Raising the Bar
Getting Started with Raised Garden Beds
Raise gardening to a new level with raised beds—above ground growing containers that are open to the ground underneath. The benefits are many.
If your property has adverse soil conditions such as poor drainage, low fertility, or poor soil structure, rise above the problem by building a raised bed filled with rich soil. Tired of weeding on your hands and knees? Build a bed with a wide rim that’s high enough to sit comfortably on the edge while you’re tending to the plants. Open the possibility of gardening to people in wheelchairs with beds build at an appropriate height.
A raised bed helps you concentrate and focus your water usage to exactly where it should be, thus reducing weeds. They also reduce the possibility of compacting the soil or damaging plants due to walking in the growing area. To provide access to the plants without the need to walk in the bed, make it narrow enough (about four feet) to reach at least halfway across from either side.
If you’re building a raised bed next to a garden living space, such as a patio or terrace, build it in a style and out of materials that complement the surrounding structures so the look is unified and harmonious. In more utilitarian areas, such as a remote vegetable or cutting garden, wood or composite plastic materials are the most common building materials.
Gardeners are spoilt for choice when it comes to materials for building raised beds. Review the following three main materials and the pros and cons of each before embarking on your new garden design.
Rot-resistant woods such as cedar (Eastern White or Western Red), redwood, and cypress contain natural chemicals that make them resistant to decay. These woods are an attractive, natural material; however, even rot-resistant wood eventually will degrade. The lifespan will depend on the type of wood and climate. Wood lasts longer where the air is dry and rots quickly in rainy regions.
If you opt for wood, make sure it is old-growth or second growth. Sapwood (milky white outer wood) will quickly rot. Do not use chemically treated lumber, particularly if you plan to grow food. The toxic preservative materials leach out of the wood, potentially contaminating the soil and the plants growing in it.
RECYCLED PLASTIC (HIGH-DENSITY POLYETHYLENE)
HDPE (High-density polyethylene) is a long-lasting material typically guaranteed for a minimum of fifty years. It is a stable material so the chemicals do not leach, and it is resistant to cracking, chipping, and freeze-thaw cycles. The boards do not shrink, warp, or expand over time, although the linear strength is less than wood, so long lengths need more cross-bracing.
The recyclable material comes in a choice of fade-resistant colors. The major negative is the cost, which is high; however, if amortized over decades, it ultimately costs less than wood, which will need replacing much sooner.
COMPOSITE WOOD (BLEND OF WOOD FIBER AND UV-PROTECTED RECYCLED POLYPROPYLENE)
Because they are joined with screws, composite woods are easy to assemble. The printed wood grain pattern conveys a quasi-natural look; nothing in nature repeats so uniformly. The material is weather and rot resistant, and the joint system with straight and curved sections allows for enlarging beds and for shape flexibility, including circles and ovals.
The hollow boards can easily be damaged, and tall and long beds are likely to bow outward. In addition, the color is less stable than the HDPE material, fading in just a few years.
Whether built of wood, plastic, brick, stone, or other building materials, raised beds can add immeasurable value to your gardening pleasure and success.
Best Soil for Raised Beds
There is no one-size-fits-all soil for raised-bed gardening. Some plants, such as blueberries, require acidic soil; others prefer a neutral or alkaline base. In an arid climate you will want a mix that retains moisture; in wetter parts of the country, a good draining soil is best. The beauty of a raised bed is that you can custom-tailor your soil to the plants’ needs.
A good, all-purpose raised bed soil is a well-blended mix of 50 percent each topsoil and compost. Be sure of the quality of both ingredients. Some companies will deliver dirt taken from the top layer of the ground and call it topsoil. Do your research before you place an order.
Written by CATRIONA TUDOR ERLER
As featured in Home By Design® Magazine