WASHINGTON — Last month, Bernie Karl flew down to Washington, D.C., and installed a hydroponic grow tower in Sen. Lisa Murkowski's office. Next, he wants to hit every public school in Alaska.

Karl, who owns Chena Hot Springs northeast of Fairbanks, has a mission: He wants to teach kids how to feed their families using cheap, easily obtained materials.

Karl's daughter has a tower at her house — hers grows strawberries and cherry tomatoes, he said. In Murkowski's office, the tower grows only lettuce — enough to feed a family of six.

And for a few weeks now, the senator's staffers have been picking their own salad greens off the tower of orange Home Depot buckets in the corner of her office lobby in the Hart Senate Office Building.

First harvest from our home-grown Senate office lettuce grow tower. This is just one week of growth! A post shared by Senator Lisa Murkowski (@senlisamurkowski) on Jun 19, 2017 at 1:31pm PDT

Karl is well known to Murkowski as well as to other political bigwigs in Alaska. Murkowski, Sen. Dan Sullivan and Gov. Bill Walker routinely show up at his renewable-energy fair each August.

So it's not entirely surprising to see the tower appear in Murkowski's office, after he touted its earliest iteration at last summer's Chena Hot Springs energy fair.

"Our goal is to get one in every school in Alaska and every school in America by the end of next year — to teach third- and fourth-graders that everyone can be responsible for growing their own food," Karl said in an interview.

More than 98,000 public schools operated in the United States in the 2013-14 school year, according to the National Center for Education Statistics. More than 67,000 of them were elementary schools.

"The problem is that things are so expensive. But they don't need to be. So we decided that we would come up with something that you could go to any Home Depot and buy," Karl said.

The tower in Murkowski's office is the 3.0 version of Karl's efforts, along with others at his employee-owned Chena Hot Springs Resort, where they grow food for the staff and guests.

That tower is getting its own upgrades. On June 27, Murkowski's husband, Verne Martell, arrived in her office with a wax plumbing ring and set about tweaking a previous fix. Martell was working on quieting the sound of running water that plagued the two employees who sit at desks in the lobby, greeting visitors and answering phones.

Karl said Friday he had just sent an extra light to Martell, an upgrade for a side of the tower that wasn't growing as well as the rest.

Karl is a boisterous man — the kind of guy who has big ideas and even bigger plans. Currently, he's hoping to get a meeting with the top brass at Home Depot — he said Murkowski had kindly put in a call for him.

He's hoping to convince them to offer Saturday classes on building the tower at stores nationwide. And he wants the company to sponsor "one for every school in America."

Karl is in the process of patenting his invention — called "Lettuce Grow for Free" — but he doesn't plan to make money off it. He wants to give the plans away. And he encourages others to improve upon them.

"We're building a fourth prototype right now … that uses a little less material, gets it down a few more dollars."

Karl also hopes that school programs run by Future Farmers of America and 4-H will start programs in schools.

"I want them to help replant the world," he said of the youth agricultural organizations.

This fall, an elementary school in Fort Yukon will get Alaska's first school-based grow tower, Karl said. They were the first to ask for one, he said.

See the plans here: The Chena Grow Tower Project