Friday, August 8, 2014

Hummingbirds and sunflowers...

We often think of hummingbirds sipping nectar from red, tubular-shaped flowers, but if you've ever spent any time around sunflowers, you know they are a favorite of hummers too...

A juvenile male Ruby-throated Hummingbird sips nectar from a disc floret on a sunflower.
...and there is a reason hummingbirds love sunflowers. If you look closely at the center disc of a sunflower (or a black-eyed susan, zinnia, or any other daisy-like flower), you'll find hundreds of tiny tubular shaped flowers (called florets). These little florets are perfect flowers that each contain drops of nectar.

Hummers have precise eye-bill coordination to be able to hover and drink from such a tiny cup!
A happy hummer!

What is a composite flower?
A composite flower looks like one big flower, but it's really an inflorescence (or grouping) of hundreds of tiny flowers called florets. Daisies, black-eyed susans, purple coneflowers, zinnias, asters, dandelions, etc., are all composite flowers.  There are two types of florets in a composite flower:

Ray florets - are located along the perimeter of the flower head and form what look like petals that "radiate" out from the center (which is why they are called rays). Ray florets contain only a pistil (the female reproductive organ).

Disc florets - form the center disc of the flower head. Disc florets have a stamen and a pistil, so they are considered tiny, perfect flowers. Hundreds of disc florets create the flower head.

("Perfect" flowers contain both reproductive organs--a pistil (the female reproductive organs) and stamens (the male reproductive organs; the anthers contain the pollen). Lilies, daffodils, petunias, etc. are perfect flowers.)

Cross-section of a composite flower
When you realize that a composite flower is made up of hundreds of florets, all of which are tiny tubular flowers filled with nectar, it's easy to see why hummingbirds love sunflowers!

When the florets are finished blooming, and the seeds ripen (in the ovary of the pistil), American Goldfinches and Northern Cardinals take over...

An American Goldfinch eats sunflower seeds in the late evening light.

(I photographed these birds in my friend Sarah's beautiful garden.)