Growing Guide: Sunflowers


  • Wait until the soil temperature reaches 55-60F.
  • Choose a location with direct sunlight for 6 to 8 hours per day.
  • Sunflowers thrive in slightly acidic to somewhat alkaline (pH 6.0 to 7.5) conditions. Soil should be nutrient-rich with organic matter or composted.
  • When choosing where to plant sunflowers consider that once blossoms open, they will face east. Also, because sunflowers are so tall, they should be planted on the north side of the garden to prevent shadowing other plants.
  • Planting sunflowers along a fence or near a building will prevent them from falling over. Also, tying bamboo sticks to the stem can assist with anchoring the plant from gusty winds.

How to Grow Sunflowers 

  • Sunflowers have long tap roots so plant seeds about 1 to 2 inches deep in well drained soil 6 inches apart. Thin plants to about 2 feet apart. Sunflowers will mature and develop seeds in 80 to 120 days.
  • Sow new seeds by staggering planting every 2 to 3 weeks to enjoy continuous blooms until the first frost!

Common Pests of Sunflowers

  • Fungal diseases such as mildews and rusts can infect sunflowers. The oldest leaves are usually infected first. You should remove and destroy seriously infected plants.
  • Small gray sunflower moths sometimes lays their eggs in developing sunflower blossoms. Simply pick the worms from the plants, mash them, or drop them into a plastic bag.
  • Birds and squirrels can be a problem when seeds ripen and harvest time approaches. Simply cut away the few leaves that are closest to the heads to make it harder for birds to perch and feed. You can cover the flowers with a light fabric such as cheesecloth. Spread the netting over the planted area until seeds germinate.
  • Keep the area weeded and clean up plant debris from the garden in the fall.

Harvesting Sunflowers

  • The reverse side of the flower will turn from green to a yellow-brown — this happens about 30 to 45 days after bloom.
  • Cut off the seed heads with a foot or so of stem attached and hang them in a warm, dry place that is well-ventilated away from mice and birds.
  • When the seeds are thoroughly dried brushing them with your fingers or a stiff brush (a fork also works well). Allow the seeds to dry additional days.