Patrick Byers is a regional horticulture specialist with University of Missouri Extension, headquartered in Springfield, Mo. He provides horticultural outreach activities to 16 counties.
 

 
 

Better Late than Never
by Patrick Byers - posted 08/01/17

Root vegetables such as turnip, beet, carrot and radish are mainstays of the cool-season garden.


Traditionally, the Midwestern vegetable garden was considered a three-season affair, bounded by the last spring frost and the first fall freeze. True, cool-season gardens were popular in the spring and the fall, but the idea of year-round vegetable production definitely raised eyebrows. Recently, however, proponents of season extension, such as Elliot Coleman, have increased awareness of the possibilities, and enthusiastic gardeners across the region are embracing four-season vegetable gardening.


Plan Ahead
The first step is to plan the late-season garden. Basically, vegetables may be divided into three categories: warm-season vegetables that are damaged by even light freezes, cool-season vegetables that tolerate light to moderate freezes, and those hardy vegetables that can tolerate even extreme-cold temperatures with some protection. While gardeners can protect warm-season vegetables such as tomato, pepper and eggplant from the first autumn frosts, at some point, the useful life of these vegetables will end. Thus, the late-season garden will focus on cool and cold-season vegetables that thrive under shorter days and lower temperatures.


Heavyweight row cover can provide protection from winter conditions. Note the wood lathe used to anchor the edges.


Planting Date
The planting date is a critical component of success with the late-season garden. In many cases cool- or cold-season vegetables must have a period of warmer temperatures during which seeds germinate and plants grow to a useable size. Take cole crops, for example. Broccoli and cabbage for the late garden are generally seeded in July, and the seedlings are transplanted into the garden in August. Even cold-season vegetables such as hardy salad greens and root vegetables are usually direct seeded in August and September. Growth of these vegetables slows or even stops when cold weather arrives, but if planted at the proper time, the vegetables are at the optimum stage for delicious harvests, in some cases with a little protection, for the remainder of the fall and winter.


This homemade high tunnel is constructed from a cattle panel fence covered with a single layer of plastic. The ends are closed during cold weather.
 

Protective Structures
While many cool- and cold-season vegetables will happily survive light frosts and produce in the open garden, a true four-season gardener relies on protective structures for winter-long harvests.

Row covers are sheets of breathable polypropylene fabric that provide temporary protection for plants and are placed over vegetables during cold weather of shorter duration. Choose heavyweight row covers (at least 1.5 ounces per square yard), and anchor the edges to hold the covers in place.


Serious winter gardeners can consider a passive solar greenhouse for winter production. Note the large black barrels of water, which trap solar energy during the day.
 

A low tunnel is constructed from row cover or plastic sheets, supported over the plants on a series of hoops. Low tunnels allow for plant survival and growth during extended cold periods. Low tunnels can stay in place for the duration of the winter, and crops are harvested from the side of the tunnel.

A cold frame is a bottomless structure put over plants, with a glass or clear plastic cover. The cover can be opened during the day time to allow ventilation. Cold frames are constructed from many materials, such as cinder blocks or dimension lumber. The cover is sloped to shed precipitation and faces south or southwest to capture sunlight during the shorter winter days.


Cold frames are constructed from a range of materials. Raise the cover to provide ventilation on sunny winter days.
 

The high tunnel or hoop house is a frame covered with one or two layers of clear plastic. Vents on the sides or ends can be rolled up to enable excess heat to escape during the daytime and rolled down at night to trap heat so that the environment around the plants is kept warmer. High tunnel kits are available, or do-it-yourself gardeners can construct high tunnels with a support structure and plastic sheeting.

Passive solar greenhouses are the ultimate in season extension, allowing for vegetable production in even the coldest weather without the use of artificial heating. These greenhouses rely on storage of solar energy during the day, often in a mass such as large barrels of water or a masonry wall, which is then released back into the greenhouse during the night. For best results, construct the greenhouse according to plans; sample plans are at aes.missouri.edu/bradford/education/solar-greenhouse/solar-greenhouse.php.

   

A version of this article appeared in a July/August 2012 print edition of State-by-State Gardening.
Photography courtesy of Patrick Byers and Anastasia Becker.
   

 

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