When to Plant Which Winter Vegetables

by Julia Frisbie

posted July 29, 2021

If you’ve stashed your seed packets away for the year, you’ve done it too soon. There’s still time to plant lots of winter vegetable varieties here on Fidalgo Island. To be successful, you need to be aware of the way that decreasing daylight slows and stops plant growth over winter.

Elliot Coleman writes in The Winter Harvest Handbook, “As the story goes, the earth goddess Demeter had a daughter, Persephone, who was abducted by Hades to live with him as his wife in the netherworld. Demeter would have nothing to do with this and threatened to shut down all plant growth. Zeus intervened and brokered a deal whereby Persephone would spend only the winter months with her husband, Hades. Demeter, saddened by her daughter’s absence, made the earth barren during that time. On our farm we refer to the period when the days are less than ten hours long as the Persephone months.”

Daylight hours depend on latitude. Coleman notes how, on his farm at 44 degrees north, the Persephone season coincides with two of the holidays of the pagan agricultural calendar of the ancient British Isles, beginning around Samhain (early November), and ending around Imbolc (early February). Most of us don’t celebrate holidays by those names anymore, but we are aware of their modern counterparts: Halloween and Valentine’s Day. We’re at 48 degrees north, so our Persephone season is just slightly longer than Coleman’s, and lines up almost perfectly year-to-year with the modern holidays. Here’s a graph of our 2021 daylight hours from timeanddate.com:

Hours of daylight per 24 hour period are on the Y axis of this graph, so you can see that we have more than 10 hours of daylight per day from mid-February until late October. Those are the times when plants can do enough photosynthesis to put on significant new growth. With less than 10 hours of daylight, I notice that most of my frost-hardy plants are in a sort of suspended animation: they’re not suffering, they’re not shrinking, but they’re not growing much.

Despite having a slightly longer Persephone season, our winter gardens have one major advantage over Eliot Coleman’s: mild temperatures. Surrounded on every side by the approximately 50-degree water of the Salish Sea, our gardens stay warm(ish) and aren’t blanketed in snow for more than a week or two each winter. They may get a touch of frost overnight, but not too much for the sunshine to thaw out by midday. Most of the time, our outdoor winter temperatures are similar to the inside of your fridge.

What that means is, if you grow frost-hardy plants to a harvestable stage before the Persephone season starts and they go into suspended animation, you can treat your garden as a “living refrigerator” all winter long. I am borrowing this term from Mother of a Hubbard, one of my favorite garden bloggers. She has built low tunnels in her garden, and covered them with a frost blanket. I’ve tried that, but no matter how well I secure the fabric, our winter storms always blow it away. Many plants do fine even after the fabric has escaped and wrapped itself around the next door neighbor’s mailbox, so unless you’re a true infrastructure genius, I’m not sure the fabric is worth bothering with.

The seed packets in your collection should note frost hardiness, along with days to maturity. The latter can be used to calculate whether or not there’s still time to plant it before the Persephone season. Note that growth slows down before it stops, so I always try to give fall-maturing plants an extra 30 days in the ground beyond what their seed packet indicates.

Here’s the calculation I use:

Next week I’ll write more about the veggies that feed my family all winter. I’m eager to hear what’s worked for you, too! Leave a comment with your best winter veggie varieties, and I’ll include your recommendation in next week’s post.