By Mary-Jane Pilgrim, Master Gardener
The weather outside at this time of year is a bit frightful, so as a diversion, let’s vault ourselves temporarily into mid-summer and learn about that giant of summer flowers — the sunflower. In all their colourful glory, these plants are a happy sight to behold—but there’s more to their nature than just beauty. The multipurpose plants deliver healthy snacks for us, useful oils, and seeds for our feathered friends.
Sunflowers are members of the family Asteraceae, which all form a composite head (capitulum) made of masses of simple flowers (florets) that each produce a seed if successfully pollinated. Sunflowers typically have between 1,000 to 1,400 florets, and potential seeds, per head. The capitulum is surrounded by petals, making the whole structure seem like one single flower. The latin name for the common sunflower is Helianthus.
Butterflies, beneficial insects, hummingbirds and birds flock to sunflower heads for food, pollen and nectar. Insects enjoy the flower pollen and nectar while birds feast on the seeds. Plant tall varieties along a fence to block an unsightly view, or try them in the back of the flower border or along the side of the house or garage. You can also use sunflowers instead of corn in a Native American ‘Three Sister’s Garden’: Plant pole beans to grow up the clump of 3-week old sunflower stalks, and plant winter squash and pumpkins around the base of the clump 3 weeks after the beans. The beans will climb up the flowers and the low-growing squash will shade out weeds and prevent the soil from drying out.
The flowers not only look like the sun; they need a lot of it. They grow best with about six to eight hours a day but more is even better. They can grow as tall as 16 feet, although many varieties have been developed to thrive at different heights. Flowers planted too close together will compete and not blossom to their full potential.
Sunflowers display a behavior called heliotropism when they are young–the flower buds and blossoms will face east in the morning and follow the sun as the earth moves during the day. However, as the flowers get heavier during seed production, the stems will stiffen and the mature flower heads will generally remain facing east.
Although sunflowers can be started indoors in individual peat pots, it is easiest to sow seeds directly into the soil after all danger of spring frost is past. However, where the growing season is short, sunflowers can be safely planted up to 2 weeks before the last expected spring frost.