while, then taper off again, but continue to mow well into the fall to keep from leaving the lawn too long for the winter.
Perennial herbaceous flowers are doing what other woody plants are, getting food down into the crown, tubers, root systems, and bulbs for next year. You will see changes to the foliage as well. It is common to see leaf spots move in, another sign that fall is on the way. Most gardeners wait to clean the beds until all the plants are ready, yet if your time is limited, you can clear those plants as they fade away and add the plant debris to the compost pile a bit at a time.
September and October should bring us adequate water to help our plants prepare. One of the best garden tasks late in the season is to water any evergreens, newly planted trees, shrubs, and perennials to ensure the soil moisture is there for the winter. So before you take the garden hose off the spigot, make your rounds. Then you get to drain and store the hose for the rest of the winter.
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" on Facebook at facebook.com/extensiondkk/videos. The 2017 Kendall County Master Gardener Help Desk currently is open Monday, Wednesday and Friday from 9 a.m. to 12:30 p.m. at 630-553-5823 or at uiemg-kendall@illinois.edu.
About the author: Richard Hentschel’s expertise extends across several subject areas with specialties in lawn care, fruit tree production, woody ornamentals, and home and community gardening. During his 45-year career in horticulture and agriculture, Hentschel became a well-known and respected expert for commercial and homeowner audiences, industry organizations, and media. He retired from University of Illinois Extension in April 2022 with nearly 30 years of service as a Horticulture Specialist and Educator in northern Illinois.