Charles T. Behnke
Sunflower is the common seed name for the
genus Helianthus. The sunflower is native to North America,
and was used by early North American Indians for food and pressed to
make hair oil. Meal from processed seed has been used for livestock
feed. Today, whole seeds are used for oil, bird seed and snacks. The
seeds are a rich source of calcium plus 11 other minerals. The 50
percent fat composition is mostly polyunsaturated linoleic acid.
As a garden plant, the sunflower is
valuable for forming a background screen. A rapid grower, it reaches
a height of 8 to 12 feet in rich soil.
This rapid growth could cause competition
with other garden plants, especially by shading. Sunflowers can be
planted between groups of shrubs, particularly where these form a
background. For smaller gardens, the multi-branched species are more
suitable. Dwarf forms of 24 inches in height make a spectacular bed
When growing sunflowers for bird food or
human consumption, select the confectionery types over the oil
Sunflowers do best when grown on soils with
adequate water-holding capacity, internal drainage and proper
fertility. They will tolerate a wide range of soil types; however,
one that is too high in nitrogen encourages excessive plant growth
that will check maturity of the flower heads. Adequate levels of
phosphorus and potassium are recommended, and, as with any garden
activity, frequent soil tests are recommended to get good results.
The plant's roots go deep and spread extensively, so the sunflower
can withstand some drought and nearby cultivation. Sunflowers should
not be water stressed during the critical period; about 20 days
before and after flowering.
Plant seed into moistened soil one to two
inches deep, but no deeper than three inches. Space seed 12 inches
apart in rows spaced 2 to 2 1/2 feet apart. Plants grown for large
heads should be spaced farther apart or scattered around the garden.
In Ohio, planting can take place from early
to mid-May. Seed bed soil temperature must be between 42 and 50
degrees F with temperatures above 50 degrees F preferable for
germination to occur rapidly. Depending on variety and environmental
factors, germination will occur in 7 to 12 days. Plants will mature
in 80 to 90 days.
For the home situation, seed can be started
in four-inch peat pots and transplanted outdoors. Transplants may
grow taller and flower sooner than seed started plants. They should
start to flower in ten weeks.
Weeds can be a problem for sunflowers. Weed
control is practiced for the first four to five weeks after seed
emergence. For the home garden, hand weeding and mulching are the
Diseases and Pests
A common disease of sunflowers is
Sclerotina or white mold, which causes stalk and head rots.
Disease spores can live for many years in the soil. Other common
diseases are downy mildew, rust and verticillium wilt. Sanitation
and crop rotation should be considered for control in the home
The sunflower head moth is the major insect
pest. The moth attacks at flowering time with the larvae feeding on
floral parts and tunneling through developing seed. Aphids and
whiteflies also can be a problem.
Birds can be troublesome near harvest time.
Seeds are exposed and the large flower head serves as a feeding
perch. To deter birds, use frightening devices and human activity in
the immediate area before damage is expected. Flower heads can be
covered with plastic netting or cheesecloth.
Harvest begins in mid-September and can run
into October. A check of the flower head will indicate maturity;
florets in the center of the flower disk are shriveled, heads are
downturned, and a lemon yellow color is on the backside. Pull a few
seeds and split them with a knife to check if seed meat has filled.
Poorly filled seeds may be due to a lack of pollinating insects.
To harvest, cut the seed head with about a
foot of stem attached and hang in a warm, dry, well-ventilated,
rodent and insect-free place. A paper bag with holes or cheesecloth
can be placed over the heads to catch falling seeds as they drop
during drying. Seed heads can be allowed to ripen on the plant, but
cheesecloth or nylon netting will be needed for bird protection.
Once the seed is dried, it can be rubbed easily from seed heads.
Humidity levels must be kept low to prevent spoilage.
Raw mature seeds may easily be prepared at
home by covering unshelled seeds with salted water (2 qts. of water
to 1/4 to 1/2 cups salt). Bring to a boil and simmer two hours or
soak in a salt solution overnight. Drain and dry on absorbent paper.
Put sunflower seeds in a shallow pan in a
300 degree F oven for 30 to 40 minutes or until golden brown,
stirring occasionally. Take out of oven and add one teaspoon of
melted butter or margarine to one cup of seeds. Stir to coat. Put on
an absorbent towel. Salt to taste.
Common Sunflower (H. annuus) -
Includes the cultivars H. bismarkianus's, single yellow
flower, 6 to 8 feet tall; H. citrinus, primrose yellow
flowers, 6 to 8 feet tall; H. giganteus, Russian Giant,
large, single yellow flower grown mainly for seeds, 10 to 12 feet
Silverleaf Sunflower (H. argophyllus)
- Stems and leaves covered with silky gray down, especially on
younger growth. Flowers golden with purplish brown center, plants 5
to 6 feet tall. Silvery leaves used in fresh and dried flower
Cucumberleaf Sunflower (H.
debilis) - Four-foot plants with multiple branches. Excellent
for cutting. Three-inch flowers have a purple disk and yellow rays.