18 is not the maximum limit of Anima grass possible. Growing 1 anima grass should only take around 3-4 hours of meditating near the tree a day. Previously, a major update added a new Pen system, animal sterilization, new floor type, egg box, and much more. According to the official RimWorld patch notes, the latest update added variety of improvements for the base game and both expansions.
Yet another RimWorld update is now available to download on PC (Steam). The corner I'd selected took a few presses. So that one got chopped down, and I spawned a bunch in using dev mode. I put some scattered walls up in an attempt to force it into a corner, and it regrew within range of my front door walls. I tried doing that when a merchant's alphabeaver nommed the tree.
