When folks ask me after I plant winter-harvested crops like carrots and kale, they’re usually shocked to study I put these seeds within the floor in late summer season or early fall. And that is smart! It’s straightforward to imagine folks plant these cold-hardy crops in late fall and harvest them a number of months later in winter.
Nonetheless, plant development slows as days grow to be shorter. And as soon as daylight drops under ten hours, a time often called the Persephone interval, plant development virtually stops. By no means heard of this era earlier than? No worries!
I’ll share particulars about this a part of the yr and clarify why understanding it’s necessary for profitable winter rising.
The Brief Reply
The Persephone interval, coined by vegetable farmer Eliot Coleman, happens when the day size drops under ten hours. Crops expertise decreased development throughout this time, so realizing when it happens might help you identify when to plant winter crops.
The Lengthy Reply
We all know the Persephone interval pertains to daylight and impacts plant development, however how precisely do you have to think about it when planning your winter backyard? I’ll share some extra particulars about this gardening time period and canopy how you should utilize it to plant winter crops on the appropriate time.
Midway by the yr, the Earth has rotated midway across the solar. Now, the southern hemisphere tilts in direction of the solar, and the northern hemisphere faces away, resulting in a change in seasons.
However we don’t simply snap our fingers and watch the longest day of the yr remodel into the shortest. As a substitute, we see a gradual shift in day size and a change in seasons. And this modification brings the primary ten-hour day, in any other case often called the beginning of the Persephone interval.
Whereas this era has at all times existed, Maine vegetable farmer and winter-growing pioneer Eliot Coleman coined the time period, which individuals proceed to make use of in the present day. However he didn’t give you the parable of Persephone. No, that was the historical Greeks.
Persephone was the daughter of Demeter and Zeus and the goddess of vegetation. In line with the legend, Persephone was out in a discipline choosing flowers when the Earth out of the blue opened up. Hades, the king of the underworld, appeared out of the crack and kidnapped Persephone. When Demeter realized of her daughter’s abduction, she turned distraught and compelled crops to cease rising as a type of protest. Ultimately, folks turned hungry, and Zeus compelled Hades to return Persephone. When the goddess returned to the floor, plant development resumed.
This delusion gave the darkest a part of the yr its title.
Learn how to Decide
The beginning of the Persephone interval varies relying in your longitude. You may search for a day-length calendar to find out when the primary ten-hour day will happen.
The place I dwell in East Tennessee, day size drops to 10 hours on November 26. Days proceed to lower till the winter solstice on December 21. After the solstice, days enhance till they return to 10 hours on January 16. Which means the Persephone interval in my space happens from November 26 till January 16.
The Position of Mild in Plant Progress
Whereas many individuals assume that chilly prevents us from rising crops in winter, gentle additionally performs an enormous position. Certain, a frost will zap cold-sensitive crops, however even when the climate stays above freezing, crops will nonetheless expertise decreased development. And that’s all due to decreased gentle!
To assist make clear the significance of sunshine, let’s have a look at the instance of rising winter greens like spinach and kale in a protected construction like a excessive tunnel. Even when this tunnel is heated and stays above 50°, winter crops will expertise stagnant development. For those who plant kale seeds in December, they may develop solely an inch or so over the subsequent month. However in the event you plant these seeds in September, they’ll expertise a number of inches of latest development.
Whereas the hotter temperatures barely influence the distinction in development, gentle is the main issue! This is smart when you think about crops obtain about three hours extra gentle in mid-September than in mid-December.
Some folks assume this slowed development is unhealthy, nevertheless it’s a pure plant course of. Low gentle leads many perennial crops to expertise slowed photosynthesis and respiration, which results in decreased development. Chilly temperatures additionally restrict enzyme perform and kill above-ground plant tissue. These crops enter dormancy to outlive each low gentle and chilly temperatures after which regrow the next spring.
Planting Winter-Harvested Crops
Thankfully, you may develop many crops all through the winter. Chilly-tolerant veggies like spinach, kale, and carrots can survive frosts, and flowers like violets beautify porches and gardens even after the snow falls.
However although these crops are cold-tolerant, it doesn’t imply they’ll develop with little gentle! Like all crops, they gained’t expertise a lot development as soon as the sunshine drops under ten hours. And so they’ll expertise decreased development as gentle fades main as much as the primary ten-hour day.
A superb rule of thumb is to plant winter-harvested crops so that they’re 100% mature when the Persephone interval begins. Since they gained’t develop a lot afterward, you may depart them within the floor and harvest them all through the winter (assuming you shield them from the chilly).
Some crops that may maintain properly all through the winter embody carrots, kale, spinach, beets, parsnips, lettuce, and leeks. However keep in mind that these cold-tolerant crops are nonetheless vulnerable to wreck from frigid temperatures! For those who dwell in a chilly local weather, you could must use chilly frames, excessive tunnels, or row covers to guard the crops from damaging frosts.
Figuring out when to plant entails greater than wanting firstly of the interval and the times to maturity in your seed packet. Keep in mind, plant development will sluggish as daylight slows. So, when do you have to plant crops if you wish to harvest them in the course of the winter?
Let’s have a look at ‘Vivian’ romaine lettuce for instance.
The seed packet states that it takes 50 days for the lettuce to develop from a seedling right into a dense romaine head. Nonetheless, this quantity assumes that the lettuce is rising in full gentle. If the lettuce grows within the fading gentle of fall, you could account for slower plant development.
A superb rule of thumb is to extend the plant’s anticipated days to maturity by 40% within the fall. That implies that though ‘Vivian’ will take 50 days to mature in spring, it’ll take 70 days to mature once you plant it in fall.
With this info in thoughts, let’s decide after I would wish to plant ‘Vivian’ if I would like it to be mature for winter harvest. First, now we have to find out the beginning of the Persephone interval. As I discussed above, this happens on November 26 the place I dwell. Subsequent, we’ll depend again 70 days to achieve September 17. Which means I’ll wish to get my ‘Vivian’ transplants within the floor by September 17 if I would like them to mature by the point development stops.
Planting Overwintered Crops
If you wish to plant crops within the fall and harvest them the next spring, they don’t need to be totally mature by the point the Persephone interval begins. Though the crops will expertise stalled development throughout winter, they’ll resume development as soon as the winter solstice passes and days develop longer than ten hours.
Which means spring-harvested crops solely have to be 25-75% mature by the beginning of elevated darkness. When winter arrives, the extra mature the crops are, the sooner they’ll mature in spring.
Nonetheless, you must be aware that some crops are extra vulnerable to chilly injury in the event that they’re extra mature. For instance, garlic overwinters finest when the shoots are only some inches lengthy. If the crops have placed on a foot of development, chilly is extra prone to injury them.
Some crops that overwinter properly embody onions, garlic, carrots, lettuce, and arugula. Simply make certain to guard them from chilly temperatures and drying winds.
Succession Planting for Fall and Winter Harvests
Since decreased daylight slows plant development, succession planting in fall seems completely different than succession planting in summer season. If I wish to harvest radishes each week in late spring and summer season, I plant a brand new spherical of radish seeds every week.
But when I wish to harvest radishes every week in late fall, I’ll plant a brand new spherical of seeds each few days in mid-fall. Seeds planted two months earlier than the Persephone interval expertise noticeably completely different development charges even when planted a number of days aside.
Contemplate gentle and temperature in the event you’d wish to proceed rising all through the winter! Since plant development will stall as soon as days drop under ten hours, planting properly forward of the arrival of the Persephone interval will permit crops to mature in time for a winter harvest.