Can you recommend a nontoxic waterproof wood sealer for my outdoor window boxes?

Matthew Bremer, AIA, is principal of Architecture in Formation PC, a young, award-winning architecture and design firm based in New York. He is involved with designing and developing The Ranch Commons, a sustainable community near San Antonio, Texas.

Question: I'm building and planting my own outdoor window boxes this year, and I'm having a hard time finding a nontoxic waterproof wood sealer that won't poison my plants or the environment, and that doesn't need to be reapplied every year. Any advice?

– Sam Beck, Brooklyn, NY

Answer: While you're right that you still have to search hard among conventional wood sealers to find a healthy alternative, that is changing. There’s no need to subject yourself and others to toxic chemicals, or to poison your plants as they begin to grow. Eco Safety Products offers a series of LEED-compatible nontoxic, low-odor, low-to-zero-VOC sealers, made mostly from soy. AFM Naturals offers other products, as does SoyClean.

Reviews often point out that these products are not as durable and long-lasting as traditional sealers, and that they are hard to apply and costly, but with only planter boxes to cover, rather than a deck or fence, any of these products should serve you well.

GreenHomeGuide's Ask A Pro archive has answers to dozens of other green home questions from our network of the best and brightest green architects, designers, contractors and consultants across the U.S.