What’s the deal with bark mulch?

The deal with bark mulch is that it’s part of a worldwide yard-care conspiracy. Resistance is futile, so you need to figure out how you’re going to deal.

We strive to have perfect lawns; nice and green and trimmed all summer long. We like our lawns to be single-species environments – to be grass, all grass, and nothing but grass, even though grass, as a species, does not do well on its own. It does not return to the soil the nutrients needed for its own growth. So if you try to grow nothing but grass, sooner or later it gets really tired. Then you have to add nutrients. The Scott’s fertilizer people don’t tell you that it’s silly to grow just grass, because they want to sell you products to spread on your lawn which put the nutrients back. Your lawn would be happier if you were willing to let the clover grow interspersed with the grass. They are symbiotic – they feed each other. The Scotts people also want to sell you products to kill the clover, so don’t expect that explanation from them either.

Same deal with our planting beds. We strive to keep them clean and tidy of everything but the specific plants we want to see there. But that pesky nature thing is happening there too. Plants we don’t want in our planting beds are forever trying to grow there. Why? Little plants don’t care about big plants, just other little plants.  So there’s this nice open space without much competition from other little plants. They’re going to go for it. When they do, we call them weeds.

Basically a weed is anything growing where we don’t want it to grow. All those little plants that want to grow next to your rhododendron shrub are weeds. No matter how pretty they might be; they’re weeds. This leads us to the ultimate yard-care paradox. In your lawn, grass is to be loved and tended and encouraged. But in your planting bed – just inches away from your lawn – grass is a weed. Go figure.

Bark mulch is material you put around the big plants in your planting bed for three reasons:

  1. You hope, in vain, that it will keep little unwanted plants (a.k.a. weeds) from growing.
  2. An extra layer of fibrous absorbent material will hold moisture and keep the big plants happy.
  3. It looks so nice and tidy from the sidewalk.

Of these three jobs, wood mulch is really good at #3, pretty good at #2, and consistently disappointing at #1. That’s because weeds grow from seeds which are either already in the soil just waiting for an opportunity to germinate; or they will be deposited by wind, gravity or critters. Mulch will do a pretty good job of convincing the extant seeds that their opportunity to germinate has not arrived. But it’s fairly impotent against newcomers; to them, your mulch is just another growing medium waiting to be exploited.

Bark mulch used to be made of tree bark; not anymore. There’s not enough tree bark to go around, so they use wood pulp – probably the by-product of some lumbering process. It’s chopped up pretty finely and tinted in a variety of colors to be perfectly uniform.

You’ll want to spread the mulch at least a couple inches thick (three would be better) everywhere you want any of the three things listed above to be happening. Ta-Da! You’ve got a really nice looking planting bed.

How much to get? – Now there’s a really good question. For the geometry majors among you this will be really easy. All you need to do is calculate the area of the beds you want covered, multiply that by three inches and you’ve got the total volume needed. You can get mulch by the bag at your local gardening center, or you can get it delivered by a friendly man in a big truck by the cubic yard. If you figure you’re going to need three yards or more, call the friendly man with the truck. If you are not up for calculating the cubic footage of anything other than a square box (which your beds probably are not), the man with the truck will often have a website with a calculator to help you figure out your needs – though you’re still going to need a rough idea of the area to be covered.

How often do I need to go through this exercise? You can go several years between applications, but if you’re big on #3 above, you’re going to be doing it every couple of years. Like any other wood product, as soon as it is exposed to water, warmth, air and wee-beasties, it’s going to start to decompose – it’s going to become dirt. Furthermore, that pretty color the wood was tinted to make it nice and uniform, will fade, wash off, wear off or otherwise go away. The mulch is also going to move around. If you get a good rain it’s going to try to float away (hey, it’s wood remember). This is especially true on steep embankments.

There are alternatives to wood mulch. There’s rubber mulch made from recycled tires and there are rocks. The rubber stuff does not look very natural and it’s wicked expensive. It probably does fairly well at jobs 1 and 3, but it’s not going to be good at holding moisture. And who knows what chemicals it might be leaching into your soil. I’m not a fan. Like rubber, rocks are going to attempt jobs 1 and 3, but they are not known for their water absorbency. Both of these should last a lot longer than wood.

There you go. There are some important things to think about in the big beautiful world of yard maintenance – or maybe the whole topic is mulch ado about nothing.              Sorry.

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