Delano, Minn. -- Al Sterner and Jean Peterson have a hot method for weeding their 50-acre vegetable operation. They cook the weeds with a propane torch.

On warm growing days when the air is still, the pair don protective long-sleeve shirts and heavy pants. They shoulder backpacks containing small tanks of propane. Then they stalk the field, aiming flame-shooting wands at the weeds and nicking the tops of their two-week old onion or corn plants in the process. The corn and onions get a little droopy, but come back. The weeds die.

"With onions, flaming is similar to a freeze. It knocks over the tips a little bit," Peterson says, "but the plant is pretty hardy; it just sends up new growth."

When the field is large, Peterson or Sterner take a tractor and hook up a two-row weed cultivator with a propane tank and four adjustable flame-shooting wands.

Passing the torch to others

The married owners of Peterson Produce, Sterner and Peterson built their business on minimal chemical use, and say "flaming" weeds reduces their operation costs.

Last year they reduced hand-hoeing hours by 70 percent in flame-weeded plots.

Flaming is also cheaper than pesticides. Propane costs Peterson and Sterner about $10/acre, while herbicides cost about $25/acre.

Members of the Crow River Chapter of the Sustainable Farming Association, Peterson and Sterner are participating in a PRO-funded Sustainable Farming Association project, and they're sharing their expertise at field days and winter workshops.

Although flaming is not common in the vegetable industry, Sterner and Peterson hope the method will catch on fire. Weed control is broad spectrum, there is no weed resistance, and the equipment is not expensive.

Safety, however, is a major concern with flaming. Peterson and Sterner always inspect the propane tank for pits, dents or rust, and they underfill the backpack tank to avoid any chance of getting burned. They flame on calm days, and set the torch on pilot when turning at the end of the row to avoid setting grass on fire.

Full time and hard work

The couple has set up four weed treatments in onions, each replicated four times -- flame weeding with a cultivator, flame weeding by hand, chemical herbicide treatment and conventional cultivation -- and they set up control plots. With U of M researchers, they will compare the labor and economics of flaming with chemical treatments. They hope to show large commercial growers that flaming reduces pesticide costs.

"The large scale commercial grower may be able to eliminate their second or third sprayings," Peterson says. "A pass of the flame is cheaper than a pass of the herbicide. There's no doubt about that."

For Sterner and Peterson, the vegetable operation is full time and hard work. They hire high school kids to help with weeding and harvesting. They sell all of their produce at their roadside stand on busy Hwy. 12 just 40 minutes west of the Twin Cities.

"I think the challenge for us," Sterner says, "was to be able to produce enough to make our living doing this, so we wouldn't have to have other jobs."

"We've built our roadstand business on freshness and quality," Peterson adds, "and our customers really appreciate that our products are chemical-free."