How to kill grass on a playground?

August 12, 2009 11:47 AM

How to kill grass on a playground?

We recently installed a wooden playground set in use by about 20-30 kids each week. After laying down about two layers of landscape fabric on top of grass, we put about 2" of rubber playground mulch over it.

The problem is that grass and weeds are still growing up through it. In hindsight, we probably should have killed off the grass before putting down the fabric. Now it would be an incredible task to move all the rubber mulch, lift all the fabric, kill the grass and put it back on all over again.

It's been suggested that we use Roundup to kill all the grass, but I wonder if this is safe since children will be using the playground in the future.

The mulch with grass growing through is quite unsightly, but maybe something we just have to live with.

What should we do? Any ideas?

posted by roaring beast to home & garden (23 comments total)

Is it in the front or back of the house? Or rather, is it in a part of the yard where people can easily get to without bothering you? Because (assuming there aren't any weird liability laws that would come into play) you could always open up your yard as a doggy bathroom and let people bring their dogs there to pee.
posted by theichibun at 11:51 AM on August 12

As a parent I'd rather you just left it instead of spraying any herbicide on it.
posted by bottlebrushtree at 11:52 AM on August 12 [1 favorite]

Between the mulch and kids constantly running around on it, it will probably die off on its own. If not, would covering it with an opaque tarp for a couple of weeks work?

Good on you for avoiding the chemicals.
posted by rumsey monument at 12:04 PM on August 12

Roundup is by far the easiest solution and I'm sure it's what lots of places use in similar situations; if that's really not what you want to do, I think your alternatives are basically ignoring the grass/weeds and either cutting them repeatedly, or using a weed burner or similar contraption.

You'd need to obviously use caution with a weed burner over mulch, but if you wet the mulch first (or did it after a good rain), I doubt very much that you'd get it burning. (It might depend on the mulch, so you might want to try a pile of it spread on asphalt to be sure.) I've seen guys using those things over wood chips and near fenceposts without problems, but I'd guess you have to be careful to not keep the flame in any one place for a great deal of time.

If that seems too risky (and frankly I'm not sure I'd bother), I'd say just ignore the grass, or trim it back as often as you can and see if that at least keeps it manageable.
posted by Kadin2048 at 12:05 PM on August 12

I'm not sure practical this would be for your playground, but I use boiling water from a electric water kettle to kill the weeds/grass that spring up from time to time in my driveway and gravel walks. You need the water to be very hot when it is applied so it can "Cook" the weeds which seems to kill pretty much anything.

I'm not sure if there would be any reaction with the rubber mulch, but I would not think it would be dangerous.

No chemicals = good.

But it isn't a apply once type of scenario either. I find that I have to apply the water about once a month in the summer. I do not know if it is new growth or roots regenerating leaves, but for my area it is manageable.
posted by Hollowman at 12:07 PM on August 12

theichibun: "...you could always open up your yard as a doggy bathroom and let people bring their dogs there to pee."

You did see that this is a playground, right? Not a good place to encourage dogs to hang out at all, and especially not to relieve themselves.
posted by The corpse in the library at 12:09 PM on August 12

Since it's rubber mulch I'd recommend against using flames to kill the weeds. Roundup is not the best choice for the environment but unless the kids are rubbing their faces and liking the ground it's not going to be particularly problematic. If you use Roundup, just do it when kids won't be playing there for a few days then hose down the area.
posted by Burhanistan at 12:11 PM on August 12

Oh, and a "dog toilet"? That is truly a terrible idea.
posted by Burhanistan at 12:12 PM on August 12

How much time do you have?

What you want to do is "solarize" the soil for a few weeks. This heats it up and kills the grass. The more heat, the faster the killin'.
posted by adipocere at 12:15 PM on August 12

How about using vinegar instead of the chemical alternatives?
posted by alynnk at 12:21 PM on August 12

You can always salt it. That's kid-safe and plant-hostile... as long as you never want to grow anything there again.
posted by rokusan at 12:22 PM on August 12

I would scrape away as much of the mulch as possible, and then treat it with Roundup, and then put the mulch back.

