- Agribon+ AG-19, 30, 50 & 70 Row Cover | Insert (PDF)
- Pest & Disease Control Basics in Greenhouse, Hydroponic & Other Protected-Culture Systems
- QuickHoops Gothic High Tunnel Bender | Construction Manual for Modular Moveable Gothic High Tunnel (PDF)
- QuickHoops Gothic High Tunnel Bender | Construction Manual for Stationary Gothic High Tunnel (PDF)
- QuickHoops Elliptical High Tunnel Bender | Construction Manual for 24'-Wide High Tunnel of Any Desired Length (PDF)
- QuickHoops High Tunnel Bender | Construction Manual for Building a Stationary High Tunnel (PDF)
- QuickHoops Low Tunnel Benders | Instruction Manual (#9377 & #9520) | (PDF)
- Hitch Mount for QuickHoops Low Tunnel Benders | Instruction Manual (PDF)
- Bobcat Automatic Ventilation Kit Manual (#6791) | Tech Sheet (PDF)
- Bobcat Basic High Tunnel Kit Manual (#6923) | Tech Sheet (PDF)
- Bobcat Basic High Tunnel Kit (#6923) | Parts List (PDF)
- Bobcat Pro High Tunnel Kit Manual (#6794) | Tech Sheet (PDF)
- Bobcat Pro High Tunnel Kit (#6794) | Parts List (PDF)
- Bobcat Sliding Door Kit Manual (#6792) | Tech Sheet (PDF)
- Bobcat Standard High Tunnel Kit Manual (#6795) | Tech Sheet (PDF)
- Bobcat Standard High Tunnel Kit (#6795) | Parts List (PDF)
- Bobcat Steel End Wall Kit Manual (#6793) | Tech Sheet (PDF)
- Truss Support Kit Manual (#6790) | Tech Sheet (PDF)
- Bobcat Tunnel Kits | Comparison Chart
- Beginning & Intermediate Controlled Environment Agriculture (CEA) | Advances in Greenhouse Crop Production
- Hoop Loops | Installation Instructions | Tech Sheet (PDF)
- Protect Your Crops | High & Low Tunnel Basics
- The Effect of Shorter Daylength on Winter Production
- Be First & Last to Market by Extending Your Growing Season
- Planning for Opening Day at the Farmers' Market or for Wholesale Accounts
- Quick Hoops Low Tunnels | Set-up & Management with Eliot Coleman
- Constructing the Modular Moveable Gothic Tunnel – Animated Schematic
- Moving the Modular Moveable Gothic Tunnel – Slideshow
- Skinning the Modular Moveable Gothic High Tunnel – Slideshow
- Overwintering Vegetable Crops | Planting Chart
- QuickHoops Moveable High Tunnel Bender | Instruction Manual (PDF)
- QuickHoops Seedling & Microgreens Bench | Construction Guide (PDF)
- Why Grow in a Greenhouse? Basics & Advantages of Protected Culture
- Recommended Varieties from Our Greenhouse Trials | What We Look For in Greenhouse Crops
- QuickHoops 3'W x 4.5'H Low Tunnel Bender (#7616) | Instruction Manual (PDF)
- Cable Purlin Trellis for QuickHoops High Tunnels | Installation Manual (PDF)
- Row Cover & Insect Netting Options & Uses | Comparison Chart (PDF)
- Tufflite IV Greenhouse Film | Comparison Chart (PDF)
- Univent Automatic Opener for BiFold Doors | Instruction Manual (PDF)
- Video: Johnny's Season Extension & Overwintering Trials
- Video: Take a Tour with Us of Johnny's Greenhouses!
- Video: Planning & Planting the Autumn Vegetable Garden | Tips & Recommendations with Niki Jabbour
- Video: How to Use Quick Hoops™ Benders to Create High & Low Tunnels
- Video: The Benefits of Row Covers | Recommendations & Tips from Johnny's Selected Seeds
- Video: Hoop Houses & Other Ways to Extend Your Growing Season
- Johnny's Winter Growing Guide | Printable 10-pp Brochure (PDF)
- Winter Production in the High Tunnel | Johnny's Winter Growing Guide
- Winter Growing Guide | Introduction & Part 1: Scheduling Your Winter-Harvest High Tunnel
- Winter Growing Guide | Protection Methods for Overwintering in Low Tunnels
- Winter Growing Guide | Scheduling Guidelines for Overwintered Crops
- Winter Growing | Recommended Crops & Varieties
- Winter-Harvest Crops | Planting Chart | Calculator for a Seamless Winter Harvest
- Pests & Diseases of Greenhouses & Hydroponic Systems | Tech Sheet (PDF)
- Video: Growing Under Cover with Niki Jabbour | Johnny's Webinar Series
- Growing Under Cover with Niki Jabbour & Johnny's | Johnny's Educational Webinar Series
- Overwintering Onions from Seed | Johnny's Selected Seeds
- 10 Ways to Extend Your Season with Protected Cultivation
A Guide to Winter-Harvest Crops & Overwintering for Spring Harvest
Introduction to Winter Growing
Here at Johnny's Research Farm in Albion, Maine, the Persephone period begins on November 6th.
