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Johnson County

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Johnson County
11811 S. Sunset Drive
Suite 1500
Olathe, KS 66061

Office Hours:

Monday - Friday,
8:30 a.m. - 5 p.m.

(913) 715-7000
(913) 715-7005 fax

Map to our office

K-State Research and Extension is committed to making its services, activities and programs accessible to all participants. Reasonable accommodations for persons with disabilities may be requested by contacting Johnson County Extension at (913)715-7000. Notify staff of accommodation needs as early as possible.

Kansas State University Agricultural Experiment Station and Cooperative Extension Service

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Season Extension Methods

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“Season extension,” as vegetable growers know it, is the practice of prolonging the growing season of your plants by protecting them from frost or freezes. Typically, in this region, we will see the first frost of the season sometime between mid-October and mid-November. However, with the area still bearing the signature unpredictability of Midwest weather, that frost could be followed by several more weeks of ideal growing conditions for your garden. So, how do we protect the plants during that one frost event to keep them going afterward?

The key factors to consider when practicing season extension are the outdoor temperatures, microclimate, and airspace around the plants. If an area is particularly prone to harsh windchills, the plants will feel the effects. If an area is protected from wind on all sides, with stale, non-moving, warmer air settling in the location, the plants will also likely be warm. Taking all these aspects into consideration can assist us as we pinpoint when and where cooler temperatures may be too much for plants to handle without mitigation.

Depending on variety selection and the type of crop being worked (cool season crops will be much more cold-tolerant and less tender than warm season), the utilization of “hot caps,” cloches, and garden covers can be incredibly useful for prolonging the life of your plants.

Summarized, these gardening tools act as “caps,” protecting plants from cold weather. Often, they can be as simple as a milk jug with the bottom cut out or an overturned bucket or bowl placed over the plants being protected. The garden covers could be as simple as a sheet with its edges pinned down.

The critical component of all these tools is that they provide a microclimate for your plants to exist where one may not exist naturally. Sun is still allowed through; the inner air is kept stale and still, allowing warmth and humidity to surround the plants. This helps keep them alive instead of windchill and frost harming them.

However, some key points must be remembered for success in using these tools.  The edges of your hot caps or cloches should not be touching the plants themselves, as the edges of the containers will still reach freezing conditions. As such, any plant material contacting the containers' edges is also prone to damage. If the outside temperatures drastically warm up during the day, your plants will likely wind up steamed or cooked without ventilation or completely removing the hot caps. Attention to your plants' conditions must be consistent to make appropriate adjustments.

When season extension is done correctly while utilizing the appropriate plants, you can extend your growing season into early winter and keep your garden production going until the first hard freeze.


K-State Research and Extension Johnson County Master Gardener logo

Have questions? The Garden Hotline is staffed by trained EMG volunteers and Extension staff who will assist you with questions.

Phone: (913) 715-7050

Email: garden.help@jocogov.org