Fall is somewhat of a somber time of the year for gardening enthusiasts, since it usually signals the end of the outdoor growing season.
Based on weather data collected over many decades, there is a 50 percent chance that mid-Missouri’s first frost of the fall will occur on or before Oct. 23. If one increases the probability to 70 percent, the date advances to Oct. 29. In either case, when October arrives, the end of the growing season is near.
It’s important to remember that plants differ in their ability to withstand cool temperatures. Certain species (mainly tropical in nature) suffer “chill injury” at temperatures well above freezing. Most species in this category should not be exposed to temperatures lower than 45 degrees. Since many tropical species are container-grown, they should be brought inside early in the fall, if possible.
Another consideration to remember is that the moisture in plant tissue is not pure water, but it contains solutes which lower its freezing point. Except for sensitive tropical plants, most plants can withstand 28 degrees with little, if any, damage. Cool-season flowers and vegetables (e.g. pansy and cabbage) can withstand considerably lower temperatures, depending on species and the exposure to gradually cooler temperatures.
The philosophy for protecting plants in the fall differs from that for spring protection.
In the fall, gardeners are simply “prolonging the inevitable” when attempting to protect plants from cold temperature injury. Be they ornamentals or food crops, most have served their purpose and provided enjoyment and food for the past growing season.
In the spring, gardeners are protecting an investment they have made in plants which have yet to yield dividends. Therefore, more aggressive (and expensive) protection measures are warranted.
In either case, protection from cold temperatures usually involves attempting to preserve latent heat stored in the soil of a garden or growing medium of a container. Normally, this involves placing insulative materials over tender plants. However, this process likely will result in only a couple of degrees increase under the insulative material versus above it.
Lightweight floating row cover (e.g. AgFabric) is an example of a commercially available product manufactured for frost protection. Old bed sheets, blankets or other items already on hand may be used, but some mechanism of support may be needed to keep these materials from crushing delicate plants.
Fortunately, the soil contains more latent heat in the fall than in the spring. Therefore, protecting plants with an insulative material tends to be more successful in the fall. The insulative material should be removed during the day to allow plants to be exposed to sunshine.
However, there comes a point when gardeners must acknowledge the growing season has ended. It is then when gardeners choose to follow the wisdom of “to everything there is a season, and a time to every purpose … a time to plant, and a time to pluck up that which is planted.” Fall garden cleanup is an important chore that will help to disease and insect infestation the following growing season.
Finally, don’t be discouraged. As Hal Borland wrote, “no winter lasts forever, and no spring skips its turn.” The 2026 growing season is just around the corner.
David Trinklein, Ph.D., is a MU Extension State Specialist and former Director of the Missouri Master Gardener program. He can be reached at [email protected] or (573)882-9631.
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