Planting Sunflowers: Planting Sunflower Seeds & Starting from Root Divisions

Planting sunflowers that will thrive year after year requires the right combination of fertile soil, sunlight and water. Choose a well-drained spot where they’re guaranteed full sun for at least 8 hours a day in the summer.

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You also want to be sure that the ground has warmed up to at least 70 degrees F (21 C) before you plant.

To satisfy this tall flower’s appetite for nutrients, the soil should be fertilized with well-rotted organic farmyard manure before planting. For perennial sunflowers, a mulch of compost should be added ahead of time in the fall.

When planting, make a hole in the soil between 1 and 3 inches (2.5 and 7.5cm) deep, then drop in two seeds. If you're going for multiple sunflowers, plant about 20 inches (50 cm) apart.

Once your seeds have germinated (should occur within about a week) you can remove the weaker seedling. Water well and make sure seedlings do not dry out as they begin to grow. Mark the ground with a plant label so you remember where to water until the seedling sprouts.

If your growing season is limited due to a chilly spring, consider planting sunflower seeds indoors in pots filled with an organic seed-starting mix. Transplant them as soon as the risk of frost has passed. If you’re growing a tall sunflower variety, it’s very important not to restrict growth by a too-small pot, as they’ll never catch up from the missed growth.

For container growing, choose dwarf varieties. Unusual varieties like Teddy Bear will make wonderful plants that can be treated as bedding to fill patio containers or gaps in your flower beds.

Transplanting Sunflowers

Sunflowers don’t like being transplanted, so it’s usually better to sow them directly into the soil.

This is especially true of the tall varieties like Mammoth Russian or California Greystripe.

To start from root division - for perennial sunflowers like Lemon Queen and debilis (beach sunflower), dig up the plant to be divided in the fall. Separate the plant into two or three sections.

Usually it’s best to cut out the middle section of the plant as this is often the weakest. Replant and water immediately.

Snapshot: Planting Sunflowers

  • Germination soil temperature: 70 degrees F (21 C)
  • Distance between plants: about 20 inches (50 cm)
  • Planting depth: 1 to 3.5 inches (2.5 to 9cm)
  • Days to germination: 5 to 7 days
  • Preferred soil pH (see soil pH tester for more information): 6 to 7.2
  • Root division information (perennials only):
    • Root system type (clumping, spreading, rhizome or tuber): rhizome
    • Roots division frequency: Every 3 to 4 years
    • In which season should dividing occur? Fall

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