A raised bed is a contained structure, typically made of wood or metal, that sits above the native ground level, offering a defined and controlled growing environment. This gardening method provides significant advantages, including superior control over the soil medium and reduced physical strain from bending. Since the structure separates the garden from the surrounding soil, it allows for a highly customized approach to cultivation. Selecting the right plants is paramount to capitalizing on the benefits of this unique space, prioritizing those that offer the most abundant harvests.
Preparing the Growing Medium
The success of a raised bed hinges on the quality of its contained soil, which must be built from scratch rather than relying on existing earth. An ideal growing medium is constructed by blending components that address nutrition, water retention, and aeration. A practical blend utilizes a ratio of approximately 50 percent topsoil, 30 percent compost, and 20 percent aeration components like perlite or vermiculite.
Topsoil acts as the primary filler and provides the necessary structure for roots to anchor. Compost introduces the organic matter and rich microbial life that feeds the plants. The addition of perlite or coarse vermiculite is important for creating pore spaces, ensuring proper drainage and allowing oxygen to reach the root systems.
Before adding this custom soil blend, the bottom of the bed should be lined with a permeable layer, such as cardboard or landscape fabric. This suppresses weeds and prevents the new medium from mixing with the native soil beneath. This construction creates a loose, fertile medium ideal for plants that struggle in compacted gardens.
Top Choices for Maximizing Yield
The controlled environment of a raised bed is perfectly suited for plants that benefit from loose soil and intensive planting techniques. Root crops are especially productive because the custom medium prevents the compaction that often stunts their growth in traditional gardens. Vegetables like carrots and radishes thrive in this deep, friable soil, allowing them to be planted much closer together than traditional seed packet instructions recommend. Carrots can be spaced as tightly as three to four inches apart, while beets require slightly more room at around six inches between plants for proper bulb development.
The ability to plant intensively dramatically increases the yield of crops such as leafy greens and bush varieties. Biointensive planting methods space plants so their mature leaves touch, which helps shade out weeds and conserves soil moisture. Compact plants like spinach and loose-leaf lettuce can be planted with as little as six inches between them, compared to the wider row spacing required in field gardening. Bush varieties of beans also maximize space by avoiding the sprawl of pole beans, and can be spaced approximately eight inches apart, allowing for a dense block of production.
Vertical growing is another technique that leverages the height of the bed to save horizontal space. Crops such as cucumbers, pole beans, and small determinate tomato varieties are trained upward on a trellis or cage installed within the bed. By utilizing vertical supports, a single square foot of bed space can support a plant that would otherwise occupy multiple square feet of ground area. This strategic use of the third dimension ensures that the limited, high-quality soil is dedicated primarily to root development and harvestable material.
Vegetables That Waste Space
While nearly any vegetable can technically be grown in a raised bed, some are inefficient and consume a disproportionate amount of space relative to their yield. Large, sprawling vine crops, such as full-sized pumpkins and certain winter squash, are particularly inefficient choices for the contained environment. A single vine can easily grow up to 30 feet long, requiring nine or more square feet of space and often spilling over the edges of the bed.
These massive plants provide a low yield per square foot compared to the investment made in the custom soil. Full-size zucchini plants, while highly productive, develop a massive canopy that shades out neighboring plants, reducing the potential for a dense, mixed planting. For those who wish to grow these types of vegetables, miniature or bush varieties are a more suitable choice for maximizing the premium space.
Corn is another plant that is inefficient in a standard raised bed due to its low yield per plant and its height. Corn requires planting in tight blocks for adequate wind-pollination, and its tall stalks can shade smaller, sun-loving plants nearby. Furthermore, growing full-size potatoes requires hilling dirt around the stems, which consumes a vast amount of the premium soil medium. The space required for a large potato harvest is often better allocated to smaller, more continuously productive root vegetables.