Mongolian Giant Sunflower

Sunflowers are widely adapted to a variety of climates and are especially tolerant of cold temperatures.  Sunflowers will flourish in a wide variety of soil types, from clay to sandy, so long as sufficient nitrogen is available throughout the growing season.  The water requirements of sunflowers are similar to those of other field crops.  Plants should be irrigated if drought occurs within 20 days of pollination as this period is especially critical for seed development.

After danger of frost has passed, sow seeds 6" apart, 1/2" deep in rows 36" apart.  Germination will occur in 6-10 days.  Thin to one plant every 24" once seedlings have reached six inches tall. Can also be started indoors 4 weeks before the average last frost date.

Transplant outdoors after danger of frost has passed.  Plants should be spaced 18-24" apart to provide for ample air flow.

Sunflowers are susceptible to a number of common diseases including verticillium wilt, mildew, leaf spot, and rust.  However, the extent of these diseases is usually not of consequence to the home gardener.  Ensuring adequate airflow by thinning plants to the recommended spacing will reduce the incidence of disease and cultural practices such as crop rotation, tillage and removal of plant debris in the fall will limit its spread.

Sunflowers make great cut flowers. They are long-lasting and have a bright, cheerful appearance that adds a cheerful touch to any bouquet or arrangement. Sunflowers are also easy to care for, and can last up to a week when cut and placed in a vase with fresh water. When harvesting fresh cut flowers, cut the main head just before it blooms to encourage additional blooms on side shoots. Harvesting flowers in the morning will prevent premature wilting.

CONSIDERATIONS:

Sunflowers are outbreeding plants, relying on bees and other insects for their pollination. Varieties may be self-compatible or self-incompatible, meaning that pollen must be moved from one plant to another. Plants of different varieties must be isolated by 1/2 to 3 miles, depending on the population size and insects in the area, to maintain varietal purity. Hand pollination can be performed by bagging heads and rubbing the flowers of adjacent plants together each day for 10 consecutive days. Heads should be re-bagged after pollination to prevent pollen contamination and predation by birds.

HARVESTING SEED:

SEED LONGETIVITY:

Sunflower seeds can remain viable for up to five years if stored in a cool, dry place.