“You are what you eat” is an old saying, and it points the way to picking the right mulch for your landscape. It’s common sense that if you add several inches of anything to your gardens each year it will affect the soil quality over time. We like to say “whatever you spread on your landscaping each year, that’s what your soil will become”.
Mulch suppresses weeds by preventing the sun from reaching weed seeds. It won’t help with deep-rooted perennial weeds that are already growing. If you introduce weed seeds into or on top of the mulch, for instance by blowing clippings onto it or digging up the underlying soil, you’ll have weeds. Most people don’t spread mulch thick enough, or do the housekeeping to clean up the beds before mulching. Think of weed seeds as germs, and do your best to keep the mulch clean
All mulches are not equally effective at weed control. Fine-ground mulches are much like potting soils; wind-blown weed seeds or blown grass clippings will sprout and root easily. Course bark mulches or “nuggets” aren’t so friendly to weed seeds, and they last much longer before turning to soil so they make better weed barriers for a much longer period. That makes them ultimately cheaper, because you need less in future years.
Good mulches turn into soil eventually. Some mulches are much better for your plants than others. For instance, most plants prefer “acid” soils, so pine bark is healthier for them than hardwood mulch, and much healthier than dyed wood chips. Many mulches contain recycled pallets and other waste wood. These can be bait for termites, and actually rob your soil of nutrients as they decompose. The ideal mulch should improve your soil, turning into rich humus that can be tilled in to loosen compacted soils and clay.
We’ve tried many mulches in our gardens over the years, and we’ve settled on pine bark for our own landscape. We like to use shredded pine bark on new plantings, and then switch to larger pine bark “mini nuggets” after a few years because it lasts longer and discourages weeds better. Another thing we like about pine bark nuggets is that even when they’re wet they “breathe” instead of packing down, and they dry out quickly which discourages fungus diseases.
Pine bark mulch has a low PH, which means it is good food for evergreens, blueberries, dogwoods and other acid-loving plants. Mulching your beds with pine bark year after year will build your soil very nicely. Finely shredded, composted hardwood mulches like are next best. Proper composting kills weed seeds and diseases, so you’re not importing problems into your landscape. Poor quality mulches are more likely to breed funguses and mushroom colonies.
We use shredded, dyed virgin hardwood on most of our landscape projects. This mulch is a by-product of Amish pallet shops, which shred their scraps and dye it black with soy ink to make high quality mulch totally free of weed seeds. Since this mulch is 100% clean dimension lumber cutoffs, not recycled wood, it’s consistently clean and pure without composting.
Over the years we’ve seen mulch fads like recycled shredded tires and ground cypress roots. If spread thick enough, these by-products will suppress weeds, but they don’t bio-degrade so they won’t improve you soil. Your plants won’t appreciate being smothered by non-compostable mulches. These products work fine for paths and play areas, but they are poison for gardens.
The first step in shopping for mulch is figuring out how much you need. Figure out how many square feet of beds you have to cover by multiplying how many feet long times how many feet wide. For three inches thick of cover you’ll need one cubic foot of mulch for every four square feet of beds. One cubic foot for every six square feet will give you a two-inch thick mulch job. Most mulches come in 2 Cubic foot bags, although convenience stores and mass merchants are now stocking smaller bags so they can advertise a lower price per bag.
All mulches are not equally good for your garden, and some can be downright harmful. There’s no requirement for labeling to disclose what exactly is in the bag. You get what you pay for with mulch. Smart gardeners choose mulch very carefully, and don’t just buy the cheapest thing they can find. If you buy bulk mulch, pay attention to how it’s stored and handled. Are there lots of weeds going to seed in the vicinity? Is the loader bucket and storage area muddy and messy? Likely there are weed seeds in the mulch already, possibly even hard-to-control field weeds like thistle, and you could be importing them into your yard.
Your landscaping looks best with a blanket of fresh, dark mulch. If you follow these tips, your investment in new mulch will give you more than just good looks. It will benefit your plants and save you many hours of work.
Steve Boehme is a landscape designer/installer specializing in landscape “makeovers”. “Let’s Grow” is published weekly; column archives are on the “Garden Advice” page at www.goodseedfarm.com. For more information is available at www.goodseedfarm.com or call GoodSeed Farm Landscapes at (937) 587-7021.