How to grow Kale Organically

From seed to harvest

In recent years the humble kale (Brassica oleracea) has become something of a garden hero with it’s elevation to a ‘superfood’ in 2008. It is said to have more absorbable calcium than a small carton of semi skimmed milk. It’s rich in vitamins A, C, E, and K and contains folate, magnesium and potassium. So no surprises that it’s status as a health food from kale chips to smoothies is cemented in our current thinking.

From the classic curly green types to the elegant Cavolo Nero (Tuscan kale) and the striking Red Russian, there’s a kale for every plate and every plot. Growing this healthy vegetable organically is easier than you might think. Whether starting it in seed/module trays for transplanting when true leave appear or sowing directly in the ground. Below we will go over each step with some tips and hints along the way.

Growing Kale in Module Trays

Planting: Kale seeds are small, dark, and round, rather like tiny peppercorns. To sow in trays, choose a peat-free seed compost and fill your modules or tray to the top. Water the compost prior to sowing. Place one seed per cell at about 1/2 to 1 cm deep, or about 3 cm apart if using a seed tray. Cover the seed with the compost and firm in gently to ensure the seed has good contact with the soil. Keep the compost consistently moist, not soggy, as I always say they are seeds, not ducks, no plant like soggy feet.

Germination: Kale germinates best between 15–20°C, so in the UK or USDA zone 9, sowing from April to June will give summer crops a good start, while July to September sowings are perfect for overwintering varieties that will sweeten in the frost. This means that you can pretty much have an almost year round supply of this healthy veg.

Planting out: The seedlings first produce rounded seed leaves (cotyledons), followed by their true leaves—miniature versions of the kale variety you’re growing, complete with curly, flat, or spear-shaped edges. When they have 3–4 true leaves, they’re ready to move outdoors. Harden them off for a week first by gradually introducing them to outdoor conditions. Transplant into rich, fertile soil that’s been improved with plenty of compost or well-rotted manure, spacing each row about 45 cm apart and each plant about 50 cm apart. You can get away with reducing the spacing for something like ‘Cavolo Nero’ which doesn’t fill out quite as much. Although spacing is important, I wouldn’t fret too much if you are a few centimetres out. When transplanting into it’s final position firm the soil around the base of the plant. The brassica family like to feel secure in the ground. I always go round the base of the plant with my fists to compress the soil a little to ensure stability. Once in the ground give it a good drink.

Care and Pests: Kale loves an open, sunny position with free-draining soil. It’s also tolerant of cooler weather, which makes it a reliable crop in temperate climates. Once established, plants need little care beyond watering in dry spells and keeping an eye out for pests. In summer, flea beetles can riddle the leaves with holes and slugs can be an issue at ground level, so organic barriers such as crushed eggshells, wool pellets, or beer traps can be effective. Cabbage white caterpillars and pigeons, are partial to kale and can cause significant damage to your plant. So be vigilant, hand picking caterpillars from the plant or using a garlic wash/spray can help keep infestations down. Netting your crop will also help but make sure there are no holes or gaps. Butterflies are beautiful, but you don’t want them laying eggs on you kale leading to a caterpillar party on your kale leaves. Even with netting, I would still check for pest every couple of days. Mulching with compost or straw helps conserve moisture and keeps weeds down, giving your kale the best chance to thrive.

You’ll usually be ready to harvest leaves 8–10 weeks after sowing. Pick the lower or outer leaves first and keep the central crown intact for ongoing production right through the season.

Sowing tips summery for starting in seed trays

• Seeds are small, dark, and round—sow one per cell, about 1 cm deep.
  • Use peat-free seed compost and keep the soil moist (not waterlogged).
  • Germination is best at 15–20°C (7–10 days to sprout).
• When to sow
  • April–June → for summer/autumn crops
  • July–October → for overwintering crops (sweeter after frost)
• Transplanting
  • Harden off seedlings with 3–4 true leaves before planting out.
  • Space rows about 45 cm apart in fertile, well-drained soil enriched with compost or manure.
  • space each plant about 50 cm apart
  • Kale thrives in sun but tolerates partial shade.
• Pest protection
  • Use fine mesh or netting to protect from pigeons and cabbage white butterflies.
  • Hand-pick caterpillars or try organic garlic spray if infestations build.
• Harvest
  • Ready 8–10 weeks after sowing.
  • Pick lower or outer leaves first, leaving the central crown to keep producing.

