Gardening for Geeks. Christy Wilhelmi
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 bed? Do you have or anticipate having back problems? Are you a card-carrying neat freak? The answers to these questions will help you determine the size and shape of your beds and how much space to leave between them.
Just How Neat Are You?
Let’s start with the last question first. The “neat freak” bit. It might not seem like a factor in gardening, but it can make the difference between spending time in the garden or not. If you prefer to have everything in its place, but you now have an unorganized and random garden, you probably won’t want to be there very often. A soldierly array of crisp raised beds might just be the ticket. Conversely, if you’d rather your vines ramble, and you love the look of a lush, overgrown jungle, take this into consideration before installing formal square beds. Chances are high that a snaking border or keyhole garden is going to suit you better.
Evenly spaced and orderly is the way to go for some gardeners.
What Do You Want from Your Garden?
Your garden should match your needs. Do you want high production, or do you just want to putter around? If you intend for this garden to produce a bounty of food for your family, you will benefit from structuring the garden with beds in full sun along with easy-to-access pathways with room for a wheelbarrow or large tubs. Build your planter beds wide enough to accommodate large plantings but narrow enough so you can access the produce without stepping into the beds. If, on the other hand, this garden is going to be a place to disappear and putter, then feel free to create cluster gardens, perhaps each with a different theme, and choose locations around your yard to tuck them into. Making choices that satisfy your needs will help you enjoy and use your garden(s) more thoroughly. Let’s look at some pointers for high-production gardens.
High-Production Gardens
Three feet (0.9 m) for kids, more for grown-ups: An adult can reach the center of a raised bed from either side most easily if the bed is no wider than 4 feet (1.2 m). It can be as long as you want—4 feet (1.2 m), 6 feet (1.8 m), 12 feet (3.7 m), or more—as long as you can access the midline of the bed on the two long sides. Some biointensive methods call for beds that are 5 feet (1.5 m) wide. To prevent soil compression that can occur while working these beds, farmers and gardeners usually keep planks of wood on hand to distribute their weight evenly. By laying a plank down across the area, a person can step or kneel on the plank instead of directly on the soil.
Children can’t reach as far as adults and will have to climb into your garden, disturbing the soil and possibly trampling seedlings if they can’t reach the center. Limit kid-sized beds to 4 feet (1.2 m) wide or less. A 3-foot- (0.9-m-) wide bed will be sufficient for adults, while giving children room to grow. A 2-foot- (0.6-m-) wide bed, while it may seem small, can be the perfect size for little hands in a school garden. While we’re on the subject of kids, this is a good time to mention that toddlers are usually pullers or diggers. They love to grab tiny seedlings and get