Why Mulching In The Fall Is Essential For Stronger, Healthier Plants In The Spring

As fall approaches, you may feel like it's time to hang up the gardening hat and take a break until spring returns. However, by mulching in the fall, you can knock out one of the biggest gardening tasks and make the following growing season even easier. Between starting seeds, preparing the soil, and other early-season preparations, laying down mulch before winter can be a huge time and energy saver. More importantly, however, are the benefits mulch brings to the garden once the temperatures drop.

There are several types of mulch to choose from, including organic, synthetic, and even living mulch. Organic mulches, like pine needles, straw, leaves, and wood chips, are made up of natural materials that will decompose and break down over time. Inorganic or synthetic mulches include stones, rubber, and landscape fabric. Ground covers are often referred to as living mulch, which are low-growing plants that create dense mats. Each type has its pros and cons, so choosing the best type of mulch for your garden comes down to what you want to use it for and where you plan on using it.

Although you'll see most of the growth in warmer months, many weeds' life cycles start much sooner, before you even see the plant. Species like henbit (Lamium amplexicaule) and purple deadnettle (Lamium purpureum) have seeds that will germinate in the fall. They'll start sending out roots underground, and by the time they emerge, they will have already taken nutrients from the soil. If you live in an area with mild winters, by spring, your plants will face tougher competition, and these weeds will be much harder to eliminate once they're established. Covering the soil with mulch in the fall creates a barrier that prevents some seeds from germinating, while blocking sunlight and smothering any that do sprout.

Remove any existing weeds before mulching in the fall. You can use organic or inorganic mulch, though you'll want to make sure any organic mulch is free of new weed seeds. Otherwise, you risk aiding the spread of weeds, which defeats the purpose of trying to prevent them in the first place. Grass clippings can make a great natural mulch, but avoid any that have been treated with broadleaf herbicides, which can affect some crops. For most mulches, you'll only want to apply a layer that's 3 inches or less. Over-mulching can restrict the oxygen that plant roots need to grow. For grass clippings, you'll need to further decrease the depth (or mix with another material like dead leaves), as they can pack down and create an impermeable mat. 

Unfortunately, it's not just our skin that gets dry once winter hits. Between weather fluctuations and dry winds, the soil can become extremely dry as the temperatures drop. Although plants go dormant in winter, their roots are still alive and require some water to absorb and store nutrients for spring growth. Additionally, water holds on to heat during the day, then gradually releases it overnight. Because of this, dry soils can freeze more quickly, and frost can penetrate even deeper into the ground, putting plant roots at greater risk of cold damage.

Applying a layer of mulch is one of the best ways to insulate the soil and keep water from evaporating as quickly. But first, give your plants a good watering before laying down mulch. Organic mulches, particularly coarse materials like wood chips or shredded wood, excel at conserving moisture. Avoid fine-textured or waxy mulch and mulching fabrics, as they can actually repel water and prevent it from seeping into the soil. Apply an even, 2- to 3-inch layer that covers the root zone around any overwintering plants. Although mulch aids in moisture retention, you'll likely need to provide supplemental water from time to time.

Healthy roots are necessary for plants to survive the winter, so it's important to do what we can to protect them as much as possible. Even if the plant seems fine above the soil, frozen ground around the roots can be extremely damaging, and the plant may not survive if the ground freezes repeatedly. Additionally, winter weather isn't steady, and premature freeze-thaw cycles can put stress on a plant's roots. Without a protective barrier, the cold air can penetrate deeply into the soil, putting shallow-rooted and young plants without established root systems at extra risk.

Cold-sensitive plants, newly planted perennials, broadleaf evergreens, and plants with shallow roots are much more likely to survive the winter if you apply mulch in the fall. Mulch acts as a natural blanket that locks in heat while insulating the soil. This helps to prevent root damage from frozen soil and plant stress from extreme temperature fluctuations. Chunky, organic mulches or straw work best, as they have air pockets that help create better insulation. Ideally, wait until after a frost or two to let the soil cool and give your plants time to develop cold hardiness.

Fluctuating winter temperatures don't just put the roots at risk beneath the soil; they can also cause other issues for plants. When the soil is repeatedly subjected to cycles of freezing and thawing, it naturally expands and contracts. This constant movement can break off plant roots and push the entire plant up and out of the soil. Exposed roots are then subjected to cold weather and dry winds, which can cause damage, stunted growth, or even plant death. Plants with shallow roots don't have the expansive root systems to lock them deep into the ground, making them most at risk.

