Square Foot Gardening (SFG), a method popularized by Mel Bartholomew, offers a systematic approach to maximizing vegetable yields within limited space. It fundamentally shifts the focus from traditional, long rows to small, intensive planting areas, most often raised beds divided into one-foot squares. This technique is designed to simplify the gardening process, reduce labor, and conserve resources like water and seed. The success of SFG relies on standardized planting density rules that determine precisely how many plants can thrive in each square foot section. These rules allow gardeners to plant much closer than they would in a conventional garden, creating a dense canopy that helps suppress weed growth.
The Four Density Categories
The foundation of the SFG method is its four density categories, which dictate plant count based on the crop’s mature size. Instead of relying on complex row and plant spacing measurements, the system uses simple square numbers: 16, 9, 4, or 1 plant per square foot. This standardization simplifies the planning process, allowing gardeners to easily visualize and execute their layout.
The categories correspond to the amount of space a plant needs to fully mature without competing for light, nutrients, or air circulation. Small crops, requiring approximately three inches of space, are planted 16 per square. Medium crops, needing four inches of space, are planted nine per square, while large crops requiring six inches of space are planted four per square. The final category is reserved for extra-large or sprawling plants that demand the entire 12-inch square for a single specimen.
Planting Guide for Small and Medium Crops
The most intensive planting densities fall within the small and medium crop categories, utilizing the 16- and 9-per-square counts. Plants that mature quickly and remain small, such as radishes and green onions, are ideally suited for the 16-per-square density. This density is achieved by planting four plants along each side of the square, resulting in a three-inch spacing between each specimen. Carrots and parsnips are also commonly planted at this density.
Crops falling into the medium-sized category, which require four inches of space, are planted nine per square foot. This group includes bush beans, beets, turnips, and spinach, which need slightly more room to develop their root structures or foliage. Nine beet seeds can be planted in a square, with the goal of harvesting medium-sized roots. Precise placement is achieved by dividing the square into a three-by-three grid for these crops.
The next density level is four plants per square, designed for larger leafy greens and small bulb crops that require a six-inch spacing. Examples include Swiss chard, leaf lettuce, and large onion varieties, which need the extra room to form a substantial head or bulb. This six-inch spacing ensures sufficient airflow around the developing foliage, which is important to mitigate the risk of fungal diseases.
Managing Single-Plant Crops and Vertical Growth
The final density category is one plant per square foot, which applies to crops that grow very large, spread widely, or have extensive root systems. This group includes extra-large plants like broccoli, cauliflower, cabbage, and kale, all of which require 12 inches of space to form their mature structure. Solanaceous crops, such as tomatoes, peppers, and eggplant, also fall into the one-per-square category due to their mature size and need for robust support.
Many plants in the single-plant category are vining varieties, including cucumbers, melons, and certain squash types. To prevent these sprawling crops from consuming the limited horizontal space in the garden bed, the SFG method mandates the use of vertical supports. Trellises, cages, or A-frames are integrated directly into the system, allowing vining crops to grow upward along the grid structure.
This vertical growth strategy is essential to maximize the efficiency of the garden, transforming two-dimensional space into three-dimensional growing area. When placing these vertical supports, it is recommended to position them along the north side of the raised bed. This strategic placement ensures that the tall, vining plants do not cast shade over the shorter, sun-loving crops planted at higher densities in the squares to the south.