Published on 04/07/97

Tree Flowers Have Come a Long Way

The spring you see and smell had its roots in an ancient forest.

Georgia's trees tell many stories of success and failure, an ecological heritage that has sheltered humans from climate and poverty.

Long ago on a continent far away was a warm, humid forest. In it were many kinds of plants, each locked into fierce competition to collect and control resources. The successful ones could grow, defend themselves and reproduce. Only successful plants survived.

To succeed, a tree had to reproduce. One successful reproduction system was "cone bearing." Early in tree history, many forms of spirally designed cones were produced on branches and along trunks for seed production.

Large, woody cones held seeds where the tree could nourish the embryos, and where the wind could catch seed edges and wings for distribution across the forest.

These trees also produced small, fragile cones that held pollen. When these cones mature, they rupture and release millions of pollen grains.

Warm, sunny days with low relative humidity help release pollen. The air around the small cones buoyed up the pollen as the wind swirled it around the canopy tops.

Only those trees whose crowns were up in the wind could distribute pollen and seeds successfully to new sites. Young trees had to survive for years beneath taller light- and wind-blocking trees for their place in the sun.

For little trees, the dungeons or understories of these forests were hard to escape before competition and pests eliminated them.

One day among the dinosaurs, a genetic experiment was set up. A small tree, growing beneath much larger and taller brethren, generated a flower. It wasn't derived, as cones were, from woody twigs but from modified leaves.

This tree flower was designed not for the wind, but to attract insects, birds and small mammals.

In this experiment, all the tree traits (and all the resources required for these traits) needed to use wind power for reproduction could now be used instead to induce animals to move pollen. This required new parts and designs. Trees generated new colors, shapes and smells as enticements.

The showy tree flowers we see today are from this lineage. Their bright colors are a stop sign for animals to explore, maybe receive a treat -- and fertilize the tree by carrying pollen.

The wind was left behind in the forest top, along with the many wind-pollinated flowers of other tree species.

Across the plant kingdom, the showy flowers have been successful in many places. But the miniaturized wind-pollinated flowers have become even more successful.

The forests, savannahs and prairies of Earth are covered with wind-borne pollen producers. From some perspectives, showy flowers are relics of a genetic experiment that failed. People have been able to extract great value from these showy-flowered species.

For creatures that use sight and smell, tree flowers can be great attractants and a necessity. Trees have come a long way from a simple, small, magnolia-like flower in the bottom of a forest to the widely diverse tree-borne flowers we see outside our windows.

Surrounded by trees, it's easy to overlook their value. It's also easy to ignore their great biological history. But deep in the past, the story of trees contains many lessons.

Kim Coder is a forester with the University of Georgia Warnell School of Forestry and Natural Resources.