Flowering kale plants in purple, white, and pink shades growing in pots with text overlay 'How to Grow Flowering Kale from Seed – Step-by-Step Guide to Gallon Pots

How to Grow Flowering Kale from Seed: Step-by-Step Guide from Sowing to Gallon Pots

Flowering kale (sometimes called ornamental kale) is one of the most stunning cool-season plants for adding bold texture and long-lasting color to fall and winter gardens. Unlike traditional kale grown for eating, flowering kale varieties are bred for their colorful, frilly foliage in shades of white, pink, purple, and magenta. These plants thrive in cooler weather and can hold their color well into winter, making them a favorite choice for containers, landscapes, and commercial growers.

In this guide, you’ll learn how to grow flowering kale from seed all the way to gallon-size pots, covering every stage: sowing, germination, transplanting, fertilization, and care.

👉 Shop Flowering Kale Seeds here:

Also, don’t miss our helpful reference on When to Start Seeds Indoors by Zone (Complete Guide) to perfectly time your kale sowings.

Step 1: Understanding Flowering Kale Growth

Flowering kale is a cool-season annual. Its ornamental foliage takes on vibrant colors as temperatures cool, especially after exposure to light frosts. For best color, flowering kale should mature in daytime temperatures of 60–70°F (15–21°C) and nighttime temperatures between 40–50°F (4–10°C).

Growth timeline:

  • Seed to transplantable plug: 4–6 weeks

  • Transplant to gallon pot: 6–8 weeks

  • Full finish time: 10–14 weeks total

Because it grows best in cooler months, flowering kale is often started indoors in late summer for transplanting outdoors in early fall.

Step 2: Starting Flowering Kale from Seed

Germination Conditions

  • Sow indoors: 10–12 weeks before the desired outdoor finish date.

  • Soil temperature: 60–70°F (16–21°C).

  • Light requirements: Flowering kale needs light for germination, so lightly press seeds into the surface of the medium—do not bury deeply.

  • Germination time: 4–7 days.

Sowing Tips

  1. Use a high-quality seed starting mix with good drainage.

  2. Sow 1–2 seeds per cell in a 288-cell or 200-cell plug tray.

  3. Lightly cover with vermiculite to maintain humidity while still allowing light penetration.

  4. Keep media evenly moist but not saturated.

👉 For detailed guidance on timing your sowing by region, check out our Seed Starting Zone Guide.

Step 3: Growing On Seedlings

After germination, move trays to a well-lit greenhouse or grow lights to encourage compact, sturdy growth.

  • Temperature: 60–65°F (16–18°C) days; 50–55°F (10–13°C) nights.

  • Fertilizer: Begin feeding with a balanced 100 ppm nitrogen solution once the first true leaves appear. Increase to 150–200 ppm as seedlings grow.

  • Moisture: Maintain medium moisture at level 3–4 (moist but not saturated).

Seedlings are usually ready for transplanting into larger plug trays or directly into small packs after 4–5 weeks, when they have 3–4 true leaves.

Step 4: Transplanting Flowering Kale

Transplant seedlings into cell packs, 4-inch pots, or directly to 1-quart containers depending on your production plan.

  • Media: Use a well-draining peat-based medium with a pH of 5.8–6.2.

  • Spacing: If growing in packs, allow 8–10 inches between plants. For gallon pots, grow one plant per pot.

  • Fertilization: Continue weekly feeding with 150–200 ppm nitrogen. Avoid excessive nitrogen late in production, as it delays color development.

Step 5: Finishing in Gallon Pots

Growing flowering kale to gallon size creates a premium, retail-ready product perfect for fall garden centers or landscapers.

  • Timeframe: 6–8 weeks from transplant to finished gallon pot.

  • Light: Full sun promotes compact growth and vibrant color.

  • Temperature: Maintain cool conditions; high heat will reduce leaf quality.

  • Watering: Water consistently but avoid over-saturation, as kale is prone to root rot in soggy media.

For best ornamental effect, wait for night temperatures to drop below 55°F (13°C). This triggers the dramatic leaf coloration that makes flowering kale so appealing.

Common Problems & Solutions

  • Stretching (leggy growth): Caused by low light or high temperatures. Use cooler night temps to keep plants compact.

  • Yellowing leaves: Often a result of nutrient deficiency or overwatering. Check fertilizer levels and drainage.

  • Pests: Aphids, flea beetles, and cabbage worms are common. Monitor regularly and treat early.

  • Diseases: Watch for damping-off in seedlings and root rots in overwatered pots. Use sterile soil and maintain airflow.

Harvesting & Display

Flowering kale isn’t harvested like edible kale but rather enjoyed as a display plant. Once plants reach full size in gallon pots, they’re ready for:

  • Fall landscapes

  • Patio containers

  • Seasonal borders

  • Commercial retail sales

Color and form can last well into December and January in many climates.

Related Resources

FAQ: Growing Flowering Kale

Q: Can I direct sow flowering kale outdoors?
A: While direct sowing is possible, it’s not recommended for ornamental production. Starting indoors ensures uniform germination, healthier seedlings, and better timing for fall displays.

Q: How long does it take flowering kale to grow from seed to gallon pot?
A: On average, 10–14 weeks total. About 4–6 weeks to plugs and 6–8 weeks to finish in gallon pots.

Q: Does flowering kale need cold to change color?
A: Yes. Cool night temperatures below 55°F (13°C) are essential for foliage to take on vivid purple, pink, or white tones.

Q: Can flowering kale survive frost?
A: Absolutely! Flowering kale is highly frost-tolerant and can often last through multiple freezes, keeping color in the landscape into winter.

Q: Is flowering kale edible?
A: Technically yes, since it’s a type of kale. However, ornamental varieties are bred for appearance, not flavor, and tend to be bitter compared to culinary kale.

Back to blog