Find out why your garden needs mulch and how it will improve your soil to give plants a better growing environment. There are plenty of organic options right in your own yard including fallen leaves.
For more budget-friendly ideas, use these tips to make use of leaves instead of sending them away.
What Is Mulch?
Mulch! Mulch! Mulch! It’s mentioned all the time in gardening but what is it and what does it do?
Mulch is anything you apply in a layer on top of your soil. It may be there naturally like fallen leaves or it could be placed there intentionally liked shredded wood chips to help improve and protect the soil.
The mulch you choose and the best way to apply it depends on what function you want it to serve. I’ve provided lots of tips and examples below.
While you can grow plants without mulching, when you look at the health of a garden and its soil over the years, mulch becomes an integral part of maintaining that health. And this is why you hear experienced gardeners going on and on about it: it’s a valuable resource.
I first became an avid mulch fan years ago after reading garden advice from Ruth Stout. Not only was Ruth a no-dig garden pioneer but she was also, arguably, the Queen of Mulch, always dressing her soil in a thick layer of organic mulch year-round for a robust, productive vegetable garden.
- 4 Types of Mulch
- Advantages to Using Organic Mulch
- Choosing The Right Mulch
- How Much Mulch Do I Need?
- Tips For Applying Mulch
4 Types of Mulch
Mulch comes from various sources. Here are the basic groups.
Natural Organic Mulch
Here the word organic means it is made of (formerly or currently) living plants or plant parts.
In general, organic mulches biodegrade fairly rapidly, although some—like wood chips—can take longer.
- Nut husks
- Pine needles
- Tree bark (chunks or shredded)
- Wood chips
Some organic mulches are sold in different colors (red, brown, black). Check with your seller to learn what they use to achieve the colors—unlike years ago, many today use harmless vegetable-based dyes.
Mulch From Processed Natural Materials
These breakdown at a moderate rate.
Natural Inorganic Mulches
This includes items like rubber or plastic chips or sheeting, and landscaping fabric.
Items like plastic sheeting used as mulch can have valuable, temporary uses including the eradication of pernicious weeds but are not recommended long-term for growing plants.
The mulches we’re interested in for home gardens—specifically to enhance the soil—are the ones from organic sources that biodegrade and benefit the soil.
Starting a new garden bed? Use this cardboard method to speed up the process.
Advantages To Using Organic Mulches
Mulch is not just for garden beds. Consider adding it to container plants to gain the same advantages.
Here are some reasons why mulch is so useful.
- Organic Matter & Nutrients
It depends on what you use, but, in general, as organic mulches decompose, they add organic matter and nutrients to the soil with the help of microorganisms and worms.
This means, in addition to all the advantages listed below, organic mulch can also be considered a natural, (very) slow-release fertilizer.
- Weed Suppression
Mulch can really slow down weed seeds but the caveat is—it’s not selective. A thick layer of mulch is going to cut off light to any seeds in the soil, not just weeds. For this reason, we mulch around—but not overtop— the seeds and plants we want.
Established weeds are mightier than the mulch and should be removed before applying mulch to your beds.
- Moisture Retention
When the sun beats down on bare soil or the wind blows across it, water in the soil evaporates. A layer of mulch shields the soil below, helping retain moisture. This means less time spent watering and better water conservation.
- Soil Temperature Moderation
Plant roots do not fare well in hot temperatures. A layer of mulch protects soil from the sun’s rays, keeping the soil cooler on hot days and better insulated on cooler days. By taking the edge off these extremes, plants—especially ones that don’t have deep roots yet—are better protected while they grow.
- Reduce Soil Erosion
Both water and wind can carry our soil away—and take nutrients with them. Mulch can slow or stop this. Or take the hit instead.
- Prevent Soil Compaction
While mulch can’t change existing compacted soil, it can help prevent it. Think of it like a cushion that softens the impact of our feet on the ground below.
- Divert Organic Materials From Landfill
The decades-old habit of “tidying” our gardens and sending leaves and other organic materials away has not served us well.
And how silly are we to dispose of these things in fall only to buy an equivalent product in spring?
If you’ve got leaves, branches, or a tree that had to come down—make use of what you can. One tree can become a lovely pile of mulch!
One drawback to mulch is, because it decomposes, it does need to be replenished each year. Depending on what you use and the size of your garden, this could add a significant cost to your annual garden budget. I find it so beneficial to the garden that I choose it over other purchases—even plants!
Choosing The Right Mulch
The best mulch option for your garden is going to depend on several things: the purpose, what’s available, and your budget.
Local landscaping suppliers often have a few options to choose from.
You also don’t have to stick with one type: it’s fine to combine several mulches together. In my garden I use shredded wood chips, compost, and fall leaves or leaf mold.
Be sure to see the mulch in-person before placing your order. Watch for unwanted things like shredded plastic, foreign objects, sticks, or garbage.
I prefer purchasing from a landscape business that uses the same mulch I’m buying for their (expensive) clients and worries as much about unwanted fill and weed seeds as I do.
