Kale is a popular leafy green vegetable known for its nutritional density and adaptability to various climates. From a small, compact rosette to a towering stalk, the ultimate size of a kale plant is determined by a combination of its genetic blueprint and the specific environmental conditions it experiences throughout its life. Understanding these factors allows growers to anticipate and manage the final size of their plants.
Genetic Potential: Mature Size Differences by Variety
The specific variety of seed planted sets the plant’s maximum potential for height and spread. Different cultivars have been bred to display distinct growth habits, resulting in three general size categories for mature plants grown under optimal conditions.
Dwarf Varieties
Dwarf varieties, such as Dwarf Siberian, are the most compact, typically reaching a height of less than 20 inches with a spread of up to 24 inches at maturity. This smaller stature makes them suitable for container gardening or tight garden spaces, maintaining a relatively low profile throughout the growing season.
Standard Varieties
Standard kale varieties, including the popular Red Russian, generally grow between 18 and 36 inches tall, often with a similar spread of 18 to 24 inches. The Red Russian type develops wavy, frilly leaves on stems that begin to elongate as the plant matures.
Tall Varieties
The tallest varieties, like Lacinato (Dinosaur or Tuscan kale), develop a columnar habit. These plants can reach 2 to 4 feet tall. While their height is substantial, the spread of Lacinato varieties tends to be narrower, ranging from 12 to 36 inches, due to their distinctively upright, heavily crinkled leaves.
Maximizing Growth: Environmental Influences on Kale Dimensions
While genetics determine potential, environmental factors dictate whether a kale plant reaches those maximum dimensions. Providing the ideal growing conditions is necessary for encouraging the robust root system that supports a large plant. Three external factors—soil quality, sunlight, and spacing—are particularly influential on the final size of the mature plant.
Soil and Water
Fertile, well-drained soil is a requirement for maximum growth because kale is a heavy feeder that requires abundant nutrients to produce large leaves and tall stalks. The incorporation of organic matter and consistent moisture ensures the plant has the resources needed to sustain rapid vegetative growth. Drought stress can result in stunted growth and bitter-tasting leaves.
Sunlight
Sunlight exposure affects the plant’s density and height. Kale thrives in full sun, which encourages compact, dense leaf growth. However, plants grown in partial shade may experience “legginess,” where they stretch vertically to seek light. This results in a less dense, more spindly structure.
Spacing
Inadequate plant spacing is a leading cause of smaller-than-expected kale plants, as competition for light, water, and nutrients restricts the plant’s ability to develop its full spread. For a plant to reach its full genetic size, a minimum spacing of 12 to 18 inches between plants is recommended, with some larger varieties benefiting from 18 to 24 inches. While tighter spacing can increase the overall yield per area, it results in smaller, less uniform individual plants with reduced leaf dimensions.
Size Management Through Harvesting Practices
Harvesting leaves serves as a management tool that allows gardeners to control the size and shape of the kale plant over the growing season. The choice between two primary harvesting methods directly impacts the plant’s dimensions and longevity. A single, whole-plant harvest is the fastest way to obtain the maximum weight from one plant, but this approach ends the plant’s life.
The preferred method for prolonged production is the cut-and-come-again technique, which involves removing only the oldest, outermost leaves. This harvesting strategy diverts the plant’s energy into fresh, central growth, which results in a bushier, less sprawling plant than one allowed to grow uncut.
As the season progresses, continuous removal of outer leaves causes the main stem to gradually elongate, creating a tall, trunk-like stalk sometimes referred to as a “kale tree.” Although this process increases the plant’s height, the regular removal of leaves limits the overall leaf canopy. Avoid harvesting more than one-third to one-half of the total leaves at any one time.