How to Grow Kale Seeds

Grow Guide #2278
Family: Brassicaceae
Binomial name: Brassica spp.
Life Cycle: Biennial (usually grown as an annual)

This 'How to Grow' guide details everything a home gardener needs to know to plant, grow and care for Kale (Brassica spp.).

When to Sow Kale Seeds

Kale is a cool season crop. Use the table below to identify the best time of year to sow kale in your climate.

  JAN FEB MAR APR MAY JUN JUL AUG SEP OCT NOV DEC
Cool
Temperate
Sub-Tropical
Tropical
Arid

Preparation

Kale plants are best grown in full sun. Choose a location that will receive at least 6 hours of full sun each day.

Kale plants need a well drained soil enriched with plenty of organic matter. Prepare soil by weeding it thoroughly, digging it over to loosen it and adding aged animal manure or compost. Keep the area free of weeds until planting. Learn more about preparing soil for planting here.

How to Sow Kale Seeds

Kale seeds do not require any treatment (eg soaking, stratification) before sowing.

Kale seeds can be sown directly into the garden OR seedlings can be raised in trays or other containers and transplanted to the garden once established.

Sow Direct

  1. Sow seeds directly in the garden 10mm deep and 40-60cm apart, with rows 50-100cm apart.
  2. Keep soil moist but never wet or dry.
  3. Seeds should germinate in around 6-12 days at a soil temperature of 8-30°C.
  4. Young seedlings will need protection from pests, pets and weather until they are established.

Raise Seedlings

  1. Fill trays, punnets or jiffy pots with a good quality seed-raising mix, or use soil starter pellets.
  2. Sow seeds 10mm deep.
  3. Keep soil moist but never wet or dry.
  4. Seeds should germinate in around 6-12 days at a soil temperature of 8-30°C.
  5. Transplant seedlings to the garden once they have their first true leaves and are large enough to handle (usually 5-10cm tall).
  6. Plant out, spacing plants 40-60cm apart, with rows 50-100cm apart.

Kale is a cool season crop that will bolt in very hot weather. Do not transplant seedlings or sow seeds outside in very warm temperatures.

How to Grow Kale

Kale plants may need watering during the growing season. Water when the soil is dry about 5cm below the surface (test this by scratching away a little soil with your finger). Water deeply in the early morning or late afternoon. Avoid watering the leaves of plants to avoid fungal diseases. Learn more about watering here.

If soil was well prepared no extra fertiliser should be necessary. In poor soil or to give your plants an extra boost, application of a high-nitrogen fertiliser or one formulated for leafy greens or herbs can be beneficial:

  • Apply slow release fertiliser at the recommended rate when transplanting or when seedlings are 5-10cm tall.
  • Apply liquid fertiliser at the recommended rate and frequency during the growing season.

How to Harvest Kale

Kale should be ready to harvest in approximately 50-70 days.

Kale plants are ready to harvest when the leaves are large enough to eat. Harvest individual leaves by cutting or twisting the outer leaves close to the stem, leaving some for future growth. Store kale leaves in a perforated plastic bag in the fridge. For longer term storage kale can be blanched then frozen.

Common Problems when Growing Kale

Like all plants, kale is susceptible to some pests, diseases and other problems. Below is a list of the most common problems gardeners encounter when growing kale plants:

  • Aphids
    Aphids are small (2-4mm long) sap-sucking insects that congregate on the new shoots or the undersides of leaves. They can cause leaves to wilt or become discoloured, and also excrete honeydew which can attract ants and other insect pests. To manage aphids, remove them by spraying with a garden hose, apply a soap or alcohol spray, or encourage predatory insects to your garden. Read more about aphids here.
  • Bitter Leaves
    Bitter taste can be caused by plants growing too slowly, suffering a setback in growth or being harvested too late. Enrich soil with aged manure before planting, ensure plants are watered deeply and regularly, and harvest when they are young and tender.
  • Bolting is when a plant prematurely flowers and goes to seed. Bolting can be caused by a period of extreme weather. Avoid sowing seed until after the danger of frosts has passed or in very hot weather. Water plants regularly and deeply in hot weather to prevent them suffering heat stress.
  • Cabbage moth
    Cabbage moth and cabbage white butterfly have white or grey wings with distinctive markings. They lay their eggs on the underside of leaves. Their caterpillars feed on the leaves, creating large holes and sometimes skeletonising the leaves. Use netting to exclude butterflies and moths or decoys to deter them. Pick the caterpillars off the plants or use an appropriate spray in a selective and targeted way. Read more about cabbage moth and cabbage white butterfly here.
  • cutworm
    Cutworms are moth larvae that live in the soil, emerging at night to feed. The caterpillars are 3-4cm long and white, grey or brown in colour. They can chew through the stems of tender seedlings, felling them at ground level. Remove cutworms by hand at night or use cardboard collars to protect the stems of seedlings.
  • Animal eating fruit
    Possums, birds and other animals can ruin a large percentage of your harvest overnight. Physically exclude pests by using netting or cages, or try spraying plants with a pungent homemade spray made from garlic, fish oil or mustard.
  • Powdery Mildew
    Powdery mildew is caused by fungal spores reproducing on the leaves of plants. First showing as white spots on leaves, affected areas can spread quickly to cover the entire leaf surface. While rarely fatal, powdery mildew can reduce yields. Water plants at soil level (not on leaves) to prevent spreading spores, allow good air flow between plants, remove affected leaves and if necessary spray with an appropriate fungicide or homemade spray. Read more here about powdery mildew here.
  • Whitefly
    Whitefly is a sap-sucking insect related to aphids. They are often found in large numbers on the underside of leaves and will swarm in clouds when disturbed. Plants may have yellowing leaves or may wilt, and growth will be slowed. Whitefly can be removed with a garden hose or sprayed with soap spray. Badly affected plants should be destroyed. Attracting beneficial insects that will prey on whitefly can be beneficial. Read more about managing whitefly here.

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