further reduce the need to weed.
Raised beds are the method of choice for most biointensive gardening methods (more about those in Chapter 5) because they concentrate resources and allow a gardener to maintain the beds without walking on and compressing the soil. Raised beds are also handy for folks with lower back issues or certain disabilities. The elevated surface area makes it easier to garden without bending over as far, and often you can even build beds tall enough to prevent bending altogether. Elevated raised beds (up on legs) can be built for wheelchair accessibility. If you have trees or hedges near your garden area, you can line your raised beds on the bottom to prevent thirsty tree roots from taking over your garden. See? The benefits really do go on and on.
Vegetable garden beds don’t have to be boring.
Materials for Raised Beds
When it comes to deciding what materials to use for building a raised bed, you have a lot of options, depending on your budget and needs. If you strive to recycle and reuse found materials, then “urbanite” or broken concrete might be the way to go. If you’re in a tight space, thinner materials that allow for the most gardening area with the least bulk—wood or composite lumber—are better choices. Let’s take a look at the possibilities.
Wood
Wooden raised beds can be assembled quickly and last for years, depending on the type of wood you use. Douglas fir, which is relatively inexpensive, lasts about three to five years before it begins to decompose (though it can, in some circumstances, last for more than ten years in dry conditions). If you are building a simple frame for an experimental garden, or you plan to move in a few years, Douglas fir is good enough to use.
Redwood is a more durable option for wood-framed raised beds. It is an acidic wood, which makes it naturally antimicrobial. Redwood raised beds tend to last about ten to fifteen years longer than Douglas fir beds.
Cedar, which lasts twenty years or more, is a great option for long-term raised beds. It can be more expensive but is worth the investment if you plan to be in the same place for a while. Cedar resists decay and is often available as rough-cut lumber, which means it hasn’t been milled down to the standard (think thinner) dimensions. The thicker wood is more rustic, but those extra millimeters make it even more durable.
Composite Lumber
Composite lumber is another option for planter beds. This type of material is a blend of recycled plastic packaging waste and wood pulp. It is extruded into the shape of wood and is usually used to build decks and patios. Many companies offer prefabricated raised beds made from nonleaching and soil-safe composite lumber, but be aware that not all composite lumber products are safe for direct soil contact. Trex® decking, made by Trex Company (trex.com), is one of the few composite lumbers that specifically states that it is safe for direct soil contact. Some composite lumbers begin to disintegrate when they come into contact with soil. Veranda®, a thinner composite product found on the shelves of larger hardware stores, clearly states that it is not safe for direct soil contact.
A raised bed made from two levels of 2- x 6-inch (5- x 15-cm) Trex decking. With no known gophers in the neighborhood, we used chicken wire simply as a precaution. In the end, it was not necessary.
Composite lumber has its advantages. It is long lasting (Trex is guaranteed for twenty-five years but is likely to last even longer), it won’t splinter, and you never need to paint or stain it. The material costs about a third more than wood, but, given its durability, it’s worth the expense to know that you won’t have to build another raised bed for a very long time, if ever again. Composites are dense and heavy, so you may blow through a saw blade or two while cutting it, but in all other respects it cuts and behaves like wood.
Geeky Gardening TiP:
A Word about Redwood
Redwood is often sprayed with a solvent to aid the curing process. It takes a long time to dry redwood naturally, and milling companies have found that by spraying the wood with acetone or methanol, they are able to cure and dry redwood more quickly. While there is a process for removing the solvents after drying is complete, traces of these chemicals have been found in the wood and can leach into the soil. Ask your lumberyard professional to verify whether the wood has been solvent-dried or kiln-dried. You can often special-order kiln-dried redwood for your project.
Urbanite or Concrete Blocks
These are popular options for those who are looking to use recycled products. If you spy your neighbors breaking up their concrete driveway or sidewalk, ask if you can have the broken pieces. These concrete bits are great for building retaining walls that are thick and sturdy. They can also be used as paving material for pathways. If you decide to use urbanite to build a raised bed, however, be aware that it is usually 4 to 6 inches (10 to 15 cm) thick and can be cumbersome to climb over when reaching into a planting area. As mentioned before, wood offers the thinnest option for a raised bed, usually just 2 inches (5 cm) thick. Blocks take up a lot more room, so if growing space is at a premium in your yard, opt for something thinner. That said, if you are looking to make raised beds that appear earthbound, solid, and hefty, urbanite or concrete blocks can create this look.
Cinder Block
Cinder block, like urbanite, is a substantial building material for raised beds. Unlike concrete, though, cinder block is made with fly ash, a waste product of the coal industry. While there is no official study proving this, it is speculated that heavy metals present in fly ash—namely arsenic, cobalt, lead, and mercury—will off-gas and leach into groundwater and soil. Gardening forums have countless discussions on this subject, with healthy arguments both for and against the use of cinder block, but it deserves further investigation if you plan to use this material.
Wooden posts and stones create a vegetable garden with Japanese overtones.
Stones and Other Natural Materials
If you plan to grow mostly in-ground but still want to include some decorative elements of design along with a few extra inches of garden soil, stones or other natural materials offer a lot of flexibility. No mortar is necessary unless you are building borders that are several layers high.
Cob and Adobe
These earthen materials are used to build houses, retaining walls, and other structures. Both use a mixture of sand, clay, and straw to form whatever shape is desired. To make these structures durable as raised beds, and able to withstand constant moisture and soil contact, lime is added to a finishing plaster as a sealant. Alternatively, adobe bricks are often found in gardens designed using permaculture principles and are an acceptable material for raised beds. Earthbags are another earth-based building material, often made from otherwise discarded, misprinted polypropylene bags. They simplify the building process: rather than making adobe bricks, you fill the earthbags with native soil (with as little as 5 percent clay) and stack them together. Earthbags can then be covered with a layer of adobe for a smooth finish. Some earthbag aficionados suggest coating the soil side of the new retaining wall with a layer of cement-based stucco plaster to help prevent degradation from excessive moisture.
Guidelines for Shape and Size
When building your garden beds, there are several other things to take into consideration. Will you have small children in the garden with you? Do you want to bring a wheelbarrow right up to a raised
