In agriculture

Agriculture

Agriculture is the cultivation of animals, plants, fungi and other life forms for food, fiber, and other products used to sustain life. Agriculture was the key implement in the rise of sedentary human civilization, whereby farming of domesticated species created food surpluses that nurtured the...

, season extension refers to anything that allows a crop to be cultivated beyond its normal outdoor growing season.

For colder climates, the fully heated and artificially lit greenhouse

Greenhouse

A greenhouse is a building in which plants are grown. These structures range in size from small sheds to very large buildings...

 is the ultimate season extension device, allowing some crops to be grown year-round, through sub-zero winters. An energy-expensive approach. There are many other ways to beat the cold, for earlier spring planting and growing into the fall and winter:

• Row cover
  Row cover
  In horticulture, row cover is any material used as a protective covering to shield plants, usually vegetables, primarily from the undesirable effects of cold and wind, and also from insect damage....
  
  s: Light fabric placed over plants retains heat and can offer up to several degrees of frost protection. In smaller gardens almost any type of cover, including newspaper cones, miscellaneous bits of plastic, etc., can serve the same purpose.
• Hoop house
  Hoop house
  A hoop house is a greenhouse with a plastic roof wrapped over flexible piping. The interior heats up because incoming solar radiation from the sun warms plants, soil, and other things inside the building faster than heat can escape the structure...
  
  s: Plastic sheeting is placed over a frame (usually in an arced shape), to create a type of greenhouse. Hoophouses can be large or small, simple or nearly as functional as greenhouses.
• Cold frame
  Cold frame
  In agriculture and gardening, a cold frame is a transparent-roofed enclosure, built low to the ground, used to protect plants from cold weather. The transparent top admits sunlight and prevents heat escape via convection that would otherwise occur, particularly at night...
  
  s: Transparent-roofed enclosure, built low to the ground, used to protect plants from cold weather. Cold frames are found in home gardens and in vegetable farming. They are most often used for growing seedlings that are later transplanted into open ground.
• Mulch
  Mulch
  In agriculture and gardening, is a protective cover placed over the soil to retain moisture, reduce erosion, provide nutrients, and suppress weed growth and seed germination. Mulching in gardens and landscaping mimics the leaf cover that is found on forest floors....
  
  es: Any material placed on the soil around plants will help retain heat. Organic mulches include straw, compost, etc. Synthetic mulches, typically, plastic sheeting with slits through which plants grow, is used extensively in large-scale vegetable growing.
• Raised beds: Beds where the soil has been loosened and piled a few inches to over a foot above the surrounding ground heat up more quickly in spring, allowing earlier planting.

Season extension techniques are most effective when combined with crop varieties selected for the extended growing conditions. Many approaches are used in large-scale agriculture, as well as in small-scale organic farming

Organic farming

Organic farming is the form of agriculture that relies on techniques such as crop rotation, green manure, compost and biological pest control to maintain soil productivity and control pests on a farm...

, and home gardening.

Using unheated, unlit methods, depending on the crop, up to several weeks of productivity can be added, where shortened period of sunlight and cold weather end the growing season.

Season extension can apply to other climates, where conditions other than cold and shortened period of sunlight end the growing year (e.g. a rainy season).