Flower Pot

A flower pot is a decorative block that allows one block high flowers, saplings, mushrooms, and cacti in it. Plants that cannot be placed in a pot include any two block high plant or flower, wheat, vines, lily pads, pumpkins, melons, nether wart, sugar canes, potatoes and carrots. If the block beneath a flower pot is removed, it will break and drop itself and the plant it contained. Mobs cannot spawn on a block with a flowerpot on it, full or empty.

Flower pots can be placed on upside-down slabs and upside-down stairs. They can not be placed on normal slabs and stairs. When aiming at the side of a transparent block behind or above a crafting table the pot will not be placed on said block but on top of the crafting table instead. The same method works for furnaces and dispensers, but not for fences, cauldrons or chests. Flower pots are 3/8 block high and can be stepped on. It is not possible to walk from the top of a flower pot onto a full sized block without jumping. Despite appearing to have dirt in them, they do not require dirt to craft.

Natural Spawning
One flower pot spawns in every witch hut, containing a red mushroom. This is not the best source in the game, though, as witch huts spawn only rarely. So, it's better to make bricks and make one yourself.

Data values
Flower pot information is stored in the associated block entity. See Block Entity Format for details.

Trivia

 * The flower pot is based on a suggestion from Reddit, like Ender chests and item frames.
 * When placed in a flower pot, cacti will not harm the player or destroy items.
 * Flower pots break falling sand and gravel blocks.
 * Like cake, bed and hoppers, flower pots have a circular shape when viewed in an inventory, but has a square shape when placed.
 * Cacti in flower pots appear to grow on soil, although cacti can normally only be planted on sand.