We have known for years that raised beds offer many advantages over gardening at grade level. They warm up earlier in the spring, the elevated moist soil provides natural energy storage for a greenhouse, and they give us a way to organize plantings. They also provide us with a more comfortable gardening level, and offer good drainage for the plants.
Let's look at how we might go about building raised beds for the plants we choose to grow. There are any number of ways to do it. Choose one that you think is right for you. Consider building a raised bed from:
- Soil. We often don't think of soil as a material for building. Mound up soil in a wide column, and there you have a raised bed. With gentle sloping sides, you can get a 6 to 8 inch raised bed out of just rearranging your soil.
- Wood, the most common material. If untreated, you should line it with strong plastic film to keep the soil from being in constant contact with the wood and rotting it out in a few seasons. Common screw type fasteners work just fine for assembly.
- Composite material. Wood-like in dimension, but made largely from plastics. It doesn't rot and can be assembled just like wood. It is much heavier than wood, but should last a lifetime. This material is expensive too. Use screws, bolts or connecting plates to fasten together.
- Cement blocks. A bit heavy and cumbersome, but allows "a piece at a time" movement and rearrangement of the raised beds. Provides the flexibility of just about any length, width and height. They are also available at reasonable cost since they last a lifetime. No fasteners required.
- Railroad ties, treated timbers or power poles. Heavy and cumbersome, but very strong and long lasting. They need to be lined to keep the treatment away from the soil and you. Can be obtained cheaply, but lining increases their overall cost. Fasteners must be long and heavy, like steel stakes or angle iron.
- Car and truck tires. Not exactly attractive, but useful for making small isolated beds. Black rubber absorbs heat very well to warm up the soil. Useful for growing tubers that need to be covered with soil as they grow -- add another tire and then add more soil. Nothing to fasten. This type of raised bed makes good use of something that is otherwise a waste product.
- Steel or plastic barrels. Good for small isolated beds. Need to be cleaned of potential contaminants. Used whole, they put everything at waist level, but create quite a job if you are the one filling them with soil. Cutting them in half requires special tools or lots of work, but gives a nice 1.5 foot high raised bed. No fasteners required. Can be obtained at no cost.
There you have it. Raised beds offer many benefits, and they can be made from a wide range of materials, each with their own consideration with respect to weight, cost, convenience, appearance and ease of construction.
Consider what you want to accomplish with raised beds, and do some experimentation. I like a raised bed configuration made of half steel barrels. Scrap wood is also a favorite of mine. I use both in an outdoor garden and my first greenhouse. They are light, cost nothing, and provide nice versatility. I also use a large twin raised bed in my second greenhouse made from power poles. It provides high elevated planting beds and serves as foundation for the structure.
Whichever material you choose, the benefits of raised beds will be evident with an earlier season, clearly defined planting areas, better drainage and easier access to your plants. Good luck and good gardening.