From our Garden, Can you pick out Droopy, or I follow the sun and I’m taking my time….
|Sunflowers are a member of the aster family. The large flower head is actually an inflorescence, or composite flower, made up of two kinds of tiny florets. The disc florets are located in the center of the composite flower, and the ray florets bear the outer ring of petal-like structures. |
Ray florets are sterile, and disc florets have both male and female structures, including a single ovary that develops into a sunflower seed.
A single flower head may have up to two thousand disc florets, each with the potential to develop into a seed. If there are multiple flower heads on the same plant, the number of disc florets per head will be much lower. The disc florets open in sequence, beginning at the periphery of the disc and moving inward.
Each floret is first male, with the pollen-bearing anthers extending above the rim of the floret. Later, the style pushes up and the stigmatic lobes spread, opening the receptive surfaces for pollination. If pollinator activity is adequate, the pollen is removed from each floret before the stigma opens, reducing the chances for self-pollination.
The anatomical features of the florets of the sunflower Helianthus annuus var. macrocarpus are being studied through cooperative research involving the USDA North Central States Bee Research Lab, Madison. WI and the USDA Oilseed Research Lab, North Dakota State University, Fargo, ND.
The purpose of thesestudies is to identify and evaluate all of the structures of the sunflower inflorescence that influence honey bee (Apis mellifera L.) visitation.The sunflower inflorescence has two types of flowers on a single head or capitulum.
Typically, the outher rim is defined by pistillate, sterile ray florets. Each is composed of five united petals that range in color from cream or yellow through yellow-orange to almost red. The remainder of the capitulum is filled with hermaphroditic, protandrous disc florets. The corolla tube of each floret is comprised of five fused petals which open distally to accommodate the emerging anther tube. Five fused anthers are attached to the base of the swollen corolla by flattened filaments.
We found that migrating birds will move under the hanging sunflower head to eat the seeds and bees are the pollinators.