Sunflowers are iconic, easy-to-grow plants enjoyed by gardeners in every state. One of the easiest flowers to grow, Helianthus thrive in full sun and aren’t picky about soil. You’re probably most familiar with the giant types that grow very tall and have oversized yellow flowers. But there are many other types of sunflowers to explore.
BASICS
Botanical name:
Helianthus spp.
Hardiness Zones:
Usually grown as annuals; perennial varieties 4-8 depending on cultivar
Height:
Varies; giant varieties up to 16 feet tall, dwarf varieties 1 to 4 feet tall
Exposure:
Full sun, 6+ hours per day
When do sunflowers bloom?
Annual sunflowers bloom during summer and into autumn. Sow new plants every few weeks and you’ll enjoy non-stop flowers until the first frost. Perennial sunflowers bloom for a period of 8-12 weeks with some beginning as early as July and others finishing as late as October.
When to plant:
For annual sunflowers (Helianthus annuus), sow seeds outdoors after the threat of frost has passed. If you have a short growing season they can be started indoors. Perennial sunflowers should be planted in spring or fall
Soil:
Any; clay, sandy, silt or loam.
Spacing:
For giant sunflowers, or those grown for seed production, sow seeds 2 to 3 feet apart. For smaller annual types popular for cut flower gardens, you can sow seeds about 6 inches apart.
SUNFLOWER CARE
Watering:
Once established, they will tolerate some drought. However, in the periods before, during and after flowering, they perform best with deep, regular watering.
Fertilizing:
In most cases, they will not need fertilizer. However, if your soil is very poor you can use a slow-release granular fertilizer to encourage larger flowers. Be careful – too much nitrogen can inhibit flowering.
Staking:
Sunflowers that grow over 3 feet tall or have large, heavy flower heads are vulnerable to flopping or even breaking under the stress of summer winds and rain. Loosely attach your plant’s branches to stakes with cloth or twine to prevent this problem. Sunflowers grown from seed sown directly in the garden will have well-established roots and stronger stems and be less likely to fall.
To further encourage proper root growth, provide well-draining, organically-rich soil, and plenty of space between plants. And don’t forget to water deeply so that the roots will grow down rather than out.