You must have DARK CAVE BACKGROUND and CAVE DIRT to make CAVE COLUMN. CAVE COLUMN is in terrain category. Growing CAVE COLUMN takes 0d 00h 01m 08s. CAVE COLUMN gives experience points when broken. How many times you need to hit it? Head to the wiki for more info: <a href="https://growtopia.fandom.com/wiki/Cave_Column">cave column</a> By default you should get at least 1 seed back. Profiting with this might be questionable. Will you get enough blocks to build something? You just have to find out yourself.