Earthy Diversity: Mulch Types and Tips

When you think of mulch you may have memories of the foul smelling stuff covering your elementary school playground that would stick to your socks and get into your shoes, or that particularly smell in town in early spring when they decide to mulch every tree and shrub in existence.

Mulch doesn’t need to smell bad, and it can be used to perform near miracles in your garden. What more could you want?

Benefits of mulch

Mulch is essentially anything that is used to cover the soil. Woodchips, cardboard, cover crops, plastic, paper, leaves, compost, plant debris, etc. We’ll also be going over some of the biodegradable types of mulch (plastic mulch that claims to be biodegradable actually just breaks down into microplastics and is detrimental for soil biology). 

So, what makes mulch so great for your garden? Well, mulch provides different types of benefits, like keeping the soil moist (which conserves water and keeps plants and soil biology happy), weed suppression, adds organic matter (OM) to the soil, and helps prevent soil erosion from wind and some rain. Pretty great, right?! 

Types of mulch

With so many different options, how do you know which one you need? An easy rule of thumb to follow is the larger the size, the longer it will take to break down. The smaller and lighter it is, the faster it will break down.

This means if you want to put wood chips on your pathway to suppress weeds, you probably just want to do a single application for the entire season rather than every few months. That means you’ll want to go with the largest size material you can find.

For topping perennials, you’ll want weed suppression but you also want it to break down to add OM to the soil, so a medium size is a good fit.

For topping your actual garden beds, a medium-to-fine size is great for quick breakdown if you’re okay with adding another layer or two throughout the season or whenever you flip the bed for new crops. 

 

My personal favorite wood-mulching method is to make and use ramial chips (running small branches/ branch tips through the wood chipper to make a nutrient dense, light and fluffy mulch) on my garden beds. The worms go crazy for it and break it down completely in a single season, leaving behind a layer of black worm castings.

If I don’t have any ramial chips on hand, I put down a layer of leaves followed by a balanced organic fertilizer topped with aged hardwood bark mulch from a local supplier. I’ve found the worms aren’t as crazy about the aged bark mulch, so as the leaves begin to break down, the worms move in and work their magic. The reason for adding the fertilizer is to help with any immediate nitrogen issues from applying the mulch (see Key Notes). 

If you don’t have access to a local mulch yard, or you don’t want to spend money on bags of mulch from your local home improvement store, you can just simply use cardboard, intact or shredded paper, or leaves.

When using paper, make sure it’s not glossy magazine paper. If you’re using paper from your shredder, make sure that there are no credit cards or other non-paper pieces in there.

When using cardboard, make sure to leave a gap right around the base of the plant so water can easily penetrate through. Any combination of these will work wonderfully too. You can even use paper bags at the grocery store and just lay them down on top of the soil.

Just note that with paper, leaves, and cardboard, you may need something to hold them down for the first few weeks since they will blow away when dry. After they’ve started to break down you won’t need to worry about that so much. The more moist they stay, the faster the decomposition process will be. 

How to mulch

When mulching around plants, be mindful of the type of plant, how biologically active (hot) your mulch is, and what time of year it is.

When mulching around trees, it’s important to make sure you do not mulch all the way to the trunk or up the trunk. Mulch on the tree trunk can trap moisture there, causing the trunk to rot, ultimately killing the tree. This is especially true when the tree is grafted since any trapped moisture at the graft line will very quickly kill the tree. This concept is true for all “woody” stemmed plants

Mulching around most garden plants in spring is a little different. So long as your mulch is not hot (literally, you can stick your hand into the pile and if it is hot then you need to be sure to very thinly spread it out so it doesn’t cook your plants), and it is not hot outside yet, you can actually put a good few inches around the base of the plant.

Make sure to leave a few inches clear around the base of the plant if utilizing this mulching method. Also covering the green material with a layer of wood chips will help balance the excessive nitrogen present in this decomposition process. 

Many garden plants are adventitious rooters which means they will grow new roots from their stem. The most well known practitioner of this is the tomato. Many other plants do this too which means that if you plant or mulch them deeply they can actually develop more roots, leading to a more robust plant. If it is hot outside though, this can actually trap too much heat and kill the plant. When in doubt, just spread an inch or two and don’t pile it up around the base of the plants. 

Key notes

Aside from being aware of the temperature of your mulch and the outdoors, also be careful about nitrogen lockup.

Nitrogen lockup will stunt or kill your plants which is the exact opposite of what you want! As the microorganisms in the soil consume the carbon in the wood chips, they use the available nitrogen in the soil as a part of this process, meaning the plants are not able to get enough for themselves. Adding a balanced fertilizer to the soil along with the application of the wood chips can help counteract this nitrogen deficiency.

Play around with the thickness of your wood-based mulch layer, the age of the mulch, and adding or not adding fertilizer. Take notes of how the plants do in order to figure out a system that works best for you and your garden. Be your own garden scientist!