Elevated garden beds (EGBs) have become a widely adopted method for growing food, offering gardeners a manageable space for cultivation. This technique allows for better control over soil quality and drainage compared to traditional in-ground planting. Choosing the right crops, however, depends on understanding the unique, contained environment of these raised structures. This guide provides insight into selecting plants that will thrive within the defined constraints of a framed bed.
Foundational Planting Considerations for Elevated Beds
The primary consideration for any elevated garden bed is the constraint of soil depth, which dictates the maximum size of a plant’s root system. Most vegetable roots require a minimum of 6 to 8 inches of soil for healthy growth, but deeper beds of 12 to 18 inches are necessary to accommodate larger produce. Since the soil volume is finite, it must be a lightweight, high-quality mixture designed for containers, not compacted native garden soil.
Elevated beds naturally promote superior drainage, which is generally beneficial for preventing root rot but also means the soil dries out much faster. This accelerated moisture loss requires more attentive watering than an in-ground garden, especially during warmer months. Understanding these factors is necessary before selecting any seeds or seedlings for the bed.
Optimal Choices for Shallow and Medium Depth Beds
Plants with shallow root systems are the most productive choices for beds 6 to 8 inches deep. Leafy greens like loose-leaf lettuce, spinach, and arugula thrive in this limited space and can be harvested using the “cut-and-come-again” method for continuous yield. Most culinary herbs also flourish in these shallower conditions, as they appreciate the well-drained soil.
- Basil
- Thyme
- Mint
- Oregano
For beds ranging from 10 to 14 inches deep, gardeners can successfully cultivate plants with more extensive root systems and those grown for their roots or fruits. Root vegetables like radishes, beets, and shorter carrot varieties develop well in the loose, obstruction-free medium. This depth is also sufficient for fruiting plants such as bush beans, smaller pepper varieties, and compact eggplant types.
The improved environment of an elevated bed is well-suited for specific compact cultivars, such as ‘Patio Princess’ tomatoes or ‘Eight Ball’ zucchini. These medium-depth beds provide enough volume for the root systems of these plants to access the necessary nutrients and water. Pole beans are also an excellent choice, as they utilize vertical space while only requiring a moderate root depth.
Plants to Avoid Due to Root Development Needs
Certain popular crops should be avoided in standard elevated beds due to their deep root requirements or excessive size. Large, indeterminate tomato varieties, for example, require 18 to 24 inches of soil depth to support their extensive root structure and vigorous growth. Planting them in a shallower bed often results in stunted growth and a reduced harvest.
Perennial crops like asparagus and rhubarb are not suitable because they develop complex root systems that can reach several feet deep over their long lifespan. These plants demand permanent, dedicated space and will not perform optimally when their roots are restricted.
Furthermore, large sprawling vegetables, such as full-sized winter squash and melons, will quickly dominate the limited surface area of a raised bed, crowding out neighboring plants. Corn also presents a challenge because its height and wind-pollination needs require a large block of space rather than a confined row in a bed. Focusing on compact, annual varieties preserves the limited soil volume and nutrient reserves for crops that excel in a contained setting.
Techniques for Maximizing Elevated Bed Yield
To achieve maximum productivity within the small footprint of an elevated bed, strategic planting and layout are necessary. Intensive planting places plants closer together than traditional row gardening, maximizing the use of every square inch of the bed’s surface area. This is effective because the soil in a contained bed is richer and more consistently amended.
Succession planting involves immediately replacing harvested crops with new seeds or transplants. For instance, after harvesting a spring crop of radishes, a gardener can immediately sow a heat-tolerant variety of bush bean in the same space. This careful timing prevents the soil from sitting fallow and improves the overall yield from the bed.
Utilizing vertical space is another technique for increasing the harvest without increasing the bed’s footprint. Installing trellises, cages, or obelisks allows vining crops like cucumbers, peas, and pole beans to grow upward. Growing vertically saves valuable horizontal space and improves air circulation around the plants, which can help reduce disease pressure.