On a Tuesday in mid-August on Hunting Park Avenue in Nicetown, Jeff Campbell, 70, is putting long, thin, flexible hoops in place for a solar greenhouse that volunteers are building. Sajir Hightower, 9, sells okra and onions picked here a few hours ago to Lois Barton, 82, who pays for her purchases with a $5 coupon from a Farmers Market Nutrition program set up for older adults.

Anyone wondering about the phrase food justice can see it in action here. And Steveanna Wynn, who heads the nonprofit that made all this possible, is so pleased that she's just about smiling her face off.

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The nonprofit is SHARE Food Program and after starting in San Diego in 1983, a branch was planted here in 1996 and has been keeping people well fed ever since. Wynn is executive director.

SHARE offers deeply discounted food in two ways: There's an online ordering service (sharefoodprogram.org) through which individuals and food pantries can submit orders monthly for just about anything - meat, poultry, fruit, canned goods, dairy, even frozen pizza and french fries.

Or, neighbors like Barton can stop by and purchase vegetables that SHARE grows on site in "high tunnels."

The tunnels are made by staking huge flexible hoops in the soil and covering them with heavy-duty plastic that retains heat. Voila: It's a passive solar greenhouse, no electricity needed.

High tunnels extend the growing season so that fall crops thrive and can be harvested into December, and frost-sensitive spring crops can be planted at least a month earlier - in March, instead of April or May.

Campbell and a dozen other volunteers constructed SHARE's two high tunnels, paid for with a grant from Pennsylvania State University.

In providing volunteer labor, they were fulfilling SHARE's one requirement: Whoever receives must also give.

Online shoppers are asked to volunteer two hours of their time a month, at the place of their choice. That could mean assisting a neighbor in need or shelving books at a library.

"Anybody regardless of income or education can buy from SHARE," Wynn says. "And everybody can give back."

Watch a video of the "high tunnel" construction at www.philly.com/sharegreenhouse.EndText

Contact staff writer Dianna Marder at 215-854-4211 or dmarder@phillynews.com. Read her recent work at http://go.philly.com/diannamarder and follow her on twitter, @marderd.