Janna Traver, the executive chef for KU Dining Services, left, and Joe Pruitt, an executive sous chef, discuss and give a tour of the expanded rooftop herb and vegetable garden at the Kansas Union. Ingredients are used in the Market food court and for special dinners.

Focus groups have shown Kansas University students eating food on campus often prefer it to come from a local source, Janna Traver says. Well, it doesn’t get much more local than this.

Some of the herbs used to season foods served at the Kansas Union have to travel only a few flights of stairs from where they’re grown, thanks to a rooftop garden that KU Dining Services staffers have been tending for about four years now. Workers this week completed the biggest expansion for the garden since it began, made possible by some new space on the Union’s sixth floor provided by the University Women’s Club. They expect its output of herbs and tomatoes to roughly double during this growing season.

Traver, the executive chef for KU Dining Services, said students in focus groups say they’d like their food to come from somewhere nearby. So she enjoys the opportunity to tell students when that’s the case.

“I can say, ‘Your tomato bisque with basil is made with basil from the rooftop,’ ” Traver said.

The garden began about four years ago with four whiskey barrels filled with various herbs. As it’s expanded gradually through the years, it’s provided herbs and tomatoes for the Impromptu Café in the Kansas Union and various events catered by Dining Services, as well as herbs for salad bars in the Union and in Wescoe Hall.

But now that it’s expanded at a cost of about $600 to fill seven barrels, 14 irrigating earth boxes, 22 five-gallon buckets and three pots, workers hope for it to produce 100 pounds of herbs and tomatoes this year. Plans are for it to begin providing herbs for the residence-hall dining areas on campus, Traver said, cutting down on costs and reducing energy usage.

After workers planted 30 parsley and 24 basil plants Wednesday, Traver said, the garden should be ready to supply those two herbs in force.

“I should be able to do enough pesto to feed everyone on campus,” Traver said, “for at least a few meals.”

For this growing season, which should run from now till about November, the garden also contains 19 tomato plants of different varieties, plus several specialty herbs, including lavender, lemongrass and bright purple chive blossoms. (Those blossoms will top the salads eaten by this year’s KU honorary degree recipients at a dinner during the coming commencement weekend, Traver said.) For watering, workers use water collected by rain barrels when possible.

Workers spent all day Wednesday planting this year’s garden. Now that planting is done, it will require about an hour per day of care by Dining Services staff, said Joe Pruitt, an executive sous chef for catering operations.

That’s well worth it, he said, to know that if he ever needs, say, 5 ounces of basil leaves, he can run upstairs and snip them right off.