Sometimes a question is all it takes...
Just now a few days ago Stephen Barstow published a short video clip of how he stratifies hundreds of perennial vegetable seeds of a mindblowing variety in such a tiny space that you wouldn't believe it. In the small frame he uses milk cartons laid down on the side where he sows around 10 different varieties in each of the cartons, totaling to around 2-300 varieties each year, making sure plants from the same family isn't too close. "It’s just a wooden frame with Enviromesh draped over to stop mainly birch seeds from entering but allowing water to pass through."
Here's the link to the blog post that contains the video and further description:
If I knew how to embed I would, sorry about that, but here's a screen shot:
The grower is Stephen Barstow, the author of the book Around the World in 80 Plants
that Maddy Harland in Paul Wheaton's Podcast 239
described as "an ethnobotanist dream traveller log". His book gets a solid 100% 5 star rating on Amazon and 10 out of 10 acorns on the permies.com book review chart.
Thanks to notoriously curious Benedicte Brun for asking him this simple question of how he does it!
Fun fact: He has aprox. 2000 varieties in his half an acre edible garden, and routinely makes a gimmick of putting hundreds of edible plants in a mixed salad. His record is over 500 different edible perennials in 1 salad, all coming from his garden.