Mulch Tests: Rubber stacks up well against wood

Rubber mulch might sound as aesthetically appealing as an artificial Christmas tree, but it does have a few selling points. It can eliminate the need for annual mulching, since rubber doesn’t break down as wood does; it’s heavy enough to stay put; and you can use less of it to control weeds—you need about 1.5 inches of rubber mulch compared with about 3 inches of wood mulch. But when ignited by an open flame, rubber mulch burns hotter than wood mulch and the fire is harder to put out.

We tested RubberStuff Landscape mulch (left in photo; sold online and at some Home Depot stores), Dupont Garden Products Long-lasting mulch (center in photo; sold at Lowe’s) and red-cedar wood mulch (right in photo). Here’s how they fared:

Weed control. Rubber and wood did about equally well. No weeds grew through, though some crept up around the edges.

Staying power. We flooded all three mulches with an open hose. The wood rose up and floated off; the rubber remained. RubberStuff also claims not to blow away. When we held a leaf blower set on high 2 to 3 feet from the wood mulch, it flew all over the place. When we ran the same test of the rubber mulches, the Dupont blew around a little and RubberStuff didn’t budge.

Weathering. We set up trays of the mulches on the roof of our headquarters, covered part of each, and left the rest open to the elements. After 32 weeks, the wood and the Dupont had faded slightly; the RubberStuff had not. Manufacturers indicate that the color will last more than 10 years, but our tests suggest that some fading could occur.

Flammability. We placed a burning cigarette into a tray of each of the mulches and a lighted match into a tray of each. The cigarettes did not start a fire, but the matches did. The rubber mulches burned faster and hotter, creating a more severe fire that was harder to put out than the one in the wood mulch.

The bottom line. Rubber mulch won’t provide soil with organic material but will control weeds, and you don’t need to replace it as often as wood. Rubber could be a sensible choice, especially around trees and perennials, and either Dupont or RubberStuff should perform fine. Dupont costs about $13.75 per cubic foot and RubberStuff about $15. Wood costs about $1.50 per cubic foot.

While our tests did find very low levels of lead in rubber mulch, the levels were comparable to or lower than levels in soil around homes. Note that rubber mulch isn’t suitable for playgrounds or play areas: It might contain small pieces of steel or nylon. Its flammability also makes it a questionable choice for homes with smokers or in areas that get frequent fire-weather watches or red-flag warnings. Environmental groups and state governments are also conducting studies to determine whether chemicals in rubber mulch leach into soil.

Comments

[Scott Diehl]

What is going on here?

I don't get this article.

I thought Consumers Union was here to protect me?

Oh sure, it doesn't do anything but block weeds...

oh and it will burn your house down...

but don't worry about spreading it around your YARD.

It is the sensible choice...afterall.

This person who wrote this should be FIRED.

Rubber mulch? That's ABSURD. Now they have a spreading their recycled rubber bits onto our yards as MULCH!

Who do you think we are? Oh...wait...the moron masses. I get it.

Give me a break!

[Donna Rae]

-Wood mulch can carry insects which will attack the wood components of your home.
-Wood mulch will burn.
-Wood mulch is produced by cutting down and grinding up trees, which store carbon dioxide, produce cleaner air, moderate temperature extremes, fight erosion, etc.

-Rubber mulch uses material that is otherwise dumped into landfills or stored in huge piles which can in bulk produce huge and horribly smoky, smoldering fires.

Question-Keep the trees or kill the trees?

Question-Store the waste rubber in small layers as a useful landscape tool, or let the old tires pile up by the acres and risk toxic fumes from large fires?

Answer: Environmentally, I'd choose rubber mulch. If I want something to enrich my soil, I can use compost, which is far better for the job than wood mulch.

Answer: For the above reasons and convenience, I choose rubber mulch for preventing erosion around the three foot strip nearest my house, where plantings causes poor air circulation and mildewy odors.

Longer-term Plan: For my garden beds on the rest of our lot, I'll probably phase in rubber mulch around the edges and as fill, but keep 24" of wood chips around the base of annuals, perennials, shrubs and trees. We have sandy soil, and the wood chips help prevent stress on the plants from dried out ground and will limit the need for sprinkling.

Just my opinion.

[Allison]

Educated consumers choose to put these products down, knowing that they not only help our planet, but will last for at least 15 years. That is 15 years of never having to add mulch chips into your planting beds, saving a tremendous amount of money, since most people re-mulch every year. Additionally, the mulch allows water and fertizer to penetrate faster and easier to roots, conserving water and saving you money.The smarter and more responsible choice is rubber mulch. FYI - Rubberstuff has the longest warranty. I looked it up.

[Lynette Corn]

I'm thinking of using this as a border along the sides of my driveway where my kids make ruts with their vehicles. Is this possible or will it get knocked all over the yard? I also have some Japanese knot weed growing along a stream in the backyard I haven't been able to get rid of. If I use this product along the sloping sides, will it stay put and prevent the weeds from growing back?

[Meredith]

Has anyone actually USED this in their home landscaping? It sounds great for my yard because years of previous owner's avid mulching has raised the ground level higher than it should be and we have drainage/grading problems. Adding a thin layer that doesn't need to be replaced is very attractive. Plus I like that it doesn't retain water like wood would. I'd love to hear how fall leaf raking and other bed maintenance activities work in real life - if anyone has experience - thanks!