Kale (Brassica oleracea var. sabellica)
Kale is a hardy, cool-season green from the cabbage family that thrives in spring and fall, withstanding even light frosts. It is a versatile vegetable, often used in salads or as a garnish. Kale stands out for its impressive nutritional profile, being rich in minerals and vitamins A and C, and is considered one of the most nutrient-dense vegetables by fresh weight. Although cabbage is less notable for its protein, vitamin, and mineral content, both it and other leafy greens are widely cultivated. These greens are grown for fresh consumption and processed into various products.
Temperature
These crops thrive in monthly average temperatures of 60–65°F but struggle with temperatures consistently above 70°F. They are prone to bolting, which is the premature development of a flower or seed stem. Bolting typically occurs after prolonged exposure to low temperatures (below 50°F), followed by a period of warmer conditions. Such temperature extremes accelerate the rapid growth of the seed stem. Bolting-related losses are common, especially in overwintered crops subjected to severe temperature fluctuations.
Soil
Kale thrives in deep, fertile, well-drained loamy soil rich in organic matter, with a pH of 6.0–7.5. Maintaining consistent moisture levels ensures the highest quality leaves.
Planting
Kale can be planted anytime from early spring to early summer. For a fall harvest, plant it in late summer and continue harvesting until the ground freezes in winter. Thin the seedlings approximately two weeks after planting.
Direct Seed: Plant from early spring until about three months before the anticipated fall frost. For bunching, sow 3–4 seeds every 12–18 inches, ½ inch deep, with rows spaced 18–36 inches apart, and thin to one plant per group. For baby leaf production, sow 60 seeds per foot in a 2–4 inch wide band, planting ¼–½ inch deep.
Early Spring Crop: Choose varieties suited for warm-season production. Sow 2 seeds per cell in 50- to 72-cell plug flats, 3–4 seeds per inch in 20-row flats, or in outdoor beds at a depth of ¼ inch. Seedlings will be ready for transplanting in 4–6 weeks. Maintain soil temperatures above 75°F until germination, then reduce air temperature to around 60°F. Transplant seedlings outdoors, spacing them 12–18 inches apart in rows 18–36 inches apart.
Fall Crop: Start seedlings in May using the method described above, and transplant them to the garden in June or July.
Winter Crop: Kale can be successfully grown in regions with mild winters, where temperatures rarely drop below 32°F. In these areas, transplants can be planted from September through February.
Spacing
12-24” in the row
18-36” between rows
Harvest
Begin harvesting kale about two months after planting by clipping individual leaves. Kale is extremely hardy, and its flavor improves in late fall with light frosts. Harvest tender kale leaves when they feel soft and avoid those with tough stems. Leaves are ready for picking when they are about the size of your hand. Harvest about a fistful of leaves at a time, ensuring you do not pick the terminal bud at the plant's center, as it keeps the plant productive. Kale will continue growing until temperatures drop to 20°F and develops a sweeter flavor after light frosts.
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