Nature's Secrets

Lowman: A thousand shades of green herald spring

May 2, 2011 

"In every walk with nature one receives far more than he seeks."

John Muir

Like a baby's soft skin, the new foliage of spring is delicate and breathtaking as it unfolds to signify a rebirth of the natural world.

A leaf lover for many decades, I can vouch for the existence of thousands of green hues in the botanical world, each unique.

The sun-drenched lime greens of live oak catkins indicate subtle signs of a Florida spring. The cinnamon greens of unfurling magnolia leaves announce spring in Georgia. The dazzling array of dogwood, hornbeam, beech and oak greenery - interspersed with the electric pinks and reds of budding maples and redbud - signify spring in North Carolina.

Further north in New England, fuzzy green fiddleheads unfold into fabulous spring fern fronds along the roadsides. Halfway around the world, the blue-greens of young eucalyptus leaves signify spring in the Australian outback (but in October!); further north, the red floral globules of flame trees usher in Queensland's tropical spring.

The science of monitoring nature's seasonal activities is called phenology. In temperate climates, warming temperatures and longer days trigger budburst followed by leafing, flowering, fruiting and other phenological events. The youthful greens of spring foliage transition into shade-giving darker green canopies of summer, as leaves expand and age. Mature leaves are often riddled with holes, reflecting the seasonal cycles of insect pests whose phenology was perfectly timed to feast on the softer, less toxic, new foliage.

With their abundant leafy canopies, trees perform an important task that nothing else on Earth can replicate: They produce energy from the sun that is transformed into sugars that drive the food chains of our planet. But the efficiency level of these green leaf-factories is approximately 1 percent, with the remaining 99 percent expended to maintain the factory. Half of that maintenance involves transpiration, whereby water moves from the roots all the way up to the leaf-factories.

This continuous strand of water rising up through the sapwood goes against gravity and in some trees may travel as high as 350 feet. It has been estimated that a corn stalk will lift over 400 pounds of water in a brief growing season, and that 6.5 tons of water passes through an acre of grass on a summer day. Spring greens are nature's way of announcing that these energy factories are resuming operation.

At the Arnold Arboretum in Boston, average spring flowering dates have advanced by eight days with the onset of warmer temperatures. Similar earlier patterns have been documented in England. Throughout the country, citizens can monitor their local budburst and compare changes over time ( www.budburst.org). Long considered reliable indicators of spring, plant budburst and leafing events are shifting in response to climate change. In North Carolina, could such earlier flowering trigger our proverbial "spring fever" in January instead of in March?

Meg Lowman: www.canopymeg.com

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