Winter gardening is a slower, more careful affair than the verdant bustle of summer’s lush, rapid growth. However, the joys of opening a cold frame or looking under the Frost Cloth to see bright, vibrant green when most other colors have faded into Winter dreariness are reason enough to accept the challenge. And many garden staples like leafy greens, broccoli, or carrots taste sweeter after some cold weather.
There are a few unique considerations for transitioning a bed from summer to winter growing, but the basics of plant needs–fertile soil, light, moisture–are the same.
My winters are too cold, you might think. I can’t do that here. However, most people in the US can grow at least part of the winter, even without supplemental heating. And you can do it without a large, expensive greenhouse.
In mild climates, extra mulch and a floating row cover may be all you need to continue gardening throughout winter. Areas that don’t receive temps below about 25 degrees Fahrenheit can often grow winter hardy plants right through the cold season.
How To Start a Winter Vegetable Garden
One of the keys to winter gardening is to start before the deep cold sets in. Light and temperature are two of the most significant limiting factors for photosynthesis. Lower light levels and cooler temps mean growth will be slower than in warm summer weather.
Due to shorter daylight hours, the light available to your winter plants is less than they would have enjoyed in the summer. In many areas like the PNW, typically cloudy weather in winter exacerbates the problem. If you’ll be permanently covering your winter veggies to provide protection from the cold, how much light gets through the covering is essential. After all, without light, your plants won’t grow, or even survive. Look for 80-90% light transmission levels in frost cloth or plastic coverings.
Temperature is what most of us think about when considering winter vegetable growing. How can we make it warmer? Even cold-hardy plants stop conducting photosynthesis at about 32°F, and anything colder than 50°F usually significantly slows plant growth. To retain a little extra warmth, several methods are available at low cost for DIY winter gardeners.
Cold Frames, Low Poly Tunnels, and Floating Row Covers
Cold frames and low poly tunnels are the ticket for gardeners in chillier locations. A cold frame can be made of many recycled materials and is surprisingly effective. This technique has been used for centuries.
One of my favorite ways to DIY a cold frame is by stacking straw bales to form a square shelter with grow space inside and topped with an old storm window. Two bales long and one bale wide make a nice manageable size. Make sure to place it in a sunny spot out of the wind. Stuff extra straw into any cracks to keep out cold drafts. Cold frames work best for in-ground gardening, as the soil will warm during the day and hold some heat at night.
Low polytunnels can be made quite affordably from PVC frames and greenhouse poly covering. Don’t purchase clear plastic made for use as drop cloths or other uses, as it typically won’t last well under the UV light of the sun or freezing temps. Look for greenhouse-specific poly, in 6 mil thickness. Many online vendors sell it by the foot in standard widths.
PVC pipes and covering for a low poly tunnel four feet wide and 25 feet long can be sourced for under $100. And, the materials can be reused for many seasons. My low polytunnel will often reach 70 degrees or warmer inside on sunny days, even on a chilly 30-degree day. They’ll cool off again at night, but the temperature boost is enough to allow photosynthesis.
Pro tip: buy the PVC pipes for use as hoops at a local home improvement store to save on shipping odd-sized items. While many folks use ¾” PVC, I find the 1” diameter stuff much sturdier and able to handle light snow loads and wind better, albeit it’s harder to bend.
Floating row covers are great for extending the season in spring or fall, and for mild climates, may be all you need. Use floating row covers with frost cloth for overnight protection when the temps drop, and remove them or roll them back on warm, sunny days. They typically have high light transmission levels if used only one layer thick, so you can leave them on for several days at a time if needed.
Frost cloth row covers will provide about 4°F protection. Plants that only tolerate about 30°F will likely survive a 26-degree night. Make sure to anchor frost cloth to the ground with rocks, bricks, or other materials. Cold drafts sneaking underneath will negate the benefit of any heat retained.
The Best Winter Veggies To Grow
Suitable vegetables to grow in winter are those described as cold-hardy. Most leafy greens like kale, spinach, mustard, collards, and lettuce do well in colder temperatures. Other vegetables include broccoli, bok choy, carrots, and radishes.
It probably won’t do well even in a cold frame if it needs to flower and fruit, like a tomato. You’ll need a fully heated greenhouse to enjoy garden-fresh tomatoes in February.
What Veggies Are Harvested in the Winter
Some crops are grown in summer and fall but can continue to be harvested in winter, especially if you have a mild climate. Brussels sprouts, kale, and greens come to mind. These plants may already be established in your garden from summertime and can be nurtured and protected with the above methods for continued winter harvests.
Other crops like carrots, potatoes, salsify, parsnips, turnips, and similar root veggies can be left in the ground for storage and dug as needed if your ground doesn’t freeze hard. Remember, raised beds will commonly freeze harder than in-ground soil and earlier.
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