Growing Tips: Sunflower

Quick Reference:

Annual, a plant that completes it’s life cycle in one season. Cover seed with 1/4 inch of soil spaced 8 to 10 inches apart. Germination: 10 to 14 days. Ideal plant spacing in the garden is 16 to 24 inches. Plant height: 48 to 60 inches. Shallow planting provides warmer soil but soil MUST be kept moist at all times until plants emerge.

When and where to plant:

Sunflowers prefer to be planted where they will grow all summer, they do not transplant well. Select a warm, sunny, garden area that has good, well-drained, garden loam, cultivate the soil, enrich with plant food and plant after the last frost. In Alaska, because it takes a long season to mature these large plants it is recommended that they be started indoors in individual, 4 to 6 inch, plastic pots, 4 to 6 weeks before the last frost. Fill plastic pots that have drainage holes, with a good garden loam, plant 2 or 3 seeds, firm soil over seed, water well and keep moist. When seedlings show their first green leaves, water with a liquid solution of plant food and place pots in full sun where they have cool nights. Keep soil moderately moist, water with a liquid solution of plant food every 2 weeks and grow indoors until the garden has warmed. After the last frost, dig a hole for the seedling, fill it with water, moisten the soil in the plastic pot then carefully slide the moist root ball out of the plastic pot to avoid injuring the roots, place the root ball in the hole and press the moist soil around the root ball. Water the plant well to help reduce transplant shock.


Growth is maximized in good soil with moderate moisture and two applications of plant food one month apart during the summer. In a windy location these tall plants will require staking.


When the seed heads are mature, indicators are the back of seed head has turned brown and dry, most of the yellow petals have fallen off and the seeds are plump, cut seed heads leaving about one foot of stem attached . Rub the seeds out of the head by hand, dry seed then store seed in a cool dry place.