Though plastic sushi grass is a modern development, the idea behind it has been around for centuries. Flowers, leaves, fruits and branches have been used to line vessels in Japanese cuisine for over a millennium, according to Nancy Singleton Hachisu, a James Beard Award–winning food journalist and an expert in authentic Japanese cuisine.
The use of leaves to separate food, however, became common during the Edo period (1603–1864). “Originally, the Kanto region (around Tokyo) used sasanoha [leaves from the bamboo plant], while the Kansai region (around Kyoto) used haran.”
We have people growing kale, but I think a lot of it ends up in green smoothies, a handful of restaurants, and maybe something like animal feed (though not sure on that last one). Something like hakusai or other greens ribs with mild aroma might be a possible substitute, but it could also impact shelf life.