As we head into Spring, I'm again confronted with confusion about mulch versus bark, nuggets versus chunks, wood chips versus hardwood mulch, bark dust versus - wait: bark dust?
Oy!
Which layer of mulch is the better option for my garden? I went looking for answers.
First, the basics: what is mulch? Then the focus is on the production, uses, pros, cons of commonly used organic wood mulches - bark, wood chips, and hardwood mulches.
Curious about rumours that there could be wood pallets and old furniture in your bag of mulch? Read on!
What Is Mulch?
Mulch is a top dressing that you layer over the soil in your garden beds, flower beds, vegetable gardens - wherever you want to:
- eliminate weed growth and insert weed control;
- stop soil erosion;
- build soil quality;
- stop water loss through evaporation and bolster soil moisture;
- regulate soil temperature to protect plant roots;
- add texture and color to your landscape design.
There are two different types of mulch:
- mulch made from organic matter;
- mulch made from inorganic matter.
Organic Mulch
The different materials that fall into the category of organic mulch are organic matter. This type of mulch supplies nutrients to the soil as it decomposes, increases moisture retention, acts as a weed barrier and more. It's the best mulch if your priority is to promote plant growth and health.
Examples:
- tree bark that's turned into bark chips such as pine nuggets, and bark mulches such as cedar bark mulch
- processed wood products that are shredded and/or ground
- softwoods such as wood from pine trees and cedar trees
- freshly cut wood that's gone through a chipper to create wood chips
- pine needles (also known as pine straw)
- leaves that are shredded into leaf mulch
- grass clippings
- straw and hay
- hulls such as buckwheat hulls and cocoa bean hulls
- nut shells such as pecan nut shells
- newspaper
- cardboard
Inorganic mulch
Inorganic mulch can offer your garden many benefits. Some types, like plastic sheeting, are the best option if you're concerned with keeping weed seeds from sprouting. But it doesn't build soil quality since it doesn't decompose over time.
A main difference between organic and inorganic mulch is that inorganic mulch sticks around. You won't have to replenish stone mulch or rubber mulch annually or every few years as you would organic mulch. If one-and-done is your goal, an inorganic mulch is an excellent choice.
Examples:
- river rock
- stones in a variety of sizes
- lava rock
- gravel
- chipped rubber
- plastic sheeting
- landscape fabric and geotextiles
Using Bark As Mulch
According to the Mulch and Soil Council, bark is "The corky exterior covering of trees, including the cambium, with a maximum wood content (interior xylem) of 15%." (Source)
Mulches that are made from or include bark are bark nuggets, bark mulch, and bark dust.
Nuggets
Bark nuggets that we typically buy at box stores and garden centers are made from the bark of trees such as fir, pine, redwood, and spruce woods. The bark is removed during the lumber milling process. (Source)
You can get nuggets in large and small chunks. Pine bark nuggets are a common option though there are other Western bark nuggets from conifer (cone-bearing) trees found in North America's western region.
Pros
- Tend to last years, especially the variety that comes in bigger chunks.
- Maintain their natural color and don't turn grey like other organic wood mulches.
- Some bark nuggets, such as pine bark nuggets, are great for plants that thrive in acidic soil.
- Maintain their shape and don't compact.
- Are widely available.
Cons
- Better for areas where you won't need to move them like around a tree trunk and under shrubs.
- Float in water so it's a good idea to use them on level ground where they won't be submerged in water or washed away in heavy rains.
- Wood loving pests like termites can set up house in bark nuggets.
Bark mulch
Bark mulch is made from the aged bark of hardwood trees such as oak, hickory, ash, and hemlock, and softwood trees such as fir, pine, cedar and spruce.
Bark mulch may contain nuggets or chunks but it's shredded, sometimes double-shredded, and so also has a stringy, more broken down quality.
Pros
- It's widely available.
- The different woods used offer different colors and hues naturally, not dyed so you can choose from different colors to suit your garden design.
- Since it's shredded it will break down faster than bark nuggets.
Cons
- The bark mulch of hardwood trees can add alkilinity to your soil which your acid-loving plants won't like.
Bark dust
New to me (but not to Pacific Northwest gardeners and landscapers) is bark dust.
Bark dust is commonly made from the bark and wood of cedar, fir, pine, spruce, and hemlock trees that have been ground into small particles to fine granules. (Source)
You can spread the stuff yourself but, due to its fine profile, many companies use blowers to put bark dust where it's needed.
Pros
- The different woods used offer different colors and hues naturally, not dyed. Choose from different colors to suit your garden design.
- It can provide a soft, splinter-free landing in children play areas.
Cons
- DIY-able but perhaps not super DIY friendly.
- Widely available in the Pacific Northwest; not as common in other parts of North America.
Using Wood Chips As Mulch
Wood chips are an organic material made from hardwoods and softwoods.
Wood chip mulch is usually lower in cost than shredded wood or bark options. It's possible to get your hands on wood chips at no cost if you know where to look and who to ask.
If you get a free pile of wood chips, note that it might contain parts of the whole trees - chipped trunk, bark, branches, leaves, needles, pine cones.... This is because free wood chips are a by-product of tree trimming and removal work. The chipping makes whatever was chopped down easier to transport and dump.
Pros
- Affordable - can be obtained inexpensively or free.
- Help local small landscaping and tree trimming companies save on gas and landfill fees when you take wood chips off of their hands.
Cons
- If it's the free stuff, you have no control over what you get or when you get it.
- Fresh wood chips can take nitrogen away from your soil and plants as it begins to decompose. Therefore, it's best to use wood chips in places like walking paths and not in vegetable or flower beds.
Using Hardwood Mulch
Typical hardwood mulches - the kind you find at Home Depot and other stores and garden centers for about $3 to $4 per bag often dyed red, black, or brown - are organic mulches that are a by-product of lumber production.
Hardwood mulch can include shredded recycled wood such as wood pallets, furniture, and decking. If you're buying mulch made from recycled wood make sure it's safe. Look for the Mulch & Soil Council's seal on the bag to verify that your mulch doesn't contain contaminants.
Pros
- Mulch made from recycled wood is eco-friendly.
- Affordable.
- Widely available.
- Choose from different colors to suit your garden design.
Cons
- Can include woods that were chemically treated.
Looking for a way to contain all of that mulch? Check out 2xEDGE, easy to install garden edging - no digging or drilling!
