Brassica oleracea

Sowing and growing tips for Brassica oleracea

Brassica oleracea seeds germinate reliably in fertile, moisture-retentive, well-drained soil with a neutral to slightly alkaline reaction. Choose full sun, though light shade is tolerated. For early crops, start under cover before the last frost; direct sow when soil is workable and frost risk has passed. Late summer sowing suits autumn harvests, and in mild climates autumn sowing can establish overwintering types. Transplant into firm soil, spacing to allow good air flow (follow packet guidance as sizes vary from compact to medium-tall). Keep evenly moist, mulch to steady moisture, and feed modestly if growth slows. Rotate beds, remove yellowing leaves, and protect young plants from common pests with mesh or fleece where needed.

• Sow under cover before the last frost; direct sow when soil is workable; late summer for autumn harvest; autumn sowing in mild climates for overwintering types.
• Provide fertile, well-drained yet moisture-retentive soil, neutral to slightly alkaline; keep evenly moist and mulch to conserve moisture.
• Space for good airflow, firm plants in well, stake taller types in windy sites, and rotate beds to limit pest and disease build-up.
• Many cultivated forms are grown for edible heads, leaves or stems.
• Some varieties have striking foliage and form, valued for ornamental effect.
• Compact selections can be grown in deep containers; steady watering and light feeding support consistent growth.

How do you grow Brassica oleracea from seed?

Sow seeds 0.5–1 cm deep in trays, modules, or a fine seedbed, keeping them evenly moist in cool to mild conditions; steady temperatures and gentle airflow support sturdy seedlings. For early crops, start under cover before the last frost so plants are ready to set out once the soil is workable and frost risk has passed. Prick out or pot on before roots become crowded, and harden off gradually. Transplant with the first true leaves well developed, planting firmly at the same depth (kale can be set slightly deeper). Compact types can be grown in generous containers with good drainage and moisture-retentive compost.

When should brassicas be sown after the last frost and through the season?

After the last frost, direct sow once soil is workable and not waterlogged, or transplant starts raised under cover. For summer and early autumn harvests, sow from late winter under cover and continue outdoors in spring (Northern Hemisphere) / autumn (Southern Hemisphere). For autumn harvests, a late-summer sowing works well as days begin to cool. In mild climates, autumn sowing of hardy types allows overwintering for late winter to spring harvests; protect young plants from severe cold and excess wet.

What soil and sun conditions suit Brassica oleracea best?

Provide full sun for best growth, with tolerance of light shade in hotter or highly exposed sites. A fertile, well-drained yet moisture-retentive soil is ideal; incorporate well-rotted organic matter to boost structure and water holding. Neutral to slightly alkaline conditions favour strong roots; on notably acidic soils, many gardeners adjust pH toward neutral before planting. Maintain even moisture, mulch to steady soil temperatures, and avoid waterlogging. In containers, use a quality, firmed mix that drains freely but does not dry out quickly.

Is it better to direct sow or transplant brassicas?

Both methods work: direct sowing avoids transplant shock and can produce deep-rooted plants, while raising transplants indoors or in a cold frame offers earlier starts, more uniform spacing, and easier protection from pests. Where soils are cold or pest pressure is high, transplants in modules or pots are often more reliable. Whichever route you choose, firm planting, steady moisture, and a brief hardening-off period help plants establish quickly.

How far apart should brassica seedlings be spaced, and how tall do they grow?

Spacing varies by type and variety; follow packet guidance and allow good airflow to limit disease. As a guide, compact kales and kohlrabi can be grown closer, while heading cabbages, broccoli, and cauliflower need more room. Typical final spacings range from about 30–60 cm between plants, with similar or slightly wider row spacing. Heights are generally compact to medium-tall, from roughly 25–90 cm depending on the cultivar and conditions.

What cool-weather, heat, watering, feeding, and harvest tips help with brassicas?

Brassicas prefer cool, steady growth; succession sowing at intervals smooths harvests and avoids gluts. In warm spells, mulch, ample soil moisture, and temporary shade help reduce heat stress and bolting; light afternoon shade is useful where summers are intense. Water deeply and consistently rather than little and often, and feed with balanced nutrition on fertile ground, topping up with compost or a gentle side-dress as plants bulk up. Harvest cabbage when heads feel firm and solid, and cut broccoli while heads are tight, before florets loosen; many broccoli types produce side shoots after the main head is removed.

This guidance summarises standard cultivation practices derived from widely used horticultural references and supplier materials. Conditions vary by microclimate, soil type, drainage, and exposure, so results may differ. Timing should be adjusted to local frost dates and when soil is workable. For the most accurate requirements—including sowing depth, spacing, germination temperatures, and timing—refer to the product page, which provides the specific instructions applicable to that item. Packet directions take precedence.

Cultivation notes for cool-season brassicas

Brassica oleracea seeds perform best in cool conditions with germination typically at 18–24°C. Sow 0.5–1 cm deep in fine, moist seed compost, starting indoors 4–6 weeks before the last frost, or direct when soil is workable and near 10–21°C. Harden off for 7–10 days and transplant at 3–4 true leaves. Provide fertile, well-drained soil with a pH around 6.0–7.5, full sun, and steady moisture; mulch helps retain even soil temperature and moisture. Space plants 30–60 cm apart, with 45–75 cm between rows, adjusting to the cultivar’s mature size. Netting or row covers can deter insect pressure, and rotating beds on a 3–4 year cycle supports soil health. In mild climates, autumn sowing may be possible for cool-season cropping. Consistent watering, timely thinning, and vigilant weeding encourage uniform heads and stems. Seed listings and general guidance are maintained by SeedsChoice, supporting careful selection of types suited to timing, space, and local growing conditions.