Because mulch insulates the soil and prevents rapid temperature swings, it can help keep the soil from expanding and contracting. Apply an even layer of mulch after a few hard frosts have occurred, and be careful not to bury the plant's crown. Even with a flawless application, you'll want to check on your perennials throughout the winter. Mulch can conceal any lifted crowns, so without monitoring, you may not notice until it's too late. If you do see a heaved crown, either gently press it back into place or cover the exposed roots with fresh soil. Then, top the area with mulch.

Organic mulch will naturally decompose over time and eventually will need to be reapplied, but this isn't necessarily a bad thing. As leaves, twigs, pine needles, and other plant materials fall to the ground, they naturally decompose and release nutrients back into the soil. Soil that's rich in organic matter has improved structure, and does a better job of holding onto potassium, magnesium, calcium, iron, and other nutrients that plants need to grow. Applying mulch in the fall gives it several months to break down, meaning more organic matter for your plants once spring arrives.

There are several eco-friendly mulch options, and most gardeners can find them for free right in their backyards. Fallen leaves, pine needles, and grass clippings can all work, so long as they're free of chemicals. If using grass clippings, it helps to combine them with another type of mulch to create some air pockets. On its own, the grass can pack down into a thick mat that blocks water and oxygen from reaching the soil. You can also purchase organic mulch like shredded bark, wood chips, straw, or cocoa hulls. When using wood chips, it's better to opt for aged wood chips, as they cause less nitrogen depletion than fresh chips. Once it's time for new mulch, work what's left into the soil so it can continue releasing nutrients.

One plant many homeowners mightn't think to mulch is grass, but mulching the lawn is a great way to save money on fertilizer. Both grass clippings and fallen leaves contain nutrients, and when left on the ground, they enrich the soil and make your turf even healthier. Additionally, organic mulch can create a barrier over bare spots, making it more challenging for weed seeds to germinate.

When mowing your grass in early fall, leave the clippings behind to feed your lawn nitrogen, phosphorus, potassium, and other nutrients. To ensure even distribution, either use a mulching mower, retrofit your existing mower with a mulching blade, or spread out any clumps with a rake so they don't smother the turf. As the season progresses and leaves begin to fall, you can apply the same approach. Set the mower to its maximum height and cut the grass in one direction, then do a second pass from the other angle to make a criss-cross pattern. Repeat every week or so, depending on how many leaves drop. The idea is to lightly topdress the lawn with shredded leaves, not to cover it thickly. If you wind up with a dense layer of leaf mulch, gather the excess to use in other areas of your yard, like around bushes or in garden beds. The main drawback of mulching fallen leaves is the difficulty of mowing when they're wet, so aim to mow once they're dry. 

Besides mulch mowing leaves, you can also gather some up to use as mulch in your garden beds. Although a leaf pile may not look like much, it's actually a valuable habitat to many overwintering insects and animals like fireflies, bees, birds, and frogs. Many of these creatures are some of the best garden helpers, so you'll want to keep them around. Pollinators are necessary for most crops to produce, while other wildlife feeds on pests that may plague your plants come spring.

When you mulch with fallen leaves, you provide your small backyard inhabitants a place to stay hidden and warm, while naturally feeding your soil at the same time. Leaf mulch offers the same benefits as other mulches, like regulating soil temperatures and retaining moisture. Once you've gathered the fallen leaves, place them in your garden beds, around trees or shrubs, or anywhere else in your yard that needs mulching. Make sure not to apply a thick layer, as it can either create a mat that blocks water and oxygen or lock too much moisture in the soil. Shredding the leaves beforehand can also help them break down faster and create a more even mulch layer.

If you looked at your soil under a microscope, you may be surprised to see how lively it actually is. Just one teaspoon of soil can contain millions of beneficial bacteria, which break down organic matter into nutrients your plants need to grow strong. During winter, lower temperatures, less moisture, and fewer nutrients cause microbial activity to slow down. By mulching with organic matter, you'll provide these organisms with food and moisture, allowing them to remain slightly more active throughout the colder months. Your reward? Nutrient-rich soil for your spring plants.

Not all organic mulches are created equal, so if your goal is to have healthy spring soil, opt for materials that will steadily break down. Shredded leaves, grass clippings, and pine needles gathered from the yard are all great food sources for microbes. You can also use wood materials like bark or wood chips, but make sure to choose an undyed type. Dyed mulches often contain colorants and contaminants that can leach into the soil. 

