Seedling is a Digital garden concept, used to mark articles that are published publicly for the purpose of sharing learning online, and where the author knows the article is in an early form. After receiving some care, seedlings should transition to Budding status and eventually become Evergreen, but we know from experience that not all seedlings survive.
See The value of growth maturity in a digital garden is marginal for a discussion of why notes are not marked Seedling in this Digital garden.