How to Control Weeds Between Wooden Deck Boards

LESLIE: Randy in Texas needs some help with some yard work, with weeds between wooden deck boards. Tell us what’s going on.

RANDY: Yes, ma’am. What I’ve got, I’ve got a 30-foot by 15-foot pressure-treated deck on the back of my house. And where the wood has shrank or shrunk and given me gaps between the 2×6 boards, I’ve had leaves fall in there and I can’t get – I have no way to get them out without taking the deck up, which I don’t want to do. Is there some way that I can put some kind of organic matter or something in there to break down the leaves so I don’t have sprouts coming up?

TOM: So you’re saying that you have organic matter that’s stuck between the 2×6 floorboards of the deck and they’re starting to grow?

RANDY: The deck itself is sitting on a concrete patio. And then I’ve got 2x4s laid on edge and that’s what I built the deck on.

TOM: Oh, so it’s basically a wood platform, like a pallet on top of a patio.

RANDY: There you go.

TOM: Yeah. No wonder it’s so moist. Well, listen, I mean that’s a real unusual assembly and there’s good reason for doing it – not doing it that way, because of what you’re seeing – weeds between wooden deck boards. You’ve got a lot of moisture issues here.

I don’t have a good solution for you, because it’s just a non-traditional way to assemble a deck.

RANDY: Without having – it had to be that way, otherwise it wouldn’t match up with the floor. I’d be elevated above my floor, my elevation of the house itself.

TOM: Mm-hmm. Right.

RANDY: I’ve heard putting dry molasses. Would that help?

TOM: I have no idea.

RANDY: OK.

LESLIE: I don’t know. I feel like that might attract some critters of some sort.

TOM: Yeah, some ants. Definitely ants and stuff.

You have a wood-framed deck that’s basically built flat on top of a concrete surface. The concrete is going to stay really moist and damp, which is one of the reasons that it’s such perfect, almost greenhouse-like conditions for you to grow plants through there and see weeds between wooden deck boards.

One of the things that you could do is you could use a product like Roundup, which is a herbicide that will – you know, once you spray it, it will stop – it will kill things and stop it from coming back.

LESLIE: Kills a lot of things.

TOM: Right.

And you also might want to try Spray & Forget.

RANDY: OK.

TOM: So, Spray & Forget also has the ability to stop mold and mildew and lichen and algae. And it may be just enough to stop the growth of weeds between wooden deck boards. But you can find that at home centers nationwide. It’s a great product and it has sort of a residual effect.

Now, it’s not an instant-gratification kind of deal. You spray it on there and you let the sun and the wind and the rain get to it. And very slowly, over time, it breaks down all of those materials and stops it from coming back. So, you’re going to have to do something like that to try to maintain this.

RANDY: OK.

TOM: But in terms of stopping the material from getting in between the cracks, that I don’t have a solution for you on, OK?

RANDY: OK. Alright, sir.

TOM: Alright. Good luck. Thanks so much for that call.