7 Benefits of Amending Your Soil in the Fall

Few plants are growing, leaves are falling, and temperatures are dropping. These fall conditions create the ideal environment for amending garden soil for a range of benefits. Improvements work while plants are dormant, creating fertile, porous dirt for their roots to grow into before spring. 

In autumn, you can mix in amendments without worrying about harming plant roots. You can apply thick layers of mulch without shading seedlings. It’s too cold for seedlings! It’s also too cold for most animals and insects that thrive in summertime.

Amend your garden to create habitat spaces for these creatures to survive freezing temperatures. Fall leaves, compost, and grass clippings provide valuable space for creatures like snakes, ladybugs, and bees to hide in. The cover keeps them safe from predators and warm despite recurring frosts. 

No matter your reason for amending your soil during autumn, you can confidently do so without fearing for your garden’s health. If any amendments don’t decay now, they will eventually as temperatures warm and snow thaws. There’s no harm in using mulch if you have it lying around!

Let’s discover how fall soil amendments can benefit your garden.

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Boost Soil Performance

Amending your soil means adding organic matter, fertilizer, or pH modifiers to create more inhabitable conditions for plant roots. Materials like compost add porosity to soils so they can drain freely and absorb water readily. The air pockets hold onto the water during droughts, and allow it to flow freely when there’s an excess.

As organic matter decays, it releases nutrients into the ground where shrubs and trees can access them. Soil microorganisms, worms, and beetle larvae eat debris and large particles. They process it, turning the waste into valuable humus. Humus is the black, crumbly end product of decay. Healthy garden soils have large amounts of this material!

Adding organic matter also builds structure underground. Twigs, leaves, and plant scraps create pathways for worms and creatures who create more pathways! They leave waste behind, and the waste helps regulate soil moisture. Organic improvements will help your garden grow more resilient to extreme weather, pests, and diseases. It’s incredibly helpful in breaking up clay or adding absorbency into excessively sandy areas. 

Amendments Decay Slowly

Low temperatures slow growth for many species; fungi, bacteria, archaea, worms, and insect larvae work slowly when chilly and quickly when warm. The ground insulates these creatures and keeps them alive, although they must retreat lower underground in some areas. Freezing ice threatens them if they stay on the soil’s surface.

One benefit of these low temperatures is the mulch you lay down will persist throughout the cold seasons. Add straw or leaves to your soil in summer, and they’ll quickly decay into tiny particles! Add layers of the stuff during the fall and it’ll insulate the ground until late spring or summer.

Slower decaying amendments mean there are persisting habitat spaces for critters that need them. Pockets between leaves, tunnels left by worms, and webs of overwintering spiders create cozy homes out of plant scraps, grass clippings, and fall leaves. As warm spring arrives, the materials quickly decay, animals come out of hiding, and plant roots suck up the nutrients they leave behind.

Ready Soil in Spring

Add improvements during the fall season and you won’t have to come spring! Your grounds will have the porosity, fertility, and structure they need for any plant to survive. Whether you’re growing annuals, perennials, or woody shrubs and trees, they’ll benefit from organic matter to boost their performance. 

In spring, you deal with young seedlings and tender roots—it’s hard to mix in things like compost or worm castings. Most annuals die by late fall, and perennials enter dormancy. You can safely mingle add-ons into the ground as deep as you’d like while the weather is cool. 

Dig amendments in four to six inches deep for best results. You may dig deeper if you deal with excessive clay or are starting with the French Intensive gardening method. Use a layer one to three inches thick and incorporate it evenly throughout the garden beds. It’ll bond with the native soil particles and create an ideal mix for future seedlings.

Adjust Soil pH Easily

pH modifiers need time before they start adjusting the levels. The more evenly you incorporate them, the better and quicker they work. Apply these amendments during fall to benefit your soil and bring the pH to your target range by spring. The slow-acting amendments have weeks to take effect while bulbs, shrubs, and trees are dormant.

Use garden sulfur or lime to adjust soil pH. Sulfur lowers the pH and makes soils more acidic, while lime raises the pH and makes them more alkaline. Easily mix in these amendments during autumn without worry about harming plant roots. Dig them six inches deep, and follow their packages’ instructions to find the correct dosage. 

Many acidic soil-loving shrubs like blueberries, rhododendrons, and hydrangeas appreciate a small dose of acidic fertilizer during the cool seasons. Use a soil testing kit to first see your soil’s pH so you can know whether you need to add sulfur or lime. Most vegetables and fruiting crops appreciate a neutral pH level near 7.0.

Help Local Animals

This is my favorite reason for adding amendments during fall—they help local wildlife! Provide homes, nutrients, and water for these creatures when they have dire needs. Worms, ladybugs, bees, and other beneficial insects rely on ground cover to survive extreme winters. Without it, they’re susceptible to the elements.

