Agriculture Reference
In-Depth Information
Sunflower seeds
WHAT YOU'LL NEED
• 10 to 15 healthy plants
• bags big enough to contain flower heads, if more than one variety is being grown in a given season
POLLINATION NOTES
Sunflowers are outcrossers and are visited by many insects. A large sunflower
flower head can contain as many as 8,000 individual flowers, each of which is open for about two
days. Anthers release pollen on the first day; on the second day, the stigma protrudes and is ready to
receive pollen. All individual flowers open over the course of five to 19 days. A typical flower head
has dried flowers along the outside edge, then a circle of flowers open for pollen reception, then a
circle of flowers giving off pollen, then some unopened flowers. Some varieties are self-fertile, which
means insects can simply carry pollen from one individual flower to another on the same flower head.
Other varieties are self-infertile and are therefore obligate crossers. To prevent crossing in small-scale
sunflower growing, an isolation distance of 1000 ft. (300 m) is necessary. Large-scale growers use
isolation distances of several miles. Another method is hand pollination. This is time-consuming but
relatively easy to do: cover unopened flower heads with a bag or insect netting and close tightly. To
pollinate, remove bags and rub flowers against each other daily. Beware of pollinator insects while do-
ing this! To intentionally cross two varieties, simply grow them next to each other.
The individual flowers are clearly visible on large sunflower flower heads.