It ends on February 6th, when daylight at our latitude again reaches 10 hours in length.
When temperatures drop and daylength dwindles, your harvest season need not come to a full stop. As more growers add high and low tunnels to their operations and participate in winter markets, we are frequently asked:
“ What can I plant to harvest in winter, and when should I plant it? ”
Producing marketable crops in winter requires learning the correct planting window dates for your location. We've developed this guide to provide a starting point, primarily for growing within unheated tunnels. You can use the charts and guidelines presented here while adjusting the techniques and timing to fit your own region and practice. Remember to keep records, to determine what works best and improve upon your successes.
To begin, it is helpful to distinguish between the two basic winter growing strategies. The first group you harvest in winter, the second group you leave in place over the winter to produce an early spring crop.
- Winter-Harvest Crops are planted in late summer or early fall, primarily in high tunnels, for harvest throughout the winter.
- Overwintered Crops are planted in the fall or winter, often outside in the field or under low tunnels, and left in place for the earliest possible spring harvest.
Note that there may be no real bright line between them in your system, but we suggest conceptualizing them separately as a way to create a production timeline. There is plenty of flexibility and overlap in the methods employed, and many growers combine methods and practice succession planting to achieve four-season production.
Scheduling Guidelines for Planting the Winter-Harvest High Tunnel
Ten hours of day light
The key to scheduling your winter-harvest plantings is to identify the date by which your day length has decreased to 10 hours on its trajectory to the winter solstice. It is during this darkest time of the year — referred to by Eliot Coleman as the Persephone period — that growth slows to a glacial rate for most crops.
The goal is to seed your plants so they are about 75% mature by the time you enter the Persephone period.
Though plants may not grow appreciably thereafter — that is, until day length has again increased to 10 hours plus — they can be harvested as needed as long as their maturity holds.
Careful scheduling allows you to control growth incrementally by planting at least two or three sowings at 7–10-day intervals, decreasing the time between plantings down to 2–5 days as you approach the Persephone period. Staggering the plantings in this way allows for crops to mature at different times and provide a longer harvest period. You might want to seed on September 20, September 27, and then October 1, for example. With well-timed, staggered plantings you can create a smooth transition from one harvest to the next for a steady supply through the winter. Multiple seedings also help you identify the best seeding dates for specific crops (which you could then record) and spread out the risk of crop failure due to unfavorable weather conditions.
Two neat tricks to get plants ready for the darkest days in high or low tunnels
- Transplant crops like spinach that are normally direct-seeded. Start the plants elsewhere and grow them to transplant size before planting them in your high tunnel, after your summer-producing/summer-fruiting crops have been removed.
- Establish hardy crops outside in late summer, then place a moveable tunnel over them or construct a caterpillar tunnel over the crop as winter draws near.
Squeeze in even one more crop
Anticipate and plan for any open bed space that may become available in late winter, once you have harvested your winter crops.
- Some crops, like lettuce, will be finished in early to mid winter.
- Other crops, like mustards, will bolt coming out of the Persephone period, so they'll be finished then. As the end of the Persephone period draws near, they can, for example, be replaced with direct-seeded spinach or brassicas.
These late-winter sowings will be ready for harvest by early spring, often long before the same crop would, had it been grown outside.
- Intro to Winter Growing
- Scheduling Guidelines for the Winter-Harvest High Tunnel
- Winter-Harvest Crops • Planting Chart
- Winter Production in the High Tunnel
- Overwintering Scheduling Guidelines
- Overwintering Crops • Planting Chart
- Protection Methods for Overwintering in Low Tunnels
- Focus on Crops & Varieties for Winter Growing
- Overwintering Onions from Seed