Once, when you wanted to build a raised bed, you might have used new or recycled sleepers. But many landscapers and gardeners no longer use sleepers because the preservatives in them can bleed into the soil and damage plants. Instead, there are a wide range of wood choices that you can purchase for your raised bed.
Not long ago, redwood was a no-no for building projects because the wood was harvested from shrinking redwood forests. But today, redwood harvested from newer redwood seedlings is a sustainable resource. Redwood is a wood of choice for outdoor building projects such as decks and fencing due to the wood's ability to resist weathering and decomposition. Because redwood is naturally resistant to weathering, it is not treated with chemicals that can harm the soil. Choose heartwood when selecting redwood lumber. Sapwood, which comes from near the tree's outer layers, will decompose more quickly when exposed to moisture. Instead select kiln-dried heartwood.
Cedar has long been a popular building material, not only for decks and fencing but also for furnishings and storage. The wood is naturally rot resistant and has a pleasant odour that will repel pests. Like redwood, cedar's rot-resistant properties mean that it is not treated with chemicals that can harm the soil. Cedar is a more sustainable resource than redwood because it matures more rapidly. And it can be harvested more quickly and easily than redwood. As with redwood, avoid sapwood and select kiln-dried heartwood.
Ipe, which is manufactured in the names Ironwood and Pau Lope, is a tropical wood that was introduced to the American market very recently for deck construction. Ironwood is twice as dense and durable as teak, and will sink in water. It has an olive colour and a slightly oily appearance. The wood has few splinters to create surfaces that are subject to mildew or rot. Ipe used in decks is guaranteed for 20 years if treated a single time.