Arugula is a fast-growing, cool-season leafy green prized for its distinct peppery flavor. Successful cultivation relies on providing the correct amount of space for its growth habit. Optimizing spacing maximizes leaf yield, ensures adequate air circulation to discourage fungal diseases, and regulates the intensity of the spicy taste. Proper management of horizontal and vertical space is fundamental to a productive harvest.
Minimum Spacing for Row Planting
Planting arugula in traditional garden rows is the standard approach when the intention is to harvest the entire mature plant or large bunches of leaves at once. To accommodate the full rosette size of a mature plant, which can span up to 6 inches in diameter, specific spacing is necessary. The initial sowing of seeds should be done in a line, about one-half inch deep, with seeds placed approximately 1 inch apart.
Once the seedlings emerge and reach a height of about 2 inches, a process called thinning must occur to ensure the remaining plants have room to develop fully. For robust growth and to prevent competition for soil nutrients and light, the remaining plants should be spaced 4 to 6 inches apart within the row. Failure to thin seedlings results in overcrowding, leading to stunted plants with smaller leaves and an increased tendency to bolt, which causes the leaves to become excessively bitter.
Spacing between multiple rows is necessary to maintain air circulation around the foliage. Rows should be separated by a distance of 12 to 18 inches. This wider gap ensures that moisture on the leaves dries quickly, preventing common leaf-spot diseases. This minimum spacing focuses on quality and maximizing the size of individual leaves.
Density Management for Continuous Harvesting
An alternative to growing arugula for full-sized plants is the high-density “cut-and-come-again” method, which prioritizes continuous yield. This technique involves planting seeds far more densely than required for mature plants, as the goal is to harvest only small, tender “baby greens.” Seeds can be scattered lightly across a wide planting area or sown in a dense band 2 to 4 inches wide.
For this method, the initial spacing of seeds can be as close as 1 inch apart, or they can simply be broadcast over the prepared soil surface. Since the harvest begins when the leaves are only 2 to 3 inches long, the plants never reach a size where they compete significantly for resources. This higher density capitalizes on the limited horizontal space available in small gardens or raised beds.
Frequent harvesting is a requirement for this dense planting strategy, as it mimics the thinning process and prevents the plants from becoming too crowded. The harvest involves using scissors or shears to snip the outer leaves near the base, leaving the inner growing point, or basal plate, intact to promote regrowth. By consistently removing the oldest leaves, the plant is encouraged to produce new foliage, effectively extending the harvest season and delaying the plant’s natural tendency to bolt in warming weather.
Container and Depth Requirements
When growing arugula in containers, the focus shifts from managing horizontal row space to ensuring adequate soil volume and depth for healthy root development. Arugula has a relatively shallow root system compared to many other vegetables, but it still requires a specific minimum soil depth to thrive. The absolute minimum soil depth for container growth is 6 inches.
A depth of 8 to 12 inches is preferable, as this allows for a larger, more stable reservoir of moisture and nutrients, reducing the frequency of watering and the risk of bolting due to soil dryness. Containers should also be wide enough to accommodate the desired planting density. For a single mature plant, a container with a minimum diameter of 6 inches is appropriate.
If using the higher-density, cut-and-come-again method, a wide, shallow container, such as a window box or a pot at least 10 to 12 inches across, is suitable for multiple plants. Container growing allows the grower to easily move the plants to optimize sunlight exposure or shift them into afternoon shade during high heat. This temperature control delays bolting, prolonging the harvest of mild-flavored leaves.