Although I have no love for Monsanto (I think they are evil, actually), I can't get excited about Roundup, knowing what I know and having talked to a number of independent toxicologists about it.

Unless your property drains directly on a waterway, there is nothing to worry about, leaching-wise.
posted by Danf at 12:27 PM on August 12

Pay the kids a penny per weed/grass stalk they pull up.
posted by jwells at 12:31 PM on August 12 [1 favorite]

Hm, so far the tarp idea stands out to me. Any ideas on how long it would take to kill everything? Also, how often I'd have to repeat the process?

I'm gonna rule out the dog toilet and flame options (not good with rubber mulch).

Another thought to consider is using a different type of bedding. For example, would adding regular wood mulch work, or would that have weeds too?
posted by roaring beast at 1:01 PM on August 12

Are you sure the new grass is growing through the landscape fabric and not above it? I think it may be more likely that dirt has settled in the rubber mulch along with windblown grass/weed seeds and sprouted.
If so, it should be easier to remove by pulling it out, since it won't be anchored to solid ground and the roots should be shallow.
posted by rocket88 at 1:08 PM on August 12

Wood mulch won't get rid of grass. I speak through experience.
posted by The corpse in the library at 1:17 PM on August 12

FWIW, I've worked in Parks and Recreation for the last 11 years, and RoundUp has always been the answer to this problem on the municipal playgrounds I've maintained. Once it's dry, there's very little risk to the kiddos who might come into contact with the weeds. It's a systemic herbicide, so it will kill the whole plant.

20 grain vinegar would work, as well (as long as you don't mind your playground smelling like a pickle for a while). Salt water would probably do the trick, too.

If it were me, though, I'd use RoundUp.
posted by Shohn at 1:35 PM on August 12 [1 favorite]

Pouring vinegar on the weeds can also kill them (maybe combine the boiling water and pour boiling hot vinegar). They'll die, shrivel up, and then will be very easy to pull. This also works really well on sidewalks.

Round Up has a really short "half-life" as it were. I'd keep the kids off it for 24 hours, but after that it'll be fine. However, you don't need it. Vinegar works just as well.
posted by nax at 2:29 PM on August 12

Do people not weed anymore? I would just spend an hour or two, or three, weeding it. Get the kids involved and have them get inspired by taking care of their own playground, it might empower them by inspiring them to contribute.
posted by Vaike at 3:26 PM on August 12

Do people not weed anymore?

If you pull weeds up through plastic bed liner, it creates holes in the liner which just allow more weeds to come through. Killing them in place with herbicide doesn't damage the liner. (Of course if they're actually growing on top of the liner, in the mulch, that's a different story. But it doesn't sound like that's what's happening, although you'd need to dig a few up to be sure.)

Weeding is the proper response to weeds in a garden, but in a purely mulched or gravel area where you have previously put plastic down, it can do more harm than good.
posted by Kadin2048 at 3:56 PM on August 12

Creates bigger holes in the liner, rather. Obviously there's some size hole there already, which the weed either created or exploited in order to grow in the first place. But if you pull the roots up through it, you might make a tiny hole into a relatively large one, or worse yet into a long linear tear.
posted by Kadin2048 at 3:57 PM on August 12

This is probably the only sort of situation where I endorse Round-Up. Pick a very dry, calm day, so you don't have to apply it often, and it stays where you spray, and kill the weeds. Round-Up is inert once in the ground, so as long as you apply it very selectively, it's not that bad.

I haven't had any luck with vinegar in controlling the thistles I have in my backyard, so I use Round-Up on those, just to prevent getting notices to comply from the city. YMMV.
posted by Kurichina at 8:26 AM on August 13

Salt water. Supersaturated salt water.

Works.

Every.

Time.

(Except when it doesn't.)


Seriously. Use salt water. Rock-salt water works great too.
posted by TomMelee at 12:57 PM on August 13