How to Garden in Raised Beds

Gardeners who are cursed with poor garden soil will find the raised-bed gardening method to be their salvation. The basic idea is that instead of battling against poor soil conditions, you build above ground, where you have absolute control over the soil texture and ingredients. In a region with extreme soil (very sandy, very clayey, or very infertile), gardeners can tailor the soil in a raised bed, so it is perfect for growing whatever plants they choose.

There are other notable advantages to raised bed gardening. They are excellent for older gardeners or those with physical limitations, for whom tending plants at ground level can be painful or impractical. A garden bed raised even nine to 12 inches above the ground can be much easier to tend, and you can even build elevated, waist-level raised beds that make it possible to garden without ever stooping over at all.

And because the soil in raised beds is exposed on four sides, it warms up earlier in the spring, making for a slightly extended growing season.

When to Garden in Raised Beds

While your actual gardening work will begin at whatever time is appropriate in your region (based on USDA hardiness zone, etc.), the preliminary work can begin months in advance, as you can spend the winter months planning, ordering seeds and other plants, and even cutting lumber in anticipation of speeding along the construction of your raised bed when the weather becomes favorable. In general, though, raised bed gardening begins in earnest about the time the last frost of winter has passed and soil temperatures have reached 60 degrees Fahrenheit or higher. For zone 3 gardeners, this may mean you don't actively begin gardening until June, while zone 9 to 10 gardeners may be able to garden year-round.

In a larger sense, the time to begin raised bed gardening is whenever the advantages of a more accessible garden bed, filled with good-quality, tailor-made soil, become evident to you.

Before Getting Started

A raised bed garden can be best understood as a large, stationary container garden raised up above ground level, sometimes incorporating native soil, sometimes not. Many gardeners choose to fill the entire raised bed with same kind of soilless potting mixture used for portable containers. But if buying large quantities of potting mix (or the ingredients to make your own) is too expensive, you can also fill your raised bed with a mixture of purchased topsoil and organic amendments, such as compost, manure, or peat moss.

Most raised beds include some form of sidewalls to contain the soil. But a raised bed can also be more free-form, with soil and amendments merely piled high over existing soil to make an elevated planting berm.

Contained raised beds are great for vegetable and herb gardens, as well as flower gardens. Fruits, such as strawberries, grapes, blueberries, and raspberries, also do very well in this type of bed. They can even be used to make shrub islands. There are very few plants that won't grow better in a raised bed than they do in an ordinary garden bed.

Choosing a Garden Site

If you know that you'll be growing vegetables or herbs, or sun-loving flowers in your new garden, try to select a site that gets at least eight hours of sun per day—six hours is a bare minimum. A flat, level area is important, and you should also make sure that the area has easy access to water sources, as well as room for you to work.

Planning the Raised Bed Design

When choosing a shape and size for your raised bed, make sure that you'll be able access all parts of the garden without stepping into the bed. One of the main advantages of a raised bed is that the soil doesn't get compacted the way it does in a conventional bed, because it is designed so that you don't have to walk through it.

It is a good idea to keep the garden no more than 4 feet wide, because this way you can access the middle of the bed from either side. If you're placing your bed against a wall or fence that limits access from the back side, then your raised bed should be no more than 3 feet wide. The raised bed can be any length you choose.

Depth for your raised bed should be dictated by the quality of the underlying soil, as well as the plants you are intending to grow. At a minimum, a raised bed should be at least 6 or 8 inches deep—a depth that will support many vegetables, herbs, and bedding plants. At this shallow depth, though, you are counting on underlying soil being of sufficient quality to allow plant roots to extend down below the bed.

If you have decent subsoil (not too clayey or rocky) you can simply loosen the soil with a garden fork and build a 6- to 8-inch deep raised bed. If you have poor subsoil, then a deeper raised bed is a better idea. Many crops, such as carrots, parsnips, or potatoes will do better in beds that are at least 12 inches deep. Deeper beds are also well suited for many woody shrubs and perennials.

Choosing Building Materials

While it's possible to build a raised gardening area by simply heaping additional prepared soil onto the garden site, most raised beds are constructed with some kind of rigid walls for the frame.

You can choose from a variety of materials to construct your frame. Wood is a very popular choice, because it is inexpensive and easy to work with. One advantage of wood is that you can base your raised bed dimensions on standard lengths of framing lumber, which minimizes the amount of cutting required. (Home centers generally sell framing lumber in 8-, 10-, 12-, and 16-foot lengths.)

Concrete blocks, natural stone, or brick are also nice options. Retaining wall blocks, for example, are easy to assemble into secure raised bed walls. Stone and concrete are more expensive options, though, and moving them around requires no small amount of effort.

Some gardeners go the ultra-simple route and simply place bales of hay or straw in whatever configuration they desire, then fill it with good soil and compost and plant it up. This solution will only give you a year or so of use because the straw will decompose. But it's worth trying if you don't mind replacing the bales yearly, or if you're still developing a more permanent solution.

Our demonstration shows how to build a raised bed from standard cedar dimension lumber.