July: More than meets the eye

By DAN ZARLENGA
Missouri Department of Conservation

As the month of July unfurls its warm and sunny days, it welcomes a parade of brilliant flowers. One of these is the black-eyed Susan. It’s a flower that really packs a punch, thanks to a special hidden power. Hidden from us humans, that is. With these flowers, there’s more than meets the eye.

Black-eyed Susan blooms annually, with flowers that are around four inches across and may appear solitary or in loose, open clusters. The daisy-like blossoms can be recognized by their somewhat thin bright yellow or orangish rays. The disk in the center of the flower is no doubt the “black eye;” it is domed, dark and chocolate-brown in color.

You can find black-eyed Susans in a variety of places: upland forests, upland prairies, glades, pastures, old fields, railroads, roadsides, and many open, disturbed areas. Because of their hardiness and versatility, these flowers make excellent prospects for native landscaping, and they are popular for roadside beautification projects.

Black-eyed Susans tolerate heat and drought conditions well, and so they are one species of flower that tends to thrive in the hot summer months of July and August.

BEES SEE THEM DIFFERENTLY
Lo and behold these black-eyed flowers are especially attractive to creatures with an eye for violet. For example, many species of bees see very weakly at the red part of the rainbow but are much more sensitive toward the blue end of the spectrum, and to the frequencies of ultraviolet light.

Ultraviolet radiation lies between visible light and X-rays along the electromagnetic spectrum. A typical human can see the blue end only to about 400 nanometers, while a bee can detect a hundred nanometers further to 300 nanometers, well into the ultraviolet. Many species of butterflies can also perceive UV light.

Bees and butterflies are highly prolific pollinators. Black-eyed Susans are one of the species of flowers that have developed special coloring to take advantage of that. They reflect and absorb UV light in patterns to attract these desirable insects. Where we humans see only yellow, UV savvy pollinators see a powerful beacon.

When observed beyond the visible blue part of the spectrum, black-eyed Susans reveal prominent UV patterns. From the tips of the petal and extending to the middle of the flower, a black-eyed Susan reflects ultraviolet and is very bright to UV viewers. This transitions to the center which absorbs ultraviolet light and is very UV dark.

The result is a bullseye design invisible to humans but readily perceived by bees and butterflies. The bullseye forms a landing zone, ushering pollinators toward the central “black eye” rich with nectar and pollen. The insects indulge in the nectar, and the pollen sticks to their bodies and feet so they can carry it off to other black-eyed Susans.

It’s all an incredible example of how different the world looks, depending on who’s viewing it! To us, these “Susans” may have black eyes. But seen by bees and butterflies, the same floral ladies have eyes of radiant violet. That’s the beauty of these flowers our eyes will never meet.