Sunflowers

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Sunflowers (Helianthus annuus) is an annual plant with a large daisy-like flower face. Its scientific name comes from the Greek words helios (“sun”) and anthos (“flower”). The flowers come in many colors (yellow, red, orange, maroon, brown) but they are commonly bright yellow with brown centers that ripen into heavy heads filled with seeds.

Here and yonder, high and low,
Goldenrod and sunflowers glow.

–Robert Kelley Weeks (1840–76)

HOW LONG DO SUNFLOWERS TAKE TO BLOOM?

A fairly fast-growing flower, most sunflower varieties mature in only 85 to 95 days. The largest sunflower varieties grow to over 16 feet in height, while smaller varieties have been developed for small spaces and containers and rarely grow larger than a foot tall! The flower heads can can reach over 12 inches in diameter within the large seeded varieties.

Sunflowers are heliotropic, which means that they turn their flowers to follow the movement of the Sun across the sky east to west, and then returns at night to face the east, ready again for the morning sun. Heliotropism happens during the earlier stages before the flower grows heavy with seeds.

Very few plants are as heat-tolerant, resistant to pests, and simply beautiful. Sunflowers make excellent cut flowers and many are attractive to bees and birds.

At the end of the season, it’s easy to harvest sunflower seeds for a tasty snack or for replanting (see instructions below). Learn more about why you should start growing these happy flowers in your garden.

PLANTING

WHEN TO PLANT SUNFLOWERS

  • It’s best to sow sunflower seeds directly into the garden (or outdoor containers) after the danger of spring frost has passed anytime after soils have warmed to 50°F.
  • In most regions, this will fall between April and mid-July. In the south, this will probably occur in mid-March or early April.

CHOOSING & PREPARING A PLANTING SITE

  • Find a sunny spot! Sunflowers grow best in locations with direct sunlight (6 to 8 hours per day); they require long, hot summers to flower well.
  • Choose a location with well-draining soil. It shouldn’t pool water after it rains.
  • Sunflowers aren’t picky but the soil can’t be too compact. They have long tap roots that need to stretch out; in preparing a bed, dig down 2 feet in depth and about 3 feet across.
  • They’re not too fussy when it comes to soil pH either. Sunflowers thrive in slightly acidic to somewhat alkaline soil (pH 6.0 to 7.5).
  • Sunflowers are heavy feeders, so the soil needs to be nutrient-rich with organic matter or composted (aged) manure. Or, work in a slow release granular fertilizer 8 inches deep into your soil.
  • If possible, plant sunflowers in a spot that is sheltered from strong winds, perhaps along a fence or near a building. Larger varieties may become top-heavy and a strong wind can be devastating.

PLANTING SUNFLOWER SEEDS

  • Sunflowers should be planted 1 to 1-½ inches deep and about 6 inches apart after the soil has thoroughly warmed. If you wish, you can plant multiple seeds and thin them to the strongest contenders when the plants are six inches tall.
  • Give plants plenty of room, especially for low-growing varieties that will branch out. Make rows about 30 inches apart. (For very small varieties, plant closer together.)
  • A light application of fertilizer mixed in at planting time will encourage strong root growth to protect them from blowing over in the wind.
  • Experiment with plantings staggered over 5 to 6 weeks to keep enjoying continuous blooms.
  • If you see birds scratching around for the seeds, spread netting over the planted area until seeds germinate.