Kale is a highly nutritious, leafy green vegetable that thrives in cooler temperatures, making it a favorite for home gardens. Growing this resilient brassica from seed is a practical approach that offers significant cost savings compared to purchasing transplants. Starting with seeds also grants access to a wider selection of heirloom and specialty varieties not typically found in garden centers. This method provides the foundational control needed to cultivate a healthy, productive crop.
Determining Optimal Planting Time and Location
Kale is a cool-season crop, performing best when temperatures are between 55 and 75 degrees Fahrenheit. Plan for two main planting windows: early spring, about four to six weeks before the last expected frost date, and late summer for a fall harvest. Fall planting is often preferred because cooler autumn temperatures enhance the sweetness and flavor of the leaves.
Selecting the right location is important; kale prefers full sun (six or more hours of direct sunlight daily). However, in regions with hot summers, afternoon partial shade can prevent bolting, which causes the plant to prematurely flower and the leaves to turn bitter. Good soil drainage is paramount, as waterlogged roots can quickly lead to disease and rot.
The ideal soil pH for kale is slightly acidic to neutral (6.0 to 7.0). Before sowing, thoroughly prepare the area by incorporating a generous amount of well-aged compost or other organic matter into the top six inches of soil. This amendment improves the soil’s structure, enhances water retention, and provides a slow-release source of nutrients.
Sowing Seeds Indoors or Direct Sowing
Starting kale seeds indoors provides a head start on the growing season, especially for an early spring crop. Sow seeds approximately eight to ten weeks before the last expected spring frost date in individual containers or cell trays filled with a sterile seed-starting mix. Containers should be at least two inches deep to allow for adequate root development before transplanting.
Plant seeds at a shallow depth of about one-quarter to one-half inch. After sowing, place the containers in a warm location, ideally around 70 degrees Fahrenheit, until germination occurs (usually five to eight days). Once seedlings emerge, they require strong light from a south-facing window or a grow light to prevent them from becoming leggy and weak.
Direct sowing is a simpler method, suitable for fall crops or when the danger of a hard frost has passed in the spring. When planting directly into the garden bed, sow seeds about a quarter-inch deep and space them approximately three to four inches apart initially. This close spacing accounts for potential non-germination and allows for the necessary thinning process later.
The seeds must be thoroughly watered immediately after planting to ensure good seed-to-soil contact and initiate germination. The soil surface should remain consistently moist, but not saturated, until the seedlings have successfully emerged.
Care and Maintenance Through Growth
Once seedlings have developed their first true leaves and reached three to four inches in height, thinning must occur to ensure adequate space for mature growth. Thin plants that were direct-sown or started indoors too closely so that the remaining plants are spaced twelve to eighteen inches apart. This spacing prevents competition for light and nutrients, leading to larger, healthier plants with better air circulation.
Kale requires consistently moist soil throughout the growing season, particularly during warmer spells, to maintain tender leaves. Deep, infrequent watering is preferable to shallow daily sprinkling, as this encourages a strong, deep root system. Dry soil stresses the plants and causes them to develop a harsher, more bitter flavor.
Kale is a moderate feeder, benefiting from light fertilization every four to six weeks, especially with a nitrogen-rich formula to support lush foliage growth. Organic options like compost tea or a balanced liquid fertilizer can be applied directly around the base of the plant, avoiding contact with the leaves. Over-fertilizing can lead to excessive, floppy growth, so moderation is advised.
Remain vigilant for common brassica pests, including small green cabbage worms and clusters of aphids on the undersides of the leaves. Simple organic control methods include physically removing pests by hand or applying an insecticidal soap or a Bacillus thuringiensis (Bt) product. A light autumn frost will not damage the plants; exposure to cold temperatures triggers the conversion of starches to sugars, which significantly improves the sweetness of the leaves.
Harvesting the Leaves
Kale is typically ready for its initial harvest approximately 50 to 60 days after planting. The leaves are ready to be picked when they reach the size of a human hand, though smaller leaves are generally more tender and sweeter. Harvesting should be done using the cut-and-come-again method to promote continuous production throughout the season.
Select the older, lower, and outermost leaves of the plant first. These leaves should be snapped or cut off cleanly near the main stem, ensuring that the central growing point or terminal bud remains undisturbed. Leaving the top four to five small, inner leaves intact allows the plant to continue photosynthesizing and producing new foliage for subsequent harvests.