10 Season-Extension Strategies

Season extension through protected cultivation—growing with methods and materials that moderate the weather—is a universal component of horticultural production. Hoophouses/high tunnels, low tunnels, row covers, and mulches are widely used on market farms and homesteads because of the tremendous benefits they offer. You can use these materials and methods to harvest earlier in spring and later in fall, extend and stagger the harvest of most crops, improve appearance and eating quality, protect against pests and diseases, and increase yields. Indeed, they can be used not just to extend growing into the shoulder seasons but to enable four-season production.

Here Agribon and irrigation provide an insect barrier as well as helping to cool the soil for a newly planted seed crop requiring a lower temperature for optimal germination, while daytime temperatures are still relatively high in late summer.

Row covers come in a range of thicknesses that can serve different protective functions: moderating temperature changes, mechanical damage and drying effects of wind, and excessively bright sunlight, as well as excluding pests.

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Most important, protected cultivation strategies can help you spread out your workload over time. That means less stress and burnout in summer's heat, more enjoyable farming in pleasant weather. For those who farm for a living, season extension helps increase revenue. Most growers who adopt these practices are pleased by the additional income derived from the relatively low investment in these structures and products.

Protected cultivation does add a level of complexity to a vegetable farm or homestead, but it's a challenge that most growers enjoy. You may need to adjust your thinking about some of the many elements of farming. The frost-free date becomes less critical, while day length becomes more important. Large plantings can be replaced by numerous smaller plantings in various environments, or successive plantings. You may even start to grow crops that you had never previously considered or had never before thrived in the field for you.

At Johnny's Research Farm in Albion, Maine, we are continually trialing products and varieties to identify the best combinations for protected cultivation. You'll find the season-extension products you need here on our website and in the catalog. Below, we introduce 10 ideas for achieving season extension. These are suggestions for getting started — as you explore alternatives to field production on your own farm or backyard garden, you will likely discover new ways to improve your crops, increase your income, and enjoy your work more fully.

Shade cloth, too, comes in a range of mesh sizes to accommodate different crops and seasons. Here shade cloth is used to cool the ambient temperature and protect young lettuces from harsh midday sunlight.

Season-extension materials are highly versatile. Most have more than one application for moderating conditions and extending production across seasons.

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1. Plant cold-loving crops in a high tunnel in January and February, and cover with row cover on hoops.
2. Seed leeks in a cold frame in January or February, and transplant them into a low tunnel as soon as the soil can be worked.
3. Start cool-weather crops in a low tunnel two to three weeks before you plant them unprotected in the field.
4. Plant cucumbers and tomatoes in a high tunnel a month before field planting.
5. Plant eggplant in low tunnels covered with lightweight row cover to protect against flea beetles.
6. Put shade cloth on hoops in summer and plant heat-tolerant lettuces.
7. Lay shade cloth on the soil for a week before planting fall crops, to improve germination while the weather is still hot.
8. Keep heavy row cover on hand in case of a late (spring) or early (fall) frost.
9. Plant spinach and carrots in the hoophouse, in quantities sufficient to harvest throughout the winter.
10. Plant spinach in low tunnels to overwinter; it will resume growth in late winter/early spring to produce the first crop of the new season.

Season extension is possible for growers at any scale. For home gardeners, low tunnels and cold frames are a cost-effective alternative to high tunnels for winter harvest and winter growing.

DIY Cold Frame • Easy How-to Tutorial with Niki Jabbour

Winter Growing & Overwintering Resources

• Winter Growing Guide: Winter Harvesting & Overwintering for Spring Harvest  •  Article Series
• Guide to Overwintering Flowers  •  Article Series
• Guide to Forcing Flower Bulbs  •  Article Series

Summer Growing Season Extension Resources

• Beat the Heat  •  Article Series
• Shade Cloth  •  Comparison Chart (PDF)
• Planting Programs • Succession Planting Recommendations by Crop •  Article Series
• Principles & Practices of Succession Planting • Article & Charts

• Johnny's Greenhouse & Tunnel Supplies • Product Listing
• Protect Your Crops • Basic High and Low Tunnel Components• Article
• Row Covers • Comparison Chart (PDF)