How to Mulch: A Gardening Guide

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Have you ever wondered exactly how to mulch or what are the best practices? Today, we’ll answer all your questions.

Mulch is any material that is laid on bare soil. It can be organic (like wood chips) or inorganic (like stones) and can be used for many purposes.  Gardeners use it to suppress weeds, regulate soil temperatures, to protect against equipment damage, and as a pleasing aesthetic. 

Knowing how to do it properly is important – if improperly applied, it can cause problems.

Mulching is not a magical solution and isn’t always necessary.  Sometimes, our plants will grow better without it.  However, there are times when a 2 to 4-inch layer in our landscapes is beneficial. 

For instance:

  • Wood chips circling a tree create a buffer that prevents damage from lawn mowers and string trimmers.
  • Grass clippings or straw applied between the rows of a vegetable garden keeps weeds down and provides a walking/maintenance path.
  • A light layer of leaf mold around newly planted shrubs or perennials will help moderate soil temperatures and hold in moisture.  This allows the plants to establish themselves better.
  • Winter covers protect tender perennials and help prevent frost heave.
  • Organic mulches break down over time, conditioning the soil and adding nutrients.
  • A bed of stones or decorative rock can be installed in a spot where nothing grows, such as under a deep eave.
  • Rubber nuggets under play equipment make a softer landing spot for children.

Keep reading to learn how to do it properly.

Mulching does not have to be difficult. Learn the process with this step by step guide

What You’ll Need

  • Mulch!  See our article on the benefits of different types of mulch to determine the best product for your garden.  Buy from a reputable dealer.  Trash, weed seeds, and toxins can be present in inferior products.
  • Garden gloves.  This job often involves spreading the material with your hands, so protect them. 
  • A shovel or pitchfork, and a rake.  A bow rake is recommended, but a small leaf rake can be very helpful when you are applying light products and for giving your landscape a smooth, finished look.
  • A wheelbarrow is vital for moving a big pile or even moving a lot of bags.
  • A utility knife to open bags.
It is usually sold in bags in 2 or 3 cubic feet.

Step-by-Step Instructions

  1. Measure the area you want to cover and determine the square footage.  That’s the length times the width.  For a triangular-shaped area, multiply the height by the base and divide by 2, and for a circle’s area, you’ll need to multiply the radius times the radius times the 3.14 (remember “pi R squared” from geometry class). With irregularly shaped beds, you can find squares, rectangles, circles within and measure these sections and then add them all together. 
  2. Once you have determined your square footage, calculate how much you will need.  Products are sold in bulk by the cubic yard and also in 2- or 3-cubic foot bags.  One cubic yard will cover an area 10×10 (100 square feet) to a depth of two inches. 
    1. If you are buying 2-cubic foot bags, divide your square footage by 12 to give you the number of bags you will need.
    2. If you purchase 3-cubic foot bags, divide by 18.
    3. When buying by the yard, divide by 128.
  1. Write this number down the area of your space as well as the amount that you will need to purchase in your garden notebook.  If you need it in the future, you won’t have to remeasure.
  2. Weed. Weeds can keep growing through mulch, so spend a little time removing them.
  3. Edge.  If you plan to install any kind of edging, now is the time to do it.  If you have a hand-dug edge, freshen up the line.
  4. If you are using a pre-emergent weed control, this is when to apply it. It’s okay to use pre-emergents around trees and shrubs and in annual flower beds, but don’t use them when planting vegetables or ornamental perennial plants.
  5. Water.  Water your plants and water in the pre-emergent.
  6. Spread the mulch.  Use a shovel or pitchfork to place piles between and around the plants and use a rake or your hands to spread it evenly.  Do not let it touch the plants; leave a few inches of bare soil.  And certainly don’t bury your plants!
  7. Water again to settle it.
Spread around your plants, but avoid touching the base of the tree

Problems That Can Arise

Most problems come from applying too heavily.  A very thick layer can prevent air, water, and nutrients from reaching your plants. Over-applying can create soil that is much richer than many plants prefer.

Yellow slime mold can develop on hardwood products. It’s unsightly, but it doesn’t hurt your plants and it can be scooped away with a shovel. 

Slugs, insects, and rodents can set up residence and use this cozy cover as a home base while feasting on the roots, crowns, and stems of your plants.

A small garden that has been completed

Landscape Fabric and Plastic

Don’t use landscape fabric under organic mulches, which decompose over time.  The barrier created by landscape fabric prevents the composting bits from mixing with your soil. And, after a while, this layer of compost can become a germination spot for blown-in weed seeds.

Use landscape fabric when you are using inorganic products, like decorative stone or rubber nuggets.  This keeps the products from sinking into the soil.  And because these products do not decompose, there won’t be a layer of compost sitting between the fabric and the stones.

Don’t use plastic under any product – organic or inorganic. Plastic prevents water and air from reaching the soil, and this can kill your plants.

And, remember that, over time, fabric and plastic can come up, ripped and tattered and unattractive.  And with many pounds of product on top of it, fabric or plastic is very difficult to remove! 

Avoid using black plastic. It is not healthy for your plants and unsightly.
Do not confuse black plastic that is sometimes used to help warm the surface as mulch. Avoid using plastic as mulch

Remove Old Products

It’s recommended that old mulch be removed before adding new.  Piling it on year after year can smother your plants and prevent water and nutrients from reaching the soil. 

You can add the old stuff to your compost pile.

Say “NO!” to Tree Volcanoes

We’ve all seen them –  trees looking like telephone poles coming out of a high cone of mulch.

It’s so common that some people believe that’s how trees are supposed to be cared for.  Not so.

This practice probably came from years of re-mulching without removing the old.  Mulch should be applied around trees, not on top of them.  Leave a bare space about 4 to 6 inches away from the tree flare.

You should avoid making a mound around the trunk.
Do not stack as a mound around the base of your trees and plants

Another Alternative

As you know by now, any time the bare ground is present, nature wants to fill that space.  Often, those spaces get filled with weeds. As already mentioned, chunks of pine bark can be used to fill those spaces too. But there is a final option that can eliminate the need for mulch altogether – grow your plants closer together.

For example, using low-growing perennials and groundcovers – can be used to knit our gardens together and are much prettier.

Plants have evolved to create their own solutions to fill in space: the dead stems and leaves of the previous season’s growth.  It doesn’t have the same aesthetic as fresh, brown, shredded hardwood, but letting your plants grow in their own litter is an excellent way to keep them healthy.

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About the author: Alaine has been working way too hard in horticulture since 1992, beautifying golf courses, resorts, and hotels. She is a part time landscape designer who works full time caring for a 28,000 square foot public garden. At home, she maintains her own 400 square feet plot. Alaine lives in northern Illinois - zone 5b.

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