Regional Gardening Reports :: National Gardening Association

In the Garden:
March, 2007
Regional Report

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The Philadelphia Flower Show mythically transported visitors to Ireland this year, with the help of leprechauns.

Flower's Power: Over Us and Nature's Smaller Creatures

Yes, I spied the leprechaun -- leaf-covered, lithe, bristly shock of hair, Star Trek ears -- tickling daffodils and darting among muslin trees in the Ealain Wood at this year's Philadelphia Flower Show. Hope you did, too, in Legends of Ireland -- the main exhibit of Tir-Na-nOg, the mythical land of the young!!!

So many cultivars of oxalis, the shamrock plant. Heathers tucked in exhibit nooks and crannies. Add toe-tapping Irish tunes, faeries, cairns, castle ruins, Celtic-inscribed stones, green/white floral displays. The only thing missing is brimming mugs of Guinness.

Flower Power stirs us from the winter doldrums to hop buses, trains, and planes to travel hundreds, even thousands of miles. Flower Power is also integral to environmental balance in our yards.

Follow Mother Nature's lead and mix it up in the landscape, advised pest management experts at Bartlett Day at the Philadelphia Flower Show.

"Diversity is Mother Nature's way of preventing catastrophic loss," said Dr. Michael Raupp. Making his point, he asked us to look left and right at our neighbors in a "rainbow" audience -- from the young to boomers to retirees of many colors, shapes, and sizes. Our genetic differences make us stronger as a species in the face of microbes, diseases, environmental imbalances.

So it is with plants in the landscape, said Raupp, seconded by Dr. Paula Shrewsbury of the University of Maryland. "The more plant diversity and structural complexity, the better," said Shrewsbury. The ideal is a highly diverse yard and garden with myriad plant species: understory trees, shrubs, herbaceous and flowering plants, ground cover and turf, ranging from midsize to soil-hugging.

A richness of species and structural complexity means more insects, Raupp added. That's a good thing, explained Shrewsbury. Diversity restores ecological function -- the natural balance supporting favorable habitats for natural enemies. In a study of azaleas infested with azalea lace bugs, the more complex the landscape, the fewer lace bugs found sucking the leaf chlorophyll and plant juices. (Infested leaves look stippled with white spots; the undersides have dark bumps.) A more diverse, complex landscape is hospitable to an abundance of insects including natural enemies -- both predators, and prey, Shrewsbury explained. In the azalea study, more predators survived in the diverse landscape and they feasted heartily on lace bugs (as well as other prey).

Why more insects? More plants means a smorgasbord of food! Researchers grew large composite Shasta daisies and small coriander flowers near azaleas; peonies, bunch grass, and flowers near cutworm-infested turf. The flowers supplied nectar and pollen that nurtured omnivore activity, Shrewsbury said. "So predators stay and eat other prey in the richer, more diverse landscape."

Structural diversity enhances species diversity by providing microclimates and refuges where insects nest and reproduce. Various layers attract and support different insects. For example, ground cover encourages ground beetles and spiders.

"If we add flowers to our landscapes, natural enemies will come," Shrewsbury emphasized. Among her favorites are threadleaf coreopsis, alyssum, and small sunflowers. For pest management, she and Raupp recommend the natives, such as coreopsis, eupatorium, mountain mint (Pycnanthemum incanum), and horse mint (Monarda punctata).

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