Early frosts are fast approaching

  • To protect your fall mums or flowers from early frosts, cover them with sheets, plastic or boxes.

    To protect your fall mums or flowers from early frosts, cover them with sheets, plastic or boxes. Courtesy of Chicago Botanic Garden

By Tim Johnson
Chicago Botanic Garden
Posted10/13/2019 7:00 AM

The average first frost at the Chicago Botanic Garden is Oct. 15, though it is typically later in Chicago. Tender plants can be protected from light freezes by covering them with sheets, plastic or boxes.

When night temperatures begin dropping below 40 degrees, it is time to bring in any tropical plants you are keeping outside. A gradual decline in temperatures over a period of time is best, as the plants will acclimate some to the cooling weather.


You may want to move the tropical plants in for a night if there has been a long spell of warm weather and a sudden dramatic drop in temperature is predicted.

• Warm fall days are great for installing Christmas lights, though most people do not think about installing lights until after Thanksgiving. It is much easier to wrap branches with strings of lights on warm days in mid- to late October versus cold days in late November or early December.

Use LED lights to save on power and be able to use more strings on a circuit. Buy warm color white LED lights if you want to match the color of the commonly used white incandescent lights. Cool color LED white lights will have a blue cast to them.

The Chicago Botanic Garden staff starts installing strings of lights in early October. You may be able to leave lights on your trees for a couple years to save time. As the tree grows, the lights will tighten so will need to be reinstalled.

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Wrap branches of your trees with strings of lights to accent the tree's form. Be sure to use power cords that are rated for outdoor use.

• If you want to save your coleus for next year, then this is a good time to take cuttings that are 4- to 6-inches long and root them. Simply put them in water, removing any lower leaves that will be in the water and pot them up once they form roots. Grow these plants outside until the temperatures begin dropping into the 40s. Keep them in a sunny window for the winter, pinching the plants back as needed.

• Tim Johnson is director of horticulture at Chicago Botanic Garden, chicagobotanic.org.

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