Celebrations of Pittsburgh's big anniversary are cropping up all over, most recently at Silver Eye Center for Photography with "250 Years of Plants: Botanical Works by Regional Photographers."

What strikes one first is the diversity of interpretation the 16 invited photographers have brought to their subject. This is not a scientific assemblage, nor a historic review, but rather an artists' garden, and one designed rather than cultivated.

The 49 images are for the most part contemporary, plucked from the photographers' imaginations to provide the "congratulatory photographic bouquet" for the city suggested by co-curators Linda Benedict-Jones, Silver Eye executive director, and photographer/naturalist Paul g. Wiegman.

A nod to the past is made by including three circa 1930 hand-colored images of lushly formal Pittsburgh gardens of the Hunt, Pontefract and Semple families, from the Hunt Institute for Botanical Documentation, and in programming.

But then fast-forward.

To Stephen Y. Lai's sensual "poppy," abstracted in close-up to shibori-like folds of glistening flame red, or his confounding viewpoint, from above, of an atypically pigmented "jack-in-the-pulpit."

Or to Tim Fabian, who treats commonplace plants -- "Dandelion (Taraxicum)," "Indian Hemp (Dogbane)" -- as design elements, articulating structural quality and calling attention to the intricacies of the humblest.

Claudia Giannini cleverly references herbarium sheets through careful compositions that display both species characteristics and intrinsic beauty, as in "Tussilago farfara (Coltsfoot)," which she notes was introduced here from Europe as a medicinal plant.

Sue Abramson weaves memory and memorial -- a time honored role for plants -- throughout "Kevin's Lettuces," five one-of-a-kind photograms with circular matting that calls to mind globes or crystal balls. The images were made from garden lettuce, planted by her late husband who died before the seeds sprouted. Abramson harvested and pressed the leaves, and resurrected them for this piece. Their order, from vertically aligned sprout to tousled whorls, suggests the passage from spring to fall, from birth to death.

John A. Fobes' Polaroid film emulsion lifts, also one-of-a-kind works, are technical tours de force involving interrupting the film's development at a critical moment and expertly applying it to watercolor paper. His five images, including "Norway Maple Seeds" and "Japanese Nettle," have a delicacy reminiscent of painting on silk. Benedict-Jones says she's never seen this difficult process executed as well. "To get any one to work is a minor miracle," she adds. "To get 16 to work on one sheet of paper is virtually unheard of." But Fobes achieved that in "Hackberry Leaves and Elm Seeds."

Whimsy and humor are present, witness the "as found" image of "Wall Grass" by Dan Mohan, or the interpretation emphasized by composition and by title -- "Duck, Duck, Goose, Moss in Bloom" -- of a clump of sporulating mosses by JoAnne Lightner. Mohan also uses natural light to advantage as it gently tips "Old Cat Tails and Young Tree Tubes" and backlights the purple/pink flush of "Green Belt Flora."

Linked to Pittsburgh's anniversary, this exhibition also continues a series of themed shows that highlight the work of regional photographers, giving them exposure to a large audience and offering visitors opportunity to see the region anew.

Other exhibitors are Gayle Bair, Ruthanne F. Bauerle, Mary Jane Bent, Gerald Hare, Amy Kathleen Lamb, Anne Medsger, Duane Rieder, Donald M. Robinson and Fiona Wilson.

As an added visual bonus, both photographers showing in the adjacent New Works Gallery, Minnesotan Beth Lehman and Californian Dorothy Gantenbein, draw their luscious imagery from the natural world (through July 19).