After years of experimentation, Eliot Coleman concluded that most plants stop growing when the day length drops below 10 hours.  After this time, even if you protect your vegetables from the cold, they are merely existing in a semi-hibernatory state.

Coleman coined the term "Persephone Days" to refer to this deep winter period of short days, which occurs from November 5 to February 5 on his farm in Maine, from December 1 to January 10 in Charlotte, North Carolina, and from about November 22 to January 19 here in southwest Virginia.  Those of you who are lucky enough to live south of the 32nd parallel have no Persephone Days and can keep your crops active all winter if you play your cards right.

The trick to a long winter harvest is to plant your crops at just the right stage of the late summer and fall so that they are just shy of maturity when the Persephone Days begin.  Young plants are much hardier than older ones, so planting dates are even more important in the fall than in the spring --- planting too early is just as bad as too late.  You'll also need to pay close attention to succession planting so that you'll have a continuous harvest throughout the winter rather than a mass of lettuce one week and then no more for the rest of the year.  In effect, you're not extending the growing season, just the harvest season.



I mocked up the chart above based on information in The Winter Harvest Handbook, but converted it over to the type of planting calendar I find so helpful.  Rather than placing the last or first frost date at 0 the way I do with my spring planting and fall planting calendars, I've placed the onset of the Persephone Days there, but the chart is otherwise read in the same manner.  For example, Eliot Coleman's Persephone Days begin November 5, so he plants his first arugula nine weeks before, around September 3.  Since my Persephone Days begin on November 22, I should plant my first arugula on September 20.

You'll also notice that Coleman lists outdoors and greenhouse planting times for many of his crops.  As I mentioned in a previous post, the greenhouse crops don't really need to be covered for a couple of months in many cases, so his "greenhouse-planted" carrots seeded fourteen weeks before his Persephone Days are actually planted in the open, then have a greenhouse moved over top of them in late October.

A word of warning --- all of Coleman's data is for the far northeast, so I expect I'll need to play around with these planting dates by as much as a week or two to find the optimal planting times for my climate.  If you've already developed a planting calendar for winter harvest in the southeastern or mid-Atlantic states, I'd be curious to hear your specifics.

This post is part of our Winter Harvest Handbook lunchtime series.  Read all of the entries: Winter Harvest Handbook Winter garden protection: Greenhouses and row covers Winter garden protection: Quick hoops When to plant for a winter harvest What to plant for a winter harvest

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About us: Anna Hess and Mark Hamilton spent over a decade living self-sufficiently in the mountains of Virginia before moving north to start over from scratch in the foothills of Ohio. They've experimented with permaculture, no-till gardening, trailersteading, home-based microbusinesses and much more, writing about their adventures in both blogs and books.



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