Helianthus annuus: (A) Sunflowers are impressive both in the field and in the vase, and the seeds make for pleasant eating; at least the birds think so!
CULTURE: All sunflowers do best in areas with full sun. Sow seeds April through May. Optimum soil temperature: 65-75°F. Days to germination: 7-14. Sow 1/2 inch deep, 3-4 inches between plants, and 30 inches between rows. Thin to 12-18 inches, leaving the strongest plants. To promote deep roots and strong stems, water deeply but infrequently. One to two cups of our complete fertilizer per 10 row feet in the spring is adequate for the year. Over fertilization may cause stems to break in the fall. Germination code: (4)
DISEASE AND PESTS: Watch for cutworms and weevils in the spring. A Pyrethrin powder, dusted or sprayed, works well for control. Avoid wetting the foliage to help prevent rust. Bird netting or flash tape will discourage birds.
HARVEST: Cut flowers in the morning just after they open. Use a clean knife, a clean vase, and a few drops of chlorine bleach in the water, along with Floralife Cut Flower Food (ZFE272), to help maintain freshness. Cutting the mature central flower head will promote side-shoot flower production. Black-hulled sunflower seeds are a favorite with seed-eating birds. Harvest the heads when the bracts begin to shrivel, and hang the flowers upside down in a barn or shed. For seed-eating gardeners, gray and white striped sunflower seeds are the leading choice for munching raw, or roasted and salted. Harvest these the same way.
SALTING: When dry, rub the seeds off the heads and soak overnight in 1 gallon of water with 1 cup of salt added. Drain, and then dry in a 250°F oven for 4-5 hours and store in an airtight container.
GERMINATION CODE: Given at the end of each description to give you specific information.
(1) Germination occurs between 70-85°F and within 6-15 days. Sow indoors and cover lightly.
(2) Needs a period of pre-chilling. Mix seeds with moistened peat moss and place in plastic bag. Seal and place bag in an area where the temperature is around 60°F for 2-3 days. Then place in the refrigerator for 30-90 days. After pre-chilling, place seed on sterile seedling mix and cover lightly. Germination may take up to 30 days.
(3) Needs darkness to germinate. Remove cover as soon as germination occurs.
(4) Direct sow in the garden as soon as the soil warms to at least 55°F.
(5) Germination may be slow and erratic. A fluctuating temperature of 75°F during the day and 50°F at night may help.
(6) Needs at least 12 hours of light per day to germinate. Press into the medium but do not cover. Keep moist.
Note: For those varieties that indicate a (1) or (6), a very light covering of vermiculite will allow adequate light to the seed and keep it uniformly moist.