Homeowner’s Guide To Garden Soil Treatment for the Winter

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In winter, your garden can still be working, creating rich beds for spring planting. From compost to cover crops, here are some soil treatment ideas.

The season’s final tomatoes and arugula disappeared into last night’s salad. The sunflowers are all wilted. The squirrels are in hyper-gear preparing their stashes. And the air has that first hint of winter. Now what?

Now it’s time to make your next spring’s self happy with your fall self by treating your soil for the winter. It might sound like a hassle, but it’s not terribly complicated. All you need is a winter soil treatment like compost, mulch or even weeds.

Once soil temperatures drop below 45 F, soil organisms slow down and hibernate through winter. You can use a soil thermometer to measure soil temperature. Good, treated soil protects roots and those hibernating insects and microbes from freezing when temperatures drop.

“Living soil has the same four basic requirements that wildlife and people do: food, water, shelter and air,” says Mary Phillips, head of Garden For Wildlife. “And without those, it starts to die. But winter is ever-changing and you can still improve soil.”

What is Soil Treatment?

Soil treatment remediates or fixes soil by adding nutrients and organisms to make it more viable for plants to live. It can also rid soil of harmful chemicals, or amend it if it’s too acidic or has too much clay, sand or rocks.

“While some gardeners may have perfect soil, for the most part, suburban soil is less than perfect,” says Phillips. “Turning poor soil into plant-friendly soil is not difficult, once you understand the components of healthy soil.”

Soil Treatment Methods

To keep your soil healthy over winter, don’t till it or break it up. That’s better left for early spring. Doing so before the winter disrupts healthy soil structure and biodiversity.

“At the end of a growing season, garden soil may feel loose,” Phillips says. “That is due to the chains of roots and mycelium running through it. These microscopic threads will slowly rot through winter, along with roots left behind by veggies and weeds, creating healthy, organic matter for spring.”

Here are some other ways to keep your soil and its inhabitants happy and snug over the winter.

Add Compost

Compost can be piled on uncultivated garden beds that would otherwise remain bare until spring. These beds can then be covered with a low row cover or old blanket. Compost enriches and binds soil, allowing air and water to move through. Organic matter also retains moisture so it can absorb and store nutrients.

“Amend, amend, amend,” says Phillips. “Most importantly, organic matter is food for microorganisms and other forms of soil life. The cover helps to regulate heat, moisture and cushion the bed, reducing compaction caused by snow and rain.”

Mulch

Over winter, mulch retains moisture and protect soil and roots. “Mulching materials, such as leaves, are free for the raking, and they do a great job of protecting soil from the ravages of winter,” says Phillips. Wood chips or straw work fine, too.

Grow Crops

Try planting native, non-invasive cover crops, like local species of goldenrod, wild rye, common yarrow, vetch and peas. These support beneficial insects, provide cover, prevent erosion and return nitrogen and other nutrients to the soil. Because they are adapted to your local climate, they require little to no irrigation and maintenance.

“Cover crops also act as a living mulch to shelter soils and control weeds in the off-season,” says Phillips.

In spring, chop over-wintered cover crops directly into spring soils a few weeks before planting.

Tolerate Winter Weeds

Weeds protect soil and provide cover and food for wildlife. With their long, thin taproots, dandelions, bittercress and other winter weeds penetrate down into the soil, which improves soil drainage.

“Weeds that grow in summer tend to be large, aggressive plants that quickly take over any planting, but winter weeds are different,” says Phillips. “There is seldom a crop present for them to smother, and common weeds like henbit and chickweed often form green mats of foliage that protect the soil from erosion.”

To keep winter weeds from reseeding too heavily, hoe them down in early spring and compost them.

Test Your Soil

Soil tests are a great way to find out what your soil needs and what is present in it. For best results, take nutrient tests in the late summer or early fall.

Which Soil Treatment Is Best for Winter?

Whichever ones you can get around to implementing before the snow flies. The more you do, the more your garden will flourish come spring and summer.

When To Apply Soil Treatments?

Most of these treatments are best to do before your soil freezes. Sow seeds of cover crops and add compost so it has time to start the breakdown period. You can mulch anytime, but the earlier the better, as it keeps soil warmer and protected longer.  That encourages soil microbes, worms and other organisms to stay awake later.

Karuna Eberl
Karuna writes about wildlife, nature, history and travel for magazines, newspapers and websites including National Geographic, National Parks, Discovery Channel, Atlas Obscura and the High Country News. She's also produced a number of independent films and directed the documentary The Guerrero Project, about the search for a sunken slave ship. She and her husband, Steve, wrote an award-winning guidebook to the Florida Keys and are currently completely renovating an abandoned house in a ghost town. She holds a B.A. in journalism and geology from the University of Montana. Member of OWAA, SATW.