Safe Protective Coating for Planter Boxes

Oil

• Natural finishes such linseed oil or tung oil are good choices to protect your wood planter, especially if you want the wood grain to show. Both are nontoxic and make the wood water-resistant. Oil-varnish combinations such as Nordic oil or teak oil are also options. Simply rub the oil onto the wood with a rag. Repeated applications are needed to ensure adequate moisture protection. Clean the planter boxes and reapply the oil finish annually.

Varnish

• Try varnish for a more durable and longer-lasting finish. Varnishes typically are a combination of linseed or tung oil, a resin such as polyurethane and a solvent such as mineral spirits or paint thinner. "Spar," or marine-grade varnishes, are designed for exterior use in moist conditions and include a UV protectant. Water-based acrylic varnishes are also available, which are less toxic to handle and easier to clean up, and emit lower VOC (volatile organic compound) levels.

Paint

• Coating your planters with exterior house paint allows you to match them to the color of your house for a unified appearance. You have a choice between acrylic latex paint and oil-based paint. Latex paint dries faster, is easier to clean up and emits fewer toxic fumes than oil-based paint. Oil-based paints form a durable surface against abrasion, but they degrade more quickly in sunlight. Always apply one or two coats of primer before painting.

Other Alternatives

• If you have not yet built or purchased your planter boxes, consider using naturally rot-resistant or treated woods. Wood treated with chromated copper arsenate (CCA) is widely available and lasts for many years without any additional protective coating. Do not use treated wood for planters that will contain food crops; instead, use decay-resistant woods such as cedar, redwood, teak or cypress. Another method of protecting your planter is to use a plastic liner to prevent soil from coming in contact with the wood.