The large floral disk of sunflowers, jam packed with seeds, hardly needs description, but there is a lot more to this cheery bloom than meets the eye.
Ancient history & sunflowers
Sunflowers are native to North America. Recent research has shown that they were also growing in Central America way back into antiquity. There are some interesting name exchanges in primitive languages that lead archeologists to believe there were far more cultural exchanges between the two regions than was previously thought. According to researchers at the University of Cincinnati, “sunflowers were domesticated thousands of years and hundreds of miles apart” making them an interesting topic in human history. More currently, sunflowers are one of the world’s top oil producing plants. Each year, nearly 45 million tons of sunflowers are grown worldwide!
The sunflower family
Sunflowers are part of a plant family called Asteraceae. The sunflower family includes asters, artichokes, dahlias, yarrow, marigolds, endive, dandelions, and Echinacea, just to name a few. Sunflowers can be annual or perennial, depending on the variety, microclimate, and growing conditions. Some varieties grow as a single fat, hairy stalk, while others grow several branches. There are eleven species of sunflower (Helianthus annus) in California. Some dwarf varieties are only a foot and a half tall, while others can reach twelve feet!
Benefits of sunflowers
If the happy blooms and tasty seeds weren’t reason enough to add them to your garden, sunflowers also attract many beneficial insects. Honey bees, lacewings, butterflies, hoverflies, and parasitic wasps enjoy the nectar, pollen, and prey insects found on and near sunflowers. Personally, I love the tiny finches that are so fond of eating the wide, spade-shaped leaves. Local squirrels and seed eating birds can become problematic, or you can simply plant a few extras near the fence line.
Heliotropism refers to a plant’s ability to track the sun’s movement and sunflowers are masters of heliotropism. Sunflowers use phytohormones called auxins and an internal circadian clock to follow the sun across the sky each day. During the night, they turn their west-facing blooms back toward the east, in anticipation of the dawn. Scientists were surprised to discover that bringing outdoor sunflowers indoors, with a constant overhead light source, the plants still went through their east to west cycle for a few days. It was also found that certain genes tell the east side of the plants grow more quickly during the day, while the west side of the plants grows more at night. As the plants mature, this movement slows, leaving most sunflowers facing east, rather than west. The reason? Scientists found that eastward facing flower heads (capitula) heated up more quickly than their westward neighbors. This added warmth attracted FIVE TIMES more beneficial insects, for better pollination and pest protection! [I have to assume that this directional movement is flipped in the southern hemisphere.]
Sunflowers and children
Sunflowers grow quickly and often to impressive heights, which makes them an excellent choice when gardening with children. In fact, if you plant your sunflower seeds properly, you can create a fort, a maze, or a magic castle right in your own back yard! Or, to watch germination as it occurs, you can place sunflower seeds inside a clear glass with a dark colored sponge. Place the seeds between the glass and the sponge and add water. Before you know it, the magic happens! Then take your sunflower sprouts and add them to a salad or plant them in the garden! In either case, they make a healthy snack and provide your children with a sense of ownership.
How to grow sunflowers
Most sunflower plants are grown from seed. A few species also propagate using creeping roots, which makes them a noxious weed in some agricultural areas. Sunflowers need lots of sun, water, and nitrogen, but they are less picky about soil than many other plants. Seeds can be started in cell flats or other small containers and then transplanted, or they can be directly sown into the garden or landscape, after the last chance of frost has passed. Seeds should be planted one inch deep and watered daily until they sprout. After they have sprouted, plants will need an inch of rain or irrigation each week, depending on the weather. For optimal growth, space your sunflower 2 ½ to 3 feet apart. Dwarf varieties only need 6 inches. Seedlings often need protection from birds, squirrels, slugs and snails. Sunflowers can take up to 3 months to reach full size. Sunflowers need lots of nutrients, so adding aged compost to the planting area will help them to get a good start. They do, occasionally need staking.
Sunflower seeds contain a chemical that is toxic to grass plants, so you should harvest the seeds before they start falling on your lawn or near other members of the grain family (Poaceae), such as corn, millet, wheat, barley, or bamboo. You can also plant sunflowers much the way Native Americans did, using the Three Sisters Method, by replacing corn with sunflowers. The squash or melon leaves will shade the ground around your sunflowers and pole beans will climb the stalks and provide a nitrogen boost before they go to seed themselves.
Sunflower pests & diseases
Sunflowers tend to be sturdy plants that fend for themselves rather well. Keep a look out for ant trails going up the stalks that can indicate an aphid problem. Sticky barriers can be used to block the ants, which makes the aphids more vulnerable to their natural enemies. Other sunflower pests include dried fruit beetles, cutworms, carrot beetles, some foliage-feeding caterpillars, leaf beetles, spider mites, thrips, and the dreaded sunflower bud moth. Fungal diseases, such as crown gall, downy mildews, powdery mildew, rust, and Verticillium wilt can be a problem, but this occurs more in agricultural fields than in backyard gardens.
Once your sunflower head has reached full size, it will probably be bent over and surprisingly heavy. If you stroke the face of the flower head with your hand, dozens of tiny dried bits (pappus) will fall away. Personally, I give all my sunflowers a quick rub to dislodge potential pests and to remove these bits. Before removing the head from the stalk, use your fingernail to nick out a few seeds and open them up. Are the seeds plump? If not, give them some more time. You certainly don’t want to harvest a head of empty shells! Seeds have normally reached maturity around the same time the petals start to fall from the flower. You can protect immature heads from birds with netting or large paper bags. Once the seeds have reached maturity, cut the stem an inch or two below the flower head. Seeds can be allowed to dry in the head, or they can be rubbed loose over a newspaper or old sheet. Be sure to blow away any chaff that may harbor pests or disease. I always save several of the largest, healthiest looking seeds for next year’s crop. After that, allow seeds to dry out completely before storing in an airtight container. You can also salt and/or roast your seeds. If you suspect seed pests, freezing your sunflower seeds will kill off any eggs that may be lurking in the shells. Sunflower seeds stored in the refrigerator or freezer are good for a year, while raw seeds stored at room temperature are only good for 2 or 3 months. Roasted, shelled seeds have a shelf life of 3 to 4 months, and unshelled roasted seeds can last 4 to 5 months.
Sunflower oil can be used as a horticultural oil, but I definitely prefer it as sunflower butter on toast or in place of peanut butter in cookies. Yummy!
One variety, the giant whorled sunflower (Helianthus verticillatus) was first seen in 1892. Then it was believed to be extinct until 1994 when it was discovered by Vanderbilt University student, Jennifer Ellis. The giant whorled sunflower is currently listed as an endangered species and is only found in Alabama, Georgia, and Tennessee - the birthplace of the sunflower species.
In the 1500s, Spanish conquistadores banned the use of sunflowers in Mexico, believing that they were an aphrodisiac.
Add some sunflowers to your garden today! (No matter what the Spaniards said!)
You can grow a surprising amount of food in your own yard. Ask me how!
Help The Daily Garden grow! Click below.