Subway operator Tokyo Metro Co. is bringing its ideology of "safe and secure" to an unlikely place -- farming.

Under the name "Tokyo Salad," the company is growing lettuce, assorted salad greens, and even herbs at a facility approximately a seven-minute walk from Nishi-kasai Station on the Tokyo Metro Tozai Line. The cultivation warehouse Metro vegetable center is located under the elevated train tracks of the line.

The airtight space is held to strict hygienic conditions, and neither fertilizer nor soil is used, with the seven rows of plants instead grown hydroponically. Frill lettuce, basil, along with rare finds such as Lollo Rosso (red coral lettuce) and red kale are found among the 11 varieties regularly grown, with roughly 400 plants reportedly growing on a given day.

The cultivation is completely man-made and mechanized. Seeds are placed on a sponge with tweezers, and the young seedling is raised until the leaves spread out, at which time it is moved to a more spacious area. LEDs shed light on the plants for 16 hours a day and the liquid nutrients are cycled through the system 24/7. It takes roughly three to five weeks for a plant to reach maturity, and there is barely any loss.

The strict hygienic conditions inside of the Tokyo Metro Co.'s cultivation center in Tokyo's Edogawa Ward. (Mainichi)

The leaves are not bitter or astringent, and the leaves are soft all the way to the exterior of the plant. They can be preserved for a long period of time, and because no chemical fertilizers were used to grow them and they never touched soil, the entire plant can be eaten without being washed.

So-called plant factories like this are the focus of efforts by the Ministry of Agriculture, Forestry and Fisheries to expand safe provision of products like vegetables, high productivity and job creation. According to the ministry, the number of cultivators using artificial lights has tripled from 2011 to 197 locations as of February 2017.

Tokyo Metro entered the market to make use of idle land as a new business venture, and built the cultivation facilities in unused warehouses. The operation is a joint project with group company Metro Development Co., which began sales of the lettuce and other products in April 2015.

The element of surprise and the mismatch between subways and vegetables have stirred up quite a reaction. Last spring, a lunch course featuring the products was introduced at The Strings by Intercontinental Tokyo hotel. Even the dessert included ingredients from Tokyo Salad, and because of an overwhelming positive response, the hotel introduced a dinner course this summer as well.

"Dishes where a lot of attention is paid to a single ingredient are very popular," says 47-year-old hotel food and beverage manager Tetsuya Tanigawa. "The ideology and the story behind the product is the deciding factor."

Tokyo Metro overseer Remi Takahara, 33, continued to visit the vegetable plant for the six months she was visiting potential business partners that would use Tokyo Salad vegetables since the factory operation began. "I never thought that I would be growing vegetables when I joined a railway company," she said, reflecting on the trial and error process that led to the subway operator's greens' cultivation.