Imagine walking down a tree-lined street, on a glorious afternoon in the middle of spring. The male trees on the block are puffing out pollen, and you're suffering as your tear ducts and nasal passages react to the allergens that assault your body.

It doesnt have to be like that, suggests Steve Strauss, a professor of forest genetics and biotechnology at Oregon State University. In the future, city tree departments might purchase genetically modified (GM) trees that never produce pollen or fruiting bodies, just leaves. Instead, they would redirect the energy normally expended on reproduction to grow more quickly.

Genetically engineered "male-sterile" shade trees, Strauss says, "would reduce health impacts in the Southwest, in Southern California in particular (which has an especially large percentage of allergy sufferers) and not change any other characteristics of the trees.

But creating non-allergenic trees, Strauss says, will be possible only "once the technology is reliable," which may take as much as a decade or more. So far it's been difficult to get the right genes in the right places to create the desired effects. In his lab, Strauss says, "the crux of the scientific work is determining what makes trees flower at a certain time," so that flowering can be controlled or the genes cut out altogether. Energy once spent on flowering might then be focused on growth.

Non-flowering plants could also ensure the containment of genes for herbicide resistance (or other traits conferred to the organisms), counteracting the concern that transgenic trees would spread their lab-produced genetics throughout nearby wild forest. "We move trees around the landscape, out of their native range, sometimes pretty significantly," Strauss says. "This could be a tool to keep those highly bred genes from polluting the wild type."

Though it is hard to imagine a spring without allergies.