Growing Kale Directly in the Ground

Planting: If you prefer to keep things simple, sowing direct into the soil can be just as effective. Prepare your chosen kale patch by removing weeds and adding in plenty of organic matter or peat free compost from a reputable garden centre. You can then either sow seeds thinly in shallow drills about 1 cm deep, leaving around 45 cm between rows and thin out later leaving only the strongest plants (like you might thin carrots). Alternatively sow individual seeds about 50 to 60 cm (24 inches) apart. This is obviously a slightly longer process and a wee bit more fiddly, but cuts out the need to thin out the weaker plants later. Either way leave about 45 cm (17 inches) between each row. I much prefer trying to sow seeds individually as I always feel a little guilty about the seedlings that are discarded when thinning out 😂

Cover the rows with compost and firm in gently. Water each row being careful not to disturb the newly planted seeds (a watering can with a rose attachment will work best). Don’t blast them with a hose as you risk disturbing the soil and dislodging the seed.

Seedlings usually appear (usually within 7–10 days). Proper spacing improves airflow, which lowers the risk of pests and disease. Keep the area as weed free as possible and keep moist – again they are seeds not ducks! so avoid waterlogged soil.

Protection: By the time true leaves appear, you’ll already notice their characteristic kale shape. Protect seedlings with netting that is well secured without gaps if you can. To avoid repeating myself, refer to the paragraph on Care and pests in the planting in seed trays section above. It contains tips on controlling pests like slugs and caterpillars.

Maturing and Harvesting: Your kale plants should take around 40 to 75 days to fully mature. However, if you grow them for use as baby greens, you may be able to harvest them in as little as 4 to 6 weeks. Harvesting is best done gradually. Pick the outer leaves as you need them. This allows the plant to keep producing from the centre. This “cut-and-come-again” approach means one kale plant can feed you for months. In fact, kale is biennial, meaning it grows leaves in its first year and flowers in its second. If you keep harvesting regularly and don’t let the plant get too stressed, it will remain productive until spring. Left unharvested, it will eventually bolt—sending up flower stalks and going to seed.

Sowing tips summary for direct planting

• Sowing tips
  • Prepare the ground with compost or manure.
  • Sow seeds thinly in shallow drills (1 cm deep), rows 45 cm apart.
  • Thin seedlings gradually, let the strongest plants grow on
• When to sow
  • for summer/autumn crops
  • July–September → for overwintering crops (sweeter after frost)
• Protection & care
  • Cover seedlings with netting against flea beetles and pigeons.
  • Use organic slug controls: crushed eggshells, wool pellets, or beer traps.
  • Mulch with compost or straw to retain moisture and suppress weeds.
• Harvest
  • Pick outer leaves regularly (“cut-and-come-again”).
  • Plants stay productive from summer into winter and early spring.
  • Kale is biennial → best harvest in year one, goes to seed in year two.

Whether sowing directly into the soil or starting in seed trays, take steps to ensure a steady supply. Try succession sowing every 3–4 weeks during the main season.

Kale also benefits from companion planting: growing it alongside onions, garlic, or herbs like dill can help deter pests naturally. Because kale is a heavy feeder, rotate it with legumes (such as beans or peas) in following seasons. This will help add nitrogen to the soil so improving soil health.

Don’t forget that if your space is limited you can try growing in pots. You can pop a few seeds in a pot as you would for direct sowing and thin out as they start to grow. Or transplant one of your seed tray seedlings when it has it true leaves. Make sure your pot has good drainage, is at least 30 cm (10 to 12 inches) deep, and mulch around the top to lock in moisture. I would also consider covering with a piece of netting to protect from those pesky caterpillars.

Finally, don’t be afraid to experiment with different varieties of kale. Cavolo Nero’s long, dark leaves are stunning in both the garden and on the plate. Red Russian offers a softer, sweeter leaf with striking purple veins. The classic curly kale remains a tough, winter-hardy staple. With good soil, a little protection, and steady harvesting, your kale patch can keep you in fresh greens for much of the year.

For more tips on growing hardy superfoods see this post Grow your own spinach or for beginner organic gardeners see How to start your first organic veg garden

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