Plan the perfect garden with our interactive tool →

How to Start Sunflower Seeds Indoors


Sunflowers bring bright color to the garden. With flowers ranging from just a few inches in diameter to larger than a foot across, these flowers come in tall varieties and small dwarf plants suitable for growing in a pot on a balcony. Petal colors range from pale yellow to deep oranges and red. Some varieties are grown for their edible seeds while others are grown as an ornamental. While sunflowers can be started successfully when direct-seeded in the garden, starting sunflowers indoors gives you a jump-start on the growing season.

Fill individual peat pots with a potting soil mix. Make your own mix by combining 1-part peat moss and 1-part compost with 1-part vermiculite.

Sow two seeds per peat pot. Sow in the center of the pot and cover with 1/2 inch of potting soil for dwarf varieties and 1 inch for giant varieties.

Water the soil until it is evenly moist throughout. Cover in plastic wrap and place in a warm, sunny window to germinate. Germination takes approximately 14 days.

Remove the plastic once seeds germinate. Continue watering to keep the soil moist but not soggy. If both seeds germinate, remove the weaker seedling once the stronger seedling has produced its second set of leaves.

Transplant outdoors once all danger of frost has passed in your area. Harden off the seedlings by setting them outdoors for 2 to 4 hours a day for 7 days before transplanting.

Cut off the bottom of the peat pot with a sharp knife. Plant each sunflower, pot included, so the top of the pot rim is just under the soil surface. Space giant sunflowers 3 feet apart and dwarf varieties 1 foot apart.


Instead of transplanting outdoors, transplant dwarf varieties into permanent 8-inch pots once they develop their third set of leaves.

Sunflowers require well-drained soil in full sun.

Apply a phosphorous fertilizer to the sunflowers when they begin to form buds to encourage larger blooms.

Harvest sunflower seeds after the petals whither away and when the flower back starts to yellow.


Cover seed heads with a mesh bag if birds or squirrels are stealing the seeds.

Sunflowers are not frost-hardy and a mild frost will kill or damage the plants.

Garden Guides