All this cooler weather especially at night is having an effect on all our plants in the landscape. The temperatures we have been having at night especially have caused changes in how the plants have switched from actively growing to getting ready for dormancy. The plants used as annuals or as garden accent plants that are really tropical, would never go dormant in their native habitat and have responded immediately to the cold nights. If you have grown Elephant Ears or see them in public plantings, they have taken on a wilted kind of look, even though they have plenty of water. The new tropical this year has been a yellow and green Alocasia in many subdivision entryways along with dwarf banana. Calla Lilies are doing the same thing, listing over outside the edge of the bed. These kinds of plants and all the other summer flowering bulbs that are planted for visual summer impact in gardens will have to be dealt with before a strong frost or light freeze. Summer bulbs will need to be dug up and allowed to dry before you can store them in a cool dry location for the winter. Gardeners will often set them in a flat and lightly cover the summer bulbs with a slightly moist soil sand mix or a damp commercial potting soil. Tropicals like Elephant Ears, Amaryllis and Alocasia will be handled in a similar manner. These tropical's can be left in their pots if the containers are of a manageable size and placed in the same conditions as summer bulbs. The idea is to keep them dormant at a temperature above freezing, cool enough that they will not start to grow and not allowed to dry out or be too moist.
Our deciduous plants in the home landscape begin to start the dormancy process as we have cool nights and warm days. Visually we see this change in how the foliage looks. Glossy green leaves will lose the shine. Less chlorophyll is produced, revealing colors in the leaf that have been masked throughout the summer. Lots of plants will show a yellow fall color, others orange or red depending on the plant family. For example Maples often show strong orange and red colors, Oaks will turn a brown due to all the tannins in the leaf. One of our more popular plants, Dwarf Burning Bush turns that bright fire red, while the species version of Burning Bush is multicolored, having yellow, pink and red on the same plant over a period of several weeks.
Internally, the cooler temperature signals the plant to move nutrients into the root system to be available for growth next spring. This is going on as you see the color change in the leaves. Some of the last food produced stays in the foliage stems and branches. When the food stays in the leaves, it adds to the fall color. The food that remains in the stems and branches is there to supply the food to the newly emerging buds next spring. As the flow of food from the root system returns, it continues to feed those new buds. There will be some root growth from our plants until the soil gets too cold for even the roots.
If you have doubts about our weather, farmers have started to harvest the early varieties of corn already.
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.