Tournesol géant

Helianthus annuus

Plant Description

Giant Sunflowers are bold, towering annuals with broad green leaves and huge golden-yellow flower heads that can reach over a foot in diameter. Known for their sunny charm and dramatic height—often growing 8–12 feet tall—they’re a showstopper in any garden and a magnet for pollinators.

These fast-growing plants are easy to grow from seed and bring joy to kids, gardeners, and wildlife alike. The large central disk is packed with seeds that mature into a snack for birds—or for you!

Quick Facts

  • Sunlight: Full sun (6–8+ hours daily).
  • Days to Sprout: 7–14 days.
  • Days to Harvest: 70–100 days for mature flower heads and seeds.
  • Plant Spacing: 18–24 inches apart to support large root systems.
  • Seeds per Hole: 3 seeds per hole; thin to the strongest seedling.
  • Plant Type: Annual (completes lifecycle in one season).
  • Planting Depth: 1 inch deep.

Best Planting Locations

  • Sunny Borders: Perfect for the back of flower beds or along fences where their height can be showcased.
  • Against Walls: A great way to create vertical interest and reflect heat and light to boost growth.
  • Children’s Gardens: Easy to grow and fun to watch—they’re a favorite for kid-friendly garden projects.
  • Pollinator Patches: Their massive blooms attract bees, butterflies, and birds throughout the season.

Getting Started

  1. Direct Sow: Plant seeds directly outdoors after the last frost when soil reaches ~60°F. Sunflowers dislike transplanting.
  2. Soil Needs: Loose, well-draining soil enriched with compost. Avoid overly rich soil—too much nitrogen encourages leafy growth over blooms.
  3. Support Growth: Water well after planting and protect young seedlings from birds and slugs with netting or covers.

Companion / Enemy Plants

Good Companions: Corn, squash, cucumbers (as natural trellises), beans, and lettuces.

Avoid Planting Near: Potatoes and pole beans, which may compete or interfere with sunflower root exudates.

Attractants / Repellents

Attracts: Bees, butterflies, and seed-eating birds.

Repels: Can help deter some soil nematodes through root exudates, and tall growth may provide shade for heat-sensitive crops.

When to Plant

  • Cool Climates: Sow seeds 1–2 weeks after last frost when soil is warm and workable.
  • Warm Climates: Plant in early spring for summer bloom; a second round in midsummer provides early fall flowers.

Maintenance

  • Watering: Water deeply once a week; more often during dry spells. Avoid overhead watering once blooms emerge.
  • Fertilizing: Light feeding with compost or low-nitrogen fertilizer mid-season promotes flower size without excess foliage.
  • Staking: For varieties over 6 feet tall or exposed to wind, provide support stakes or grow near a fence.

Harvest

  • For Flowers: Cut stems when petals begin to unfurl. Use immediately or hang upside down to dry.
  • For Seeds: Wait until flower backs turn yellow and seeds are plump and firm. Cover with mesh to protect from birds if needed.
  • Drying Seeds: Cut heads, remove loose petals, and let dry indoors for 1–2 weeks before removing seeds by hand.

Uses

  • Edible Seeds: Toasted sunflower seeds are nutritious snacks and salad toppers. Unroasted seeds can be saved for planting next season.
  • Cut Flowers: Stunning additions to bouquets or centerpieces—long stems and vivid color add drama.
  • Wildlife Habitat: Seeds feed birds, and flowers support bees, making sunflowers a biodiversity booster.
  • Natural Trellis: Use sturdy sunflower stalks as vertical supports for vining crops like pole beans.

How to Store

  • Seeds (Unroasted): Store in a cool, dry place in an airtight container. Label with harvest date and variety for next year’s planting.
  • Bouquets: Keep in water and recut stems every couple of days. Lasts 5–7 days indoors.
  • Dried Flowers: Hang upside down in a warm, ventilated space for 7–10 days. Use in arrangements or crafts.