All About Sunflowers
Sunflowers grow best in locations with full sun. They are remarkably tough and will grow in any kind of soil as long as it is not waterlogged. They do fine in soils that are slightly acidic to somewhat alkaline (pH 6.0 to 7.5). Once sunflowers get started, they can tolerate drought as befits plants whose ancestors grew happily in dry prairie regions. They are so easy to grow that they often plant themselves, springing up unbidden beneath a bird feeder.
Sunflower seed, leaves and stems emit substances that inhibit the growth of certain other plants. They should be separated from potatoes and pole beans. Where sunflower seeds are regularly used as bird feed, toxins from the accumulated seed hulls eventually kill the grass below. Harmless to animals or people, the toxins eventually biodegrade in the soil.
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PLANT HISTORY
Contemporary sunflowers trace their ancestry to plants found at archeological sites dating from 3,000 BC. While they grew abundantly on the Great Plains, sunflowers were first purposely cultivated by Native Americans in the Southwest or Mississippi River valley area as a source of medicine, fiber, seeds, and oil.
When the European settlers arrived, they immediately recognized the value of sunflowers and sent seeds back to Europe. There they found a place in English cottage gardens and even Van Gogh's paintings. However, it was in Russia that the sunflower became a major agricultural crop. They provided a source of oil that could be eaten without breaking church dietary laws. Early in the 20th Century, Russian growers spearheaded the breeding and selection for disease resistance and high oil content. In the 1960s, the U.S. began sustained commercial production of oil seed cultivars to produce vegetable oil.
Long beloved as part of the rural landscape, sunflowers have been embraced by gardeners as an ornamental plant relatively recently. Responding to this interest, breeders in Germany, Japan and the U.S. have developed types particularly suitable for home gardens.
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SEEDS OR PLANTS?
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. Sunflowers can take a chill or two. Where growing seasons are long, it is best to wait until the soil temperature reaches 55 degrees to 60 degrees F.
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CULTIVATION
To plant in rows, space seeds about 6 inches apart in a shallow trench between 1 and 2 inches deep. In sandy soil, 2 inches deep is better. Cover and keep watered until seeds sprout in 7 to 10 days. When first true leaves appear (the second set of leaves); thin plants to about 2 feet apart. Depending on the variety, sunflowers will mature and develop seeds in 80 to 120 days. Sow a new row every 2 to 3 weeks to enjoy continuous blooms until the first frost.
For maximum seed production space rows 2 to 3 feet apart. Use traditional, tall, seed-producing varieties such as 'Mammoth' or 'Paul Bunyan Hybrid', 'Aztec Gold Hybrid', or 'Super Snack Hybrid'.
To grow smaller flowers for bouquets, space plants much closer together?about 6 inches apart in Maine, or as close as 2 inches in dry places like Arizona. Skip fertilizing. The plants will be much smaller, with fewer branches, but the stems will be longer and flower heads a good size for arrangements.
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GROWING TIPS
Sunflower roots spread widely and can withstand some drought. However, it is best to water them regularly during their most important growth period which is about 20 days before and after flowering. Deep, regular watering helps encourage root growth, which is especially helpful with taller sunflower varieties bearing top-heavy blooms.
Sunflowers do not require fertilizing. However, because they grow vigorously (they can easily grow 6 feet in just 3 months), it's a good idea to add some slow-acting granular fertilizer to especially poor, thin soil. The better their diet, the larger the flowers. Do not overdo the nitrogen because that will delay flowering. Spreading a 2- or 3-inch mulch layer of some kind of organic material on the soil will reduce moisture loss through evaporation and discourage weeds.
While a few sunflower varieties do not need any staking, it is a good idea to support plants that grow over 3 feet tall or are multi-branched. Their branches are fairly brittle, especially at the points where they join the stems. Shallow rooted and weighed down with many large flower heads, plants are vulnerable to summer winds and rain. Tie the plants loosely to stakes with lengths of cloth or other soft material as needed.
