How to Apply Mulch Properly

  • Gardener working in the garden doing the mulching
  • Transcript

    LESLIE: How can you help a newly planted tree grow? Well, it needs mulch to protect its roots and prevent weeds.

    How to Apply Mulch ProperlyTOM: Ah, yes. But there can be too much of a good thing when it comes to mulch, at least when it’s applied the wrong way. Here to tell us more is This Old House landscaping expert Roger Cook.

    Welcome, Roger.

    ROGER: Hey. Thanks for having me.

    TOM: Now, this is a project that many of us do every year and I think that folks tend to over-apply it or at least apply new over the old. And before you know it, you have these big sort of conical piles of mulch around trees. That’s not really doing them much good, is it?

    ROGER: I hate mulch volcanoes.

    LESLIE: Is that what they’re called?

    ROGER: They’re a scourge. I call them that. Scourge of my life. Everywhere you drive, you see them. And it comes from a couple of different things. First, it comes from the landscape. Edging around the tree with his edger and he flicks the soil and grass up on top of the tree. And then because he did that, he has to put a wad of mulch on top of it to hide it. And year after year after year, it just builds up around the tree.

    TOM: So what’s the best way to replace your mulch? Should you dig it out, down to grade, every single year?

    ROGER: You don’t have to take it out every year but every two or three years, yeah. Take it away. And then when you put it in, just put it in by the handful. Too many people come over and dump a whole wheelbarrow on top of the tree. And because they dumped the wheelbarrow, that’s what they use and it’s way too much mulch.

    LESLIE: So if you’ve got too much mulch, are you in danger of suffocating the whole root system or just putting too much moisture? Other than looking funny, what’s so bad about it?

    ROGER: All of the above. It just compromises the root system. It can compromise the trunk of the tree. It can compromise the root flare. Ultimately, you can end up with a thing called “girdling root,” which is a tree root that actually grows right around the trunk of the tree. And over time, it will strangle it and kill it.

    TOM: Let’s talk about the types of mulch that are available. You know, you have hardwood, you have rubber mulch. There’s just so many choices today. What plays into the choice of the materials for your house?

    ROGER: Ninety-nine percent of the time, I’m going organic. Some sort of pine mulch is great but I don’t like the red-colored mulch.

    LESLIE: Oh, me too. I don’t like it.

    TOM: It doesn’t look natural.

    ROGER: When you look for mulches, you want to make sure it’s mulch. It’s just ground-up bark and some wood, not something that’s been treated or painted or stained or anything like that.

    TOM: I’ve also heard that there’s funguses, like shotgun fungus, that sometimes is attracted to the manufactured mulch but you really won’t find it in the natural, organic mulch.

    ROGER: Yeah, I’ve heard that too. And it’s pretty wild to see how far those things shoot up on a building, isn’t it?

    TOM: Yeah. And they can – they look, basically, like a shotgun kind of blast. And they’re very, very difficult to get off.

    ROGER: But there are other things you can use for mulch, too. You can even use a groundcover for a mulch. It’s great. You can put pachysandra, something like that, or some of the more aggressive plants because they are going to be fighting that tree for root – for water and nutrients.

    TOM: So I guess the mulch really serves that tree year-round. In the summer, it’s going to help hold the moisture in. In the winter, it adds a little bit of insulation to the root ball, right?

    ROGER: But the most important thing it does is it keeps the lawn mower and the string trimmer away from the trunk or the tree. Too often, you’ll have people that let grass grow right up around the trunk. And then they’ll come by and go to trim it away or try to cut it with a lawn mower. They’ll gouge the bark of the tree and eventually, that can lead to decay and a tree that ends up suffering and dying.

    TOM: But not on your watch.

    Roger Cook, the landscaping contractor from TV’s This Old House, thank you so much for stopping by The Money Pit and helping us to keep our trees healthy.

    ROGER: I hate mulch volcanoes.

    LESLIE: Alright, guys. You can catch the current season of This Old House and Ask This Old House on PBS. For local listings and step-by-step videos of many common home improvement projects, visit

    TOM: And Ask This Old House is brought to you on PBS by Mitsubishi Electric Cooling & Heating. Make comfort personal.

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