Overturn leaves during winter and you’re bound to find some critter hiding underneath. Wild animals crave the warmth the cover provides, and it hides them from hungry predators. Fireflies are one endangered species that need winter ground cover to survive. Place some leaves or straw on your beds and they’ll quickly move in.

Other more sensitive creatures, like snakes, also rely on soil amendments to survive. Beneficial garter snakes burrow underground as frost creeps in—add ground cover, and they’ll have more insulation above them. This keeps them closer to the soil surface where they can emerge to eat garden pests in spring. 

Boost Evergreen Plants’ Growth

Evergreen trees often get overlooked for care and maintenance because they’re green and always growing! They need nutrition, water, and air like other species, and autumn is a perfect time to feed them. Decorate their root zone with leaf mold, compost, or a similar carbon-rich amendment.

Woody trees and shrubs like laurels and boxwood use large amounts of carbon to create strong cells. Add carbon-rich soil amendments to their root zone and you’ll boost their growth the next season while insulating their roots. Warm roots are beneficial; they help the plant resume growing as days lengthen. 

These are some other evergreen species that appreciate fall soil amendments:

Aid Fungi, Bacteria, and Archaea

Three main organisms help add structure, fertility, and organic matter to existing soils. Bacteria, fungi, and archaea work in conjunction, creating better soils as they thrive. They each work differently and benefit certain plant species more than others. Choose which ones grow by controlling the amendments you use during the cool seasons.

Fungi thrive in carbon-rich soils where woody organic matter decays. They also, coincidentally, help woody trees and shrubs grow. Recycle nutrients by placing twigs and branches on the ground and letting them decay. Fungi will spread mycelia into the wood, break it down, and feed surrounding plants with the nutrients.

Bacteria help fleshy plants more so than woody ones. They’re beneficial for vegetables, fleshy perennials, and tender annuals. Bacteria thrive in nitrogen-rich amendments like compost, manure, or humus from fleshy plant scraps. Archaea help woody and tender plants. They’re present in rotting organic matter where fungi and bacteria are.

Best Amendments to Add in the Fall

Now that you know the benefits of amending soils during the fall, which amendments should you use? These are seven soil improvements for boosting your garden’s performance these cool months. 

Fall Leaves

Fall leaves are in ample supply during autumn and are perfect amendments to add to your garden! They’re ideal for helping wildlife survive the winter, as they mimic forest floor covers where leaves fall and stay. Avoid removing them once they fall, or rake them up and place them on your garden beds to unleash their beneficial properties.

Fall leaves help plants by releasing carbon and small amounts of nitrogen while they decay. They also aid fungi and mycorrhizae that grow root-like tendrils called mycelia between their folds. Give support to plants, animals, and microorganisms this season by leaving leaves in your yard.

Leaf Mold

Leaf mold is similar to fall leaves. Instead of waiting for them to decay, you speed up the process to make a quick and nutritious soil amendment. Place fall leaves in a pile, turn them regularly with a pitchfork, and keep them moist. In a few months, the leaves will crumble into a black, rich, and fertile material. Leaf mold is rich in carbon and ideal for woody perennials, trees, and shrubs. 

Compost

Compost is similar to leaf mold but uses other materials aside from leaves. It’s a mix of “brown” and “green” materials. Browns have more carbon than nitrogen, and greens have the opposite ratio. Add greens to browns in a ratio of 1:2 or 1:3, making a pile. Turn the pile regularly, keep it with 50% moisture, and watch as it turns into black, fertile soil. 

Biochar

Gardeners are learning the amazing qualities of biochar! It’s wood that you heat so it smolders without burning. The resulting charcoal is perfect for soils—it has air pockets that hold air, nutrients, and soil. The biochar provides nutrients as it decays, creating an ideal site for fungi or woody plants. Break it into small pieces and incorporate it throughout your beds, or dig in large chunks near woody trees and shrubs.

Straw

Straw, like fall leaves, provides beneficial carbon while also helping the soil structure. It’s from grass stalks that are dry and brown. Farmers use straw for animal bedding, although it’s also an ideal soil improvement to add during the fall. Place straw in one to three-inch thick layers on top of your garden beds, or scatter it throughout the yard alongside leaves, grass clippings, and biochar.

Worm Castings

Worm castings are little particles of black gold! They’re full of nutrition despite their unsightly source—castings are worm poop particles! Fear not, as they’re incredibly beneficial for plants. Worm castings improve water retention, drainage, nutrient availability, and they reduce pest and disease occurrences. 

pH Adjustors

pH adjustors like garden lime or sulfur are ideal amendments for adding in autumn. They work to raise or lower soil pH so that it’s in the range you’d like. Most plants prefer a neutral or slightly alkaline pH, although some species, like blueberries and azaleas, love acidic soils.