Bare soil is vulnerable to erosion in fall and winter, so it's important to take precautions before the weather cools down. When rain hits the soil, it loosens the surface particles and, on slopes, can wash them away. Over time, this depletes the topsoil and leaves behind hard, compact dirt where plants struggle to grow. During winter, snow can accumulate on top of the frozen ground, and once temperatures rise, quickly melt and create a surge of water, which rushes over and loosens the soil. As gravity pulls the water downslope, the melted snow will carry the small particles and nutrients along with it.

Mulch provides a shield over your soil, reducing the impact of raindrops and slowing the flow of water. Loose, organic mulches, like straw or wood chips, are a great option, though they may need to be anchored down with netting or other materials to keep them from blowing away during heavy winds. Another option is living mulch, or ground covers that prevent soil erosion by anchoring the soil in place. Some ground cover plants can remain attractive year-round, and many varieties produce stunning, pollinator-friendly flowers during the growing season. 

A fresh blanket of snow can beautifully decorate the winter landscape, but heavy snowfalls can put a lot of weight on your soil. If a mound of snow sits on top of the ground for long periods of time, it compresses the particles, eventually leading to compaction. Once spring arrives, dense, compacted soil won't be able to properly drain water, which can lead to issues like root rot. And with the particles pressed together, there's little space for necessary air and water to reach plant roots.

A layer of organic mulch prevents compaction in two main ways. First, it absorbs and distributes the weight over a larger area, creating a buffer that keeps the soil particles from compacting. Then, as the natural materials break down, they release organic matter into the soil that improves the structure and helps to reduce soil compaction. For garden beds, trees, and shrubs, choose a woody organic mulch like shredded bark or wood chips.

You can't always avoid plant diseases, but there are ways to keep them from spreading. Many disease-causing pathogens live in the soil, and upward splashes from watering or rainfall can cause them to make contact with nearby leaves, infecting your plants. Some weeds and their seeds also host these pathogens, which may germinate in the fall and lie dormant in the winter, ready to spread disease when they emerge in the spring. By applying mulch in the fall, you'll create a protective splash barrier before rainy weather hits while also suppressing potentially disease-spreading weeds.

While mulch works well to prevent the spread of plant diseases, improper application can actually contribute to their spread. If disease is an issue in your garden, avoid using any affected plant materials to create mulch, such as tree branches, without properly treating them first. Avoid applying mulch too early when the soil is still warm, as this can promote fungal diseases. Once the temperatures dip below freezing, you can apply 2 to 4 inches of organic mulch. One common mulching mistake is layering it too close to the base of shrubs, tree trunks, or plant crowns. If piled onto the plant, the mulch can hold onto moisture and create an environment where fungal disease or crown rot can thrive. 

There are several reasons you should be mulching around your trees and shrubs, and fall may be the perfect time to get the job done. Not only will it help protect overwintering roots, but creating mulch rings can protect your larger plants from competition with grass for moisture and nutrients. Mulching in fall keeps grass from slowly taking over the area around trees and shrubs, preventing it from stealing resources once growth picks up in spring. Without this barrier, you'll likely need to mow or trim right up against the trunk in spring, which can cause accidental damage from lawnmowers or weed whackers.

Try to create a mulch ring that matches the size of the canopy to ensure you're covering the entire root zone. As the shrub or tree grows, you'll need to continue expanding outward to provide adequate coverage. Make sure not to be too heavy-handed, as a mulch layer that's thicker than about 3 inches can block oxygen and water from penetrating through, and, conversely, trap too much moisture in the ground. When making the ring, start about 3 inches away from the trunk. This prevents moisture from building up against the bark, which can lead to rot, fungal growth, and pest infestations.

Nobody wants to tiptoe to their car, hoping that the ice on the walkways isn't too slick. Deicers are great for quickly melting frozen water, but they can also be detrimental to landscape plants. One of the most surprising ways to use mulch in your yard and garden is as a buffer against these treatments. Although most plants can tolerate low concentrations of salt, high sodium content from road deicing salt can disrupt the nutrient balance and damage the roots and foliage or even kill plants. By putting mulch down in the fall, you create a barrier before icy weather hits and block some of the deicers from seeping into the soil.

Even if you don't use deicers around your property, melted snow from nearby treated streets or sidewalks can travel to your yard and seep into your soil. To keep your plants safe during an icy winter, apply a layer of mulch around the roots of landscape plants, especially if they're near any roads or walkways. Certain trees and shrubs are especially sensitive to salt damage, including trees like larches, oaks, maples, and redbuds. Evergreens like false cypress, balsam fir, hemlock, and yew are also at high risk because their foliage remains through winter and can be burned by salt spray. Popular landscape shrubs, including burning bush, dogwood, rhododendrons, and azaleas, can also suffer when exposed to high sodium levels.