Starburst Greenburst Sunflower Seeds – Overview & Growing Guide

Posted on by My Garden Channel

Starburst Greenburst sunflowers are a unique and eye-catching variety, known for their bold, lime-green central blooms surrounded by frilled, golden-yellow petals. They’re part of the pollen-free Starburst series, making them especially desirable for cut flower arrangements due to their clean appearance and long vase life.

Quick Facts

  • Type: Annual
  • Height: 5–7 feet tall
  • Bloom Size: 4–6 inches
  • Days to Maturity: 60–75 days
  • Sun Requirements: Full sun (6+ hours daily)
  • Soil Preference: Well-draining, moderately rich soil
  • Pollinator Friendly: Yes (though pollen-free, still attractive to bees)

Seed Starting Instructions

When to Sow

  • Outdoors: Sow directly after the last spring frost once soil has warmed to 60°F (16°C) or higher.
  • Indoors: Start 2–3 weeks before your last expected frost date in biodegradable pots (sunflowers dislike transplant shock).

How to Sow

  • Depth: 1 inch deep
  • Spacing: 6–12 inches apart depending on the desired fullness
  • Row Spacing: 18–24 inches if growing in rows

Growing Conditions

Light

  • Full sun is essential for strong stems and abundant blooms.
  • Choose a site with all-day sun if possible.

Soil

  • Prefers loose, well-draining soil enriched with compost.
  • Avoid overly rich soil or over-fertilizing, which can lead to more foliage and fewer blooms.

Water

  • Keep soil evenly moist during germination.
  • Once established, water deeply but infrequently to encourage strong root growth.
  • Do not let soil dry out completely during peak summer.

Fertilization

  • Optional if planted in decent soil.
  • A light side-dressing of balanced fertilizer (10-10-10) once the plants are about a foot tall can promote healthy growth.

Maintenance

  • Thin seedlings if crowded to ensure good airflow and prevent fungal issues.
  • Stake tall plants if grown in windy areas to prevent bending or breaking.
  • Deadhead spent flowers if you want prolonged bloom or remove mature heads to collect seeds.

Pests and Problems

  • Aphids and beetles may appear; treat with insecticidal soap or neem oil if infestations are severe.
  • Birds and squirrels may nibble young seedlings or seed heads—netting or garden fabric can help protect early stages.
  • Fungal issues such as powdery mildew are rare in full sun and with good spacing.

Harvesting for Cut Flowers

  • Cut blooms in the early morning before the heat of the day.
  • Choose flowers that are just starting to open for longest vase life.
  • Place immediately in cool water and condition overnight before arranging.

Saving Seeds

  • Since Greenburst is often a hybrid, saved seeds may not come true to type.
  • If you still want to try, wait until the back of the flower head turns brown and dry.
  • Remove seeds by rubbing the head with your hand and allow them to fully dry before storing.

Ideal Uses

  • Ornamental borders
  • Cut flower gardens
  • Pollinator and wildlife gardens
  • Summer flower beds
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