Birds and squirrels can be a problem when seeds ripen and harvest time approaches. If you do not plan to use the seeds, it is fun to watch wildlife enjoy the bounty. You may want to cut the flower heads off and lay them out in the sun to dry and provide easier access to wildlife. Conversely, to deter birds and squirrels, barrier devices are most effective. As seed heads mature and flowers droop, cover each one with white polyspun garden fleece. It will let light and air in and keep critters out. Also try cutting away the few leaves that are closest to the heads to make it harder for birds to perch and feed.
Deer will readily eliminate a sunflower patch. As they favor the new, tender leaves at the top of the plants, a 36-inch chicken wire barrier supported by 6-foot bamboo stakes should keep them at bay. Simply raise the wire as the plants grow.
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INSECTS & DISEASES
Sunflowers are virtually as care free as their smiling faces suggest. However, they are sometimes infected with fungal diseases such as mildews and rusts. Downy Mildew causes mottling and pale areas on upper leaf surfaces and a fuzzy mold growth on their undersides. Eventually the leaves wither and die. The oldest leaves are usually infected first. Downy mildew is most likely to occur on cool damp nights and warm humid days. It spreads by means of tiny spores carried to plants and soil by wind and rain or transmitted by garden tools. It will not kill a mature plant; it just mars its appearance.
Rust appears on upper leaf surfaces first as yellow or white spots that turn brown or black. Puffy blisters then appear on the undersides. The disease may spread to stems and flowers causing distorted growth. Rust sometimes spreads to the cultivated sunflowers from weeds such as wild mustard, shepherd's-purse, pigweed, and lamb's-quarters.
If fungal diseases are spotted early, spraying with a general garden fungicide as directed on the product label can protect healthy foliage. Remove and destroy seriously infected plants. Keep the area weeded and clean up plant debris from the garden in the fall. Disinfect tools by dipping them in a solution of 1 part household bleach to 4 parts water. Keep your hands clean, and do not handle plants when they are wet.
A small gray sunflower moth sometimes lays its eggs in developing sunflower blossoms. Its larvae are greenish-yellow with 5 brown stripes down their backs. They feed in the flower and destroy seeds, creating a mass of webbing and debris. Pick the worms from the plants and mash them between your fingers or drop them into a plastic bag for the trash. If lots of plants are infested, spray or dust the flowers with a product containing Bacillus thuringiensis (Bt) as soon as you see the larvae. The larvae will eat the bacterium and soon die. Because sunlight and rain rapidly inactivate Bt, respray as directed on the product label.
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HARVEST TIPS
In the early fall, check flower heads for signs of maturity. The reverse side turns from green to a yellow-brown. Large heads will nod downward. A close look will reveal the tiny petals covering the developing seeds have dried and now fall out easily exposing the tightly packed mature seeds.
To harvest the seeds ahead of the birds and squirrels, cut off the seed heads with a foot or so of stem attached and hang them in a warm, dry place that is well-ventilated and protected from rodents and bugs. Keep the harvested seed heads out of humidity to prevent spoilage from molds and let them cure for several weeks. When the seeds are thoroughly dried dislodge them by rubbing two heads together, or by brushing them with your fingers or a stiff brush. Allow the seeds to dry for a few more days then store in airtight glass jars in the refrigerator to retain flavor.
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RECIPES & STORAGE
Sunflower seeds are rich in vitamins, proteins, and minerals, as well as linoleic acid which helps the body metabolize fats properly. They contain about 24 to 27 percent protein, only slightly less than an equal weight of ground beef. Furthermore, sunflower seeds contain about twice the iron and potassium and about 4 times the phosphorus of beef. Raw sunflower seeds also contain vitamins B and E, and a dash of vitamin A. Sprouted, they also contain vitamin C.
Use the seeds for snacks, alone or mixed with raisins, dried fruit chips, and nuts. Add hulled sunflower seeds to salads and use them in fruit or vegetable recipes. Substitute sunflower seeds for nuts in baking.
To toast the seeds to enhance their flavor, lightly brown them in a skillet over medium-low heat for about 10 minutes, or on a cookie sheet in the oven at 350 degrees F for about 10 minutes.
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