To Mulch or Not To Mulch

Mystery Mulch Unmasked!

Mulch is any material you use to cover a garden bed in order to preserve moisture, moderate the soil temperature, and suppress weed growth. All types of mulch are grouped into two basic categories, organic and inorganic. Types of organic mulch include compost, hay, leaves, wood chips, bark, peanut hulls, pine needles, animal manure, ground corncobs, and even recycled materials such as recycled wood or paper. Perhaps the most commonly used form of inorganic mulch is crushed stone. Plastic or fabric sheeting is often also used, sometimes in conjunction with other organic mulch such as wood chips. Both organic and inorganic mulches sold in retail stores are commonly little more than reclaimed industrial waste, as is the case with wood chips, which land developers must pay to get rid of before retailers bag it and sell it to us. Some of the newer post industrial waste products available for adventurous gardeners include shredded tires, aluminum foil, and my personal least favorite sewer sludge. For our gardening purposes here we will make one more distinction amongst mulches as we separate them into the categories of summer and winter mulch. Summer mulches are most of the above listed items such as wood and animal manure, while winter mulches are those temporary mulches such as leaves or hay, which we use to insulate our northern gardens from the drying winter wind and sun. Now that we know what we’re dealing with here let’s have a closer look at some of the more commonly used mulches.



Okay so I’m starting with my obvious favorite.  As anyone who has read any of my previous Seed articles can tell you compost is a garden necessity.   Well-balanced compost will have microbes, which form large underground fungi that feed and protect garden plants.  At the same time compost offers the perfect fluffy soil texture that roots need to easily grow.   When applied to the garden in the spring time the rich color of compost will catch the warmth of the sun and awaken the plants so that the garden is quickly covered in green before the summer heat gets a chance to bake the moisture out of the soil.   Compost can be made at home or purchased through retailers. My favorite compost for large garden projects is a product called Farmpost which is a mixture of animal manure, hay, leaves, and a little bit of wood chips.


Wood chips, shredded wood, and chunks of bark are all different types of wood mulch that are available through any local gas station, hardware store, or big box retailer.  These products are sold in a veritable smorgasbord of colors, with a few companies out there willing to dye your mulch to match your trim and shutters.  But unfortunately for so many of us who’ve bought into the idea of smothering the ground in shredded tree, wood mulch can be quite problematic.  For starters many types of wood mulch have a high carbon to nitrogen ratio, so that while they sit on your garden bed and naturally decay they rob the soil of nitrogen that the plants rely on for growth.  Decaying wood will carry with it a host of organisms with undesirable traits or O.U.T.’s, as I like to call them.  Some of these O.U.T.’s include; slime molds and other detrimental fungi which are poisonous to plants and can be rather nasty looking, termites (who invited them to the party?), and rodents who find traveling just beneath the wood mulch a convenient way to get to that yummy tender bark around your new trees and shrubs.  With any finely shredded wood mulch too little oxygen and water enter the ground, and with more coarsely ground mulch too much water can be retained.  From my point of view wood mulch is best kept out of the garden, and onto the path where it makes a nice soft walking surface in which weeds don’t like to grow.


Next time you’re at the gas station, have a look at whatever landscaping is there and I’ll bet you will be looking at crushed stone.  Stone mulch is commonly used in applications where the landowner desires a very “low maintenance” landscape.   Unfortunately however it would seem that by replacing the sales tag “low maintenance” with “replant your trees and shrubs every three years” the folks who sell rock mulch would be giving us a little more accurate perception.  For this example we only need look to the woods or the prairie or the jungle.  In none of these lush, verdant environs is found a ground covered in stone.  Yes forests did grow upon the Rocky Mountains, but those took a while to establish, perhaps a few thousand more years than you’ll have to invest in your landscape.  In fact when we look around to find a natural environment covered in crushed stone it would seem the barren desert is as close as we come to that.  Crushed rock will bake the water out of your soil, overheat the plant roots, and over time compact soil.  But then, nobody really expected that gas stations would be a good source of landscaping inspiration did they?


Skip it.  It’s that simple.  Both of the fabrics stifle airflow in the soil.  Both of these products run water away from the soil.  Both of these products block new nutrients from entering the soil.  Just skip it.  If you didn’t already skip it, then pull it up and skip it next time.


When people start covering their gardens, lawns, and play areas with dangerous chemically laden post consumer industrial waste, and paying for it as though it were a privilege I feel there must be some smirking marketing executive somewhere who really needs to have their creative license revoked.

As it turns out the road to answering the question “To mulch or not to mulch?” can be really quite tumultuous.  One must avoid clever marketing executives and other types of slime molds.  You may have thought your garden was covered only to find your nitrogen was being stolen for years.  After reading this you may even feel as if your gardens are lost in the desert, and that a good mulch is nothing but a mirage, but rest assured your oasis awaits if only you’ll think globally and compost locally.