EA has fixed the Bug with 1.101.290 but some people still have the Issue. I recommend to only use the Mod, when you indeed still have the Bug!

Since i cannot guarantee that it works for non Season Users, i mark it as "probably only works for Seasons Only".

For whatever unknown reason, Plants revert back to Dirt Piles very often. Even EA can't seem to find the reason for that happening, so this Fix is a workaround. The Fix checks the Plants for the Planted (Dirt Pile) Object State, and if that is the case, it checks if it is in Season/Out of Season etc., if it is Inside or Outside, and what the current Quality is. If those tests together pass, it will reset the Plants/Trees back to the Blossoming State. This check happens on load and in an interval of 5 sim minutes.
Optional Addon:
For me it did not make sense that Plants/Trees Out of Season & Outside would go back to Dirt Piles as well, so instead they will stay in the Mature State. It uses the same on load & 5 sim minutes interval checks.