An ally member and I tried to build hedges and flower beds on mine tile borders using the crafting window. Result was that the action starts and stops in the crafting window with no message in the event log. However, adding a flower and sprout to the crafting window produces the correct result in the opposite side of the crafting window, ie hedge or flower bed. I'm not sure if the bug is that the crafting window shows that flower beds/hedges are buildable or just that it won't build them.
To reproduce, activate flower/sprout, right click tile border in cave, add to crafting window, then click continue and watch the que bug out.