Avoid the lure of landscaping fabric—which is sometimes applied under mulch. It’s a short-term weed-suppressor that ends up creating a big mess. Weeds eventually grow through it and you end up with a lot of non-biodegradable garbage.
Here are some tips for refining your choice of mulch.
Mulch for Flower and Vegetable Beds
If you want to improve the soil in your flower and vegetable beds, look for an organic mulch that is fairly finely shredded and allows water and air to reach the soil below. We want something that decomposes fairly rapidly.
Avoid things like chunky pieces of tree bark or larger hardwood chips that are slower to decompose and form a restrictive barrier.
Mulch for Trees and Shrubs
While you also need water and air to reach the soil and roots of trees and shrubs, sometimes a coarser mulch that is a bit slower to decompose works nicely so long as it is not applied too deeply.
Finer mulches also work but you may save some time and money by choosing something that takes longer to breakdown.
Mulch for Paths & Walkways
Here the emphasis is on function and appearance, not necessarily enhancing the soil.
The first decision is whether you want a softscape or hardscape.
Organic mulches like finely-shredded wood chips can create a cushioned, comfortable walkway for kids and pets.
Inorganic mulches like stones may be more aesthetically-pleasing although weeding may be more cumbersome when they eventually appear.
Just be sure that rain water has somewhere to go.
How Much Mulch Do I Need?
In general, it is recommended to apply mulch approximately 3-inches deep for flower and vegetables beds and around trees or shrubs.
Assuming the mulch is shredded and not smothering the soil below, this depth offers a good amount of protection from the sun and wind while still giving the plants what they need.
As the months go by, you will notice your mulch gradually decomposes. I try to top mine up an inch at a time to maintain the desired depth.
Mulch Calculation Tool
Use our handy online soil calculator tool here. It works for mulch, compost, soil, and potting mix. You can calculate the volume needed for garden beds, raised beds, window boxes, and flower pots.
Sample Mulch Calculation
1 cubic yard of mulch covers approximately
100 square feet when applied 3-inches deep
Truck deliveries of mulch are often sold by the “yard.”
On cubic yard is 27 cubic feet (3-feet x 3-feet x 3-feet) and covers approximately 100 square feet (with a bit to spare) when the mulch is applied at 3-inches deep.
The math actually works out to 25 cubic feet but we round up to allow for uneven application.
A good mulch supplier will help you calculate the amount needed.
Check the product bag: it should list the contents by weight and volume. The volume should be listed in cubic feet (or the metric equivalent). There may even be a chart showing coverage at various depths.
You need 25 cubic feet to cover 100 square feet at 3-inches deep.
Knowing this formula, you can determine how many cubic feet you need for your garden.
There are also lots of mulch calculators online.
Garden Bed Size Examples
- 10 x 10-feet garden bed = 100 square feet
- 4 x 4-feet garden bed = 16 square feet
- 4 x 8 -feet garden bed = 32 square feet
- 3 x 12-feet garden bed = 36 square feet
- 3 x 25-feet garden bed = 75 square feet
Tips For Applying Mulch
More Is Not More
If mulch is too thick or dense, air and water cannot reach the soil below.
- Use organic mulches from natural sources (not synthetics).
- Remove weeds before adding mulch to your garden beds or containers.
- For growing flowers, vegetables, trees, and shrubs, choose a finer mulch that allows water and air to reach the soil below and apply it approximately 3-inches deep (not more).
- Do not mulch overtop seeds or seedlings (unless they are weed/unwanted).
- Avoid applying mulch against stems or trunks (no mulch volcanoes!) by leaving a few inches of space around them.
ListenNEW! Click play to listen:
When mulch is piled up against the trunk of a tree, it’s called a mulch volcano. While still a fairly common practice, particularly with landscaping services, it is commonly frowned upon within horticultural communities.
Potential problems include lack of air circulation at the base of the tree, blocking tree root access to water, encouraging unnatural root growth within the mulch, fungal and bacterial growth on tree bark, and rodent damage. Plus, it just looks odd.
This said, there is little research about the potential harm of mulch volcanoes, so, while we suspect they are not good for trees, we do not have studies to confirm this.
Garden Soil Tips
Soil | The upper layer of earth in which plants grow, a black or dark brown material typically consisting of a mixture of organic remains, clay, and rock particles.
Mulch | Placed on soil, organic mulch can protect soil, retain moisture, and gradually fertilize the garden.
Leaves | Finely chopped fall leaves make excellent mulch.
Leaf Mold | Decomposed fall leaves beneficial to soil structure.
Compost | Decomposed organic matter providing nutrients for the garden.
Potting Mix | Contains no soil: designed to optimize plant growth in pots.
Seed Starting Mix | A lightweight potting mix for sowing seeds in containers.
Soil pH | Knowing your level (which may vary) is informational, not a call to action. Most soils fall in the range of 5 to 8 and accommodate a wide range of plants.
Free Soil Calculator Tool | Estimate how much you need and what it will cost
Along with mulching garden beds, this lists more garden jobs for a sunny autumn day.
~Melissa the Empress of Dirt ♛
Seed Starting for Beginners
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by Melissa J. Will
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