Mulch Madness

Just about the time we should be enjoying the all too popular college basketball tournament we are sure to see the first truckloads of mulch appearing in driveway turnarounds around town.  There is nothing quite like a steaming pile of fragrant mulch on a cool spring morning… kind of makes me all warm and fuzzy inside just thinking about it. 

Unfortunately, there are some common misconceptions and misinformation about mulches that I would like to help straighten out. 

First, I realize that many of you just want to get the task of mulching done and out of the way early in the spring, but you can be causing more harm than good in doing so.  Applying mulch over cold, wet soils prevents them from warming up and drying out normally and therefore can cause long term damage to the roots of plants.  Additionally, you should avoid walking on wet garden soils which causes compaction, plant stress and possible root damage. Of course the weather is not predictable so the best time to mulch will depend on the season, as well as your particular location, but generally we find most soils do not dry out much before mid-May. 

The next most common mulching mistake is applying too much mulch.  If 2” is good 4” must be twice as good… right?  Actually, anything thicker than simply covering the soil surface is not beneficial and can be detrimental. We often find there is more than enough existing mulch in many beds that only requires a thorough stirring to make everything look fresh and clean.   

Here’s one that you have all seen before… volcano mulching.  Volcano mulching is when mulch is piled over the trunk of trees or stems of shrubs burying the surface roots of the plants.  This is the most common reason for urban tree death.  Sadly, many “professionals” are guilty of this and municipalities are notorious for volcano mulching.  Every tree naturally forms a root flair where the root structure extends from the trunk of the tree. This flair must remain exposed or abnormal root growth can and will destroy trees over time.  Likewise, many shrubs, perennials and groundcovers can be also smothered with too liberal an application of mulch.   

Mulch can be composed of many different materials and each has its own features and benefits.  The most common mulch material in this part of the country is hardwood bark.  The advantage to hardwood bark mulch is its ability to hold down weeds and help soil to retain moisture during periods of drought.  The down side to hardwood bark mulch is that it can choke out tender annual flowers. 

Recently there are many recycled wood mulches available that are sold as hardwood mulch.  Old pallets, building debris… any wood waste available can be ground up and sold as mulch.  Unlike bark mulch, as wood mulch decomposes it competes with your plants for essential nutrients and therefore is not generally considered plant-friendly. Most of the dyed mulches of various colors would fall into this category.  It is not uncommon to find paper, plastic, nails… all sorts of garbage in these recycled wood mulches.  Another drawback to black painted mulch is this material absorbs heat making soil temperatures higher than normal.  Although these painted mulches are gaining in popularity I do not recommend them. 

Pine bark mulch is a great product but the major drawback is the cost in transporting this product from the south where it is produced. Pine bark mulch is best for use around annual flowers because it does not form a dense mat that can choke these tender plants.  Pine bark also has the benefit of naturally forming resistance to root rot diseases within garden soils as it breaks down.  Pine bark is available as mulch, as well as in small and large nugget forms.   

Compost is another mulch option that has become more popular in recent years.  Compost may contain a wide array of ingredients from grass clippings to leaf humus, wood chips to animal manures.  The benefit to compost is that it helps build soil fertility and vitality making plants grow like crazy.  The homeowner who wants to weed less will not be as happy with compost that is not as effective at suppressing weed growth as other mulches are.   All composts are different and some are better used as mulches than others.  Look for material that has a bit of coarseness and avoid unscreened material that will not have an even texture once applied. 

Pine straw mulch is less commonly available here but a very attractive option.  Long pine needles offer a wonderful texture and hold up well in the landscape.   

Decorative gravel and rock present an excellent mulch alternative especially where plant growth is limited due to adverse conditions.  Consider gravel mulch around large trees with aggressive root systems, on steep grades, anywhere erosion may cause mulch to drift, playgrounds and other places where there is heavy traffic. 

Well that is likely more mulch madness than you had bargained fo, but many of these issues come up again and again so they probably bear repeating this time of year.  Proper mulching can make your garden more beautiful, improve your plants’ health and eliminate a ton of unnecessary garden work.   

Now go outside and have fun in the dirt!