It's not automated. A moderator of a forum can split a post off from one thread into its own new thread.
Your short-lived leaves information would indeed be useful. We have an "Other" field under Leaves where you can type whatever you wish. We can either use that for this, or I can add another checkbox for this information. If we did the latter would "Spring ephemeral" under "Leaves" be clear enough?
The issue I see is that "Spring ephemeral" refers to all aerial parts, not just leaves. So it's more of a "habit" or "life cycle" (not sure which)