Growing Sunflowers HYG-1228-92 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.
Uses 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 by themselves. When growing
sunflowers for bird food or human consumption, select the confectionery types
over the oil types.
Culture
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. 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 best
methods.
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 garden. 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.
Harvesting
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.
Roasting Seeds
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.
Sunflower Species
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 tall. 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 arrangements. Cucumberleaf Sunflower (H. debilis) -
Four-foot plants with multiple branches. Excellent for cutting. Three-inch
flowers have a purple disk and yellow rays.
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