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The summer months keep gardeners’ tables filled with lots of fresh produce. Fortunately, using some season-extension techniques, Oklahoma gardeners can keep that fresh taste on their table for a while longer. The bonus is gardeners don’t have to have their own greenhouse.


Many folks tend to think of gardening season just through the summer months, and perhaps into early fall. However, season-extending techniques will help gardeners harvest greens and other cool-season crops into the winter months. As an added bonus, these techniques even can help gardeners get a jump start on warm-season vegetables earlier in the spring.


Basically, season extension involves providing favorable plant growth conditions on a day-to-day basis and protecting plants from brief events that can cause serious damage, such as an early fall freeze. Have you ever been in a greenhouse? No matter what time of year it is, the temperature is warm in a greenhouse. So, how is a gardener supposed to get green-house-like temperatures at home without a greenhouse?


One way is called low tunnels. This technique involves fabric row covers suspended over the crops and will protect plants from wind and precipitation. Use clear polyethylene or other sheeting and place over the plants in your garden. The sheeting is supported by wire or plastic hoops and the plastic is vented to prevent excessively high temperatures.


The high tunnel method, or hoop house, is one that can extend the fall growing season or help get an earlier start on warm-season crops in the spring. This method provides an enhanced growing environment and protection from frosts, late freezes, hail, wind and heavy rain. There are a variety of options for structure designs.


Another option is what is called a cold frame. Cold frames are structures outside of the garden where plants can be placed for temperature modification and protection from rain, snow and ice. This is used to force spring-flowering bulbs, harden transplants, start cold-tolerant transplants and overwinter semi-hardy plants.


By adding a heat source, gardeners can expand the use of cold frames. The heat source is added below the soil, making them hot beds. Heat sources can include electric heating cables, pipes carrying steam and composting organic material below the soil.


A garden cloche is a way to modify the environment for individual plants or groups of plants. Gardeners create warmer growing conditions to protect plants from brief cold exposure. Think of it as an individual little greenhouse.


While season-extension techniques help increase temperatures that are favorable for plants, keep in mind light also is a limiting factor during the cool months. In the winter, solar light intensity is low, and the days are short. This is why it’s important to place structures where they’ll receive as much light as possible.


For more information about season extension, check out Oklahoma State University Extension's Master Gardener's Manual.

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