Q. We tore out the grass in our front yard this spring to put in an organic garden, but as winter approaches, my husband and I are looking at our bright new wooden fence and wondering how we can seal it to keep it looking great for years to come. But spraying on a chemical sealant around our lush, chemical-free foodstuffs seems like a horrible idea. Any ideas?

Kalyn B.
Seattle, Wa.

A. Dearest Kalyn,

Swapping a patch of boring old lawn for a sprouting wonderland of produce? Talk about a home upgrade. Nothing against grass, per se, but it doesn’t taste nearly as good on my salads.

Now that you and your garden are in it for the long haul, it’s understandable that you’d want your lovely new fence to come along for the ride. After all, failing to protect it from the battering power of the sun and rain, plus the decaying power of fungi and mildew, means you might have to replace it much more frequently — an unnecessary waste of trees.

But you’re right to wonder about the safety of the stuff we use to shield fences (and decks, for that matter) from the elements, Kalyn. No question: Some paints, stains, and sealers contain nasty ingredients. (I’m assuming that your fence is not built from pressure-treated wood, which opens up a whole ‘nother can of worms when we’re talking garden use.)

So before we wade into that chemical soup, I have to ask: Do you really need to treat your fence? If you’ve chosen naturally rot-resistant cedar or redwood to build it, then you might not have to do a thing. Going for these ultra-hardy woods (sustainably harvested, of course) is one of the best ways to skip problematic sealants and water repellents altogether.

No luck? Then deciding how you want your fence to look is a useful jumping-off point. From there, you can research the least toxic way to achieve your goal. Paint provides a surface layer of protection from UV damage and obviously changes the color of the wood (matching pickets and window sills, anyone?), but is tougher to maintain. Stains penetrate deeply into the wood and often also serve as water-repelling sealants; transparency varies, with tinted types providing more UV protection but also obscuring the wood’s natural hue. Head over here for a lot more food for thought on your choices.

Once you have a vision in mind, you’ll need to start doing your research, Kalyn. With both paints and stains, we’re primarily concerned with volatile organic compounds — these villainous VOCs are at best noxious and headache-inducing, and at worst, cancer-causing. This is mainly an issue with oil-based paints and stains, which are also highly flammable, require toxic thinners to clean up, and need to be treated as hazardous waste.

There’s also this twist: Oil-based products can actually encourage mildew growth, so some include added fungicides and mildewcides. Considering your fence’s proximity to next year’s tomatoes, experts advise caution: “We don’t recommend using biocides on anything used in a garden,” says Erika Schreder, science director at the Washington Toxics Coalition.

Some argue the solvents in oil-based products penetrate more deeply into the wood, making them longer-lasting and more durable than less-toxic alternatives. Low- or zero-VOC water-based products keep getting better, however, and can serve with distinction on your fence. I’d do as the EPA suggests and lean toward water-based formulas, checking reviews and Consumer Reports as you shop.

Manufacturers don’t always make shopping easy, by the way, so you might have to do some digging when comparing options. Schreder has a few more bits of advice for you: “The first step is finding a [company] that’s willing to disclose all its ingredients,” she says. “Generally, you want to start with a company that markets itself as a safer alternative.” From there, you can check out the product’s material safety data sheet (MSDS), usually available on the company’s website, for more information on the safety of said ingredients. Local green-building stores can be a great help as you look around, too.

Finally, I should mention a few other options. Some people swear by treating exterior wood with still more natural products, such as linseed oil or milk paint. I don’t have any experience with these alternatives, so I can’t weigh in, but you may find them worthy of investigation, Kalyn. Good luck, and here’s to a rain-shedding, sun-blocking, gracefully aging fence for years to come.

Semitransparently,
Umbra