WAPATO - Workers move quickly up and down the rows, stretching twine between stakes here in an Imperial's Garden tomato field on a recent sunny morning. The twine plays out from a spool in a small box carried on the hips of workers. They use a short stick to guide the twine around each stake and on to the next.

The longtime Valley vegetable grower is experimenting with trellising the tomatoes as part of a contract to supply larger volumes to retail giant Wal-Mart. It's the first large-scale use of trellising to produce tomatoes in the Yakima Valley, said Manuel Imperial, who handles sales for the family-owned business, which has been growing produce for 28 years.

"This is a promising deal. There is a potential for it to be a big success for us," said Imperial, whose family farms more than 1,000 acres, one of several large vegetable growers in the Yakima Valley.

Adding more tomatoes to the list of produce Imperial's already markets to Wal-Mart is another sign of a growing trend: food retailers expanding their offerings from local growers.

It's not unusual, for example, to see groceries tout their local sources with signs that identify the farmer who supplies the goods.

"It's a huge benefit," the 44-year-old Imperial said of the buy-direct movement. "It is supporting us and it is good for the local people to know where their produce is coming from."

Local sourcing is nothing new for Wray's Market Fresh IGA, a privately owned Yakima grocer with three stores in Yakima. President Chris Brown said the company recently filmed a television commercial promoting its locally grown produce offerings.

Wray's obtains about half of its produce during the summer from local growers. Just last year, the markets began stocking locally grown Roma tomatoes.

Meanwhile, Wal-Mart says it has boosted sourcing from local growers to 7 percent from 4 percent over the last three years. The company defines the locally grown market as the entire state.

Wal-Mart maintains a buying office in Yakima headed by Rich Gonzales, senior director of global food sourcing. He says there is a lot of face-to-face communication with growers.

"What we're trying to do is (figure out) how we can match the growers and what they're doing here to what our customers want," Gonzales said.

As part of the contract to supply Wal-Mart, Imperial's Garden has tripled its tomato acreage to 60 acres this year, and could expand dramatically based on this year's experience.

A majority of the tomatoes will find their way to the Wal-Mart distribution center in Grandview and out to stores in the region. The remainder will go to Imperial's other retail customers and to its own stand on Lateral A, just south of West Wapato Road.

Sharon Heer, sales manager for Rasmussen Marketing of Yakima, said the agreement is a good opportunity to showcase Valley tomatoes. Imperial's is one of her many clients in the Yakima Valley and statewide, and she handles sales of Imperial's produce to Safeway and Fred Meyer.

Heer, too, has seen the growth in direct produce purchasing by major retailers and calls Wal-Mart one of the best to work with. Wal-Mart's commitment has prompted other chains to source locally, she said.

"I'm the Wal-Mart cheerleader. I have a 20-year relationship with them," Heer said. "Wal-Mart is a real champion of the small farmer. They are probably easier to deal with and more consistent than some of their competitors."

Wal-Mart is not, as some might suggest, a low-price buyer, Heer said.

"They are my highest-paying customer. I have been taking that check to the bank for 20 years."

The Wal-Mart agreement to source tomatoes from Imperial's was developed through produce broker and transportation provider C.H. Robinson of Eden Prairie, Minn.

Imperial said Robinson flew him to Arkansas to see how trellised tomatoes grow. The firm supplied the materials, while Imperial's is responsible for the plants and crews that must keep the vines on the twine and off the ground.

The project is adding to his labor costs, which approach $3,000 per acre from seedling to harvest, but Imperial anticipates those costs will be offset by better quality and higher volume. The goal is to improve quality by keeping tomatoes off the ground, where the fruit is susceptible to damage and blemishes.

"We are hoping they ripen better than on the ground and the produce will be better," he said.

Imperial's expects to ship up to 4,000 boxes of tomatoes weekly to supply Wal-Mart stores. The farm grows three types: full size, Roma and grape tomatoes. The boxes range from 11 pounds for grape tomatoes to 25 pounds for full-sized fruit.

Imperial said he is looking forward to harvest, which will start in less than two weeks.

"We are pretty excited about it. It's a new thing and we hope it will work out," he said.

Editor's note: This story was updated to correct the percent of Wal-Mart's purchases from local growers.