As Boutard mentions in the video, he obtains his seeds from The Kusa Seed Research Foundation, a nonprofit “think tank” dedicated to preserving ancient grains through research and education, and by making their seed stocks available to the public via their online seed catalogue.
There has been a renewed interest in these ancient wheat varieties because of both their high nutritional value and distinctive flavor. For example, according to the Kusa Foundation, the artisan breads of the European renaissance came from the Spring Spelt grains, the same variety that is shown in the video. The wheat grows well even in suboptimal soils, those low in organic matter and nitrogen.
Grünkern, the green spelt is harvested in late July and kiln-dried (often smoked over beech or oak woods), that has an obvious smoky flavor, but is also sweet. When cereal grains (grasses whose grains are edible) are harvested before they ripen, the sugars remain present because they have not yet transformed into carbohydrates that will occur during the ripening stage.
Another example of a similar process, Frikeh (watch this related video: Frikeh, Freekeh, Fereek: Green Wheat Wonder), is made from green winter wheat that’s harvested and immediately roasted by flame in the field. Many traditional middle eastern recipes include this key ingredient. Check out this recipe that’s part of the Frikeh story: Frikeh Summer Salad