A Cozy Blanket for Your Garden: Choosing the Right Winter Mulch

Protect your soil throughout the cold season with the right option for your garden.

Winter mulch helps protect the soil from the season's harsh conditions. Afonkin_Y/Shutterstock

Winter mulch serves a slightly different purpose than summer mulch, which is used to conserve moisture and keep plant roots cool. Winter mulch is applied to help protect the soil from extreme cold, wide temperature variations (freeze to thaw), and the resulting frost heave (ice formation in the soil, which can push plant roots up out of the ground). Mulching also helps safeguard all-important topsoil from being eroded by rain and water runoff, keeps down weeds, and, if an organic mulch is used, improves the soil structure and reduces the need for fertilizer.

With a wide variety of organic and synthetic mulch options available, it’s important to consider price, appearance, function, and durability.

Application Advice

Winter mulches are typically applied after the first hard frost of the season—when the consistent cold weather has arrived, but before the plant roots have a chance to be damaged by extended freeze.

The exception to this rule is for annual vegetable crops, where the idea is to extend the harvest season. Mulch with two to three inches of organic mulch before the first frost. In more temperate areas, this might allow for survival and harvesting all winter.

For all other plants, the goal is to stop the ground from going through freeze/thaw cycles during winter. In these cases, applying mulch too early can smother the still-growing plant, cause heat to get trapped in the soil, worsen freeze/thaw effects, and encourage pests and disease. If the area, such as around a tree, is already mulched, pull it back from the trunk in early fall so the bark can properly harden for winter (cellular changes, including shrinking and dehydration, that help prevent freezing and damage to its living cells), then top up the mulch after the first frost. For perennial plants, wait until they have gone dormant. This is normally around the time surrounding annuals have died off.

Organic and Affordable

While there is no perfect mulch, understanding the unique characteristics, benefits, and drawbacks of each allows the gardener to choose the best mulch for each specific situation or the entire landscape. The easiest and cheapest option is to mimic a forest and use existing yard waste such as leaves, leaf mold, pine needles, and wood chips.

While whole leaves can work, they tend to blow away. Run the lawn mower over them or use a leaf mulcher or wood chipper. The latter requires an upfront cost but pays for itself over time, particularly if it’s used to make spring and summer mulch each year as well. Leaf mold, which is leaves that have already begun to decompose, most likely won’t need shredding. Pine needles are a great choice for acid-loving plants, and their interlocking nature makes them work well on a slope. Wood chips may be available free from the local municipality or can be made on-site from small branches run through a wood chipper/shredder. If there are no natural mulch sources on the property, it is readily available for several dollars for a huge bag at the local garden center.

All of the above should be applied in two- to three-inch layers, keeping it from direct contact with the plant. Also, wood chips take nitrogen from the soil as they decompose, which needs to be replaced by using a nitrogen fertilizer in the spring.

If one wants to use grass clippings, they need to be dried out first. Do this over several mowings and build up the layers slowly to keep them from compacting. Fresh clippings, in particular, will mat, prevent water from moving through, and can potentially smother the soil. Make sure the grass in question was not treated with an herbicide, such as weed and feed.

Natural mulch, such as pine needles and wood chips, is an easy, no-waste option. Mariana Serdynska/Shutterstock

Long-Lasting Solutions

Inorganic does not necessarily mean synthetic. Gravel, river rock, pebbles, marble chips, crushed stone, and volcanic rock are long-lasting, stay in place in high winds, keep weeds down, help prevent topsoil erosion, and, if applied thick enough, may help somewhat with freeze/thaw situations. They are best used in permanent planting areas such as foundation plantings, shrub beds, and more around the property. Often, they are underlaid with a weed block fabric (aka landscape fabric, Geotextile) to keep the small pieces from sinking into the soil beneath, which does its part to help reduce temperature fluctuations. Be sure to keep limestone gravel away from acid-loving plants as it raises the pH of the soil. Always keep stones away from the plant’s trunk or stem, particularly in summer when they will get hot.

Likewise, rubber mulch made from ground-up tires and artificial (plastic) pine needles are two other relatively new options that don’t decompose and therefore never need to be replaced unless scattered by feet, a lawn mower, or a weed trimmer. Like their rock counterparts, they are typically installed over a weed block fabric, which provides a blanketing effect, and the combination can help mitigate soil temperature fluctuations.

The only thing left to consider is what type of blanket to cuddle up in while enjoying a hot chocolate in front of the fire.

Inorganic options such as gravel, river rock, and pebbles are longer-lasting. Bespaliy/Shutterstock

The Veggie Garden

The right covering will get next spring’s garden off to its best start ever. Two are free, and the third is reusable.

Love Those Leaves

Put the vegetable garden to bed under a three- to four-inch layer of leaves to prevent soil erosion, put lost nutrients back into the soil as they decompose, suppress weeds, and provide a home for beneficial organisms. Shredded leaves break down faster.

Weeds Begone

The use of polyethylene has become so common in the garden that the USDA has given it a name—plasticulture. Covering the garden with polyethylene film (aka plastic sheeting) or landscape fabric will smother weeds, protect topsoil, and may help it warm up faster in the spring.

Common Cardboard

To achieve similar results to the more expensive polyethylene sheeting or landscape fabric, lay delivery box cardboard down in overlapping sheets and spray it down with water so it stays in place.