A Cactus (plural Cacti) is a block that spawns naturally in Desert biomes and Mesa biomes. Cacti can rarely be found on clay that is found outside a body of water. When any entity - including the Player - touches a cactus, half a heart will be lost, unless they touch the bottom of the cactus. Cacti are not flammable, so they do not catch on fire when near to or touching lava or fire. Cacti can be placed on Sand, Red Sand, and other cacti as long as there are no blocks directly adjacent to it. Cactus growth and spawning are not dependent on water. However, they can be placed beside a source of Water. Wandering Traders will sell cacti in exchange for Emeralds.
There are two good options for farming cacti: automatic farms and manual farms. Automatic farms can involve pistons and redstone to push the blocks which forces their gravity-affected nature to come into play. The other option for cactus farming is to simply place a block above and beside a single block of cactus, so whenever the cactus attempts to grow, the block will be destroyed because of the cactus's inability to be adjacent to other blocks. Another good way to make a farm is to put water around a cactus and a room under the cactus in order to catch items.
Cacti will destroy any item that comes into contact with it, including harvested cacti blocks. If a player dies by cacti, it is likely that many of their dropped items will be destroyed. Therefore, making traps with cacti in order to farm resources can be less efficient. Cacti can be cooked in a furnace to make cactus green dye.
Cacti can be used to protect one's house from monsters by: first placing two to three-block-high cacti, next put a netherrack block on the ground next to the cactus, and finally light the netherrack on fire. This is a common and simple wall which is good against all mobs. Another form of cactus defense is to surround one's home with cacti in a wall with each cactus diagonal from the next one. This is a very efficient and easier way since it does not require traveling to the Nether or anything that might be difficult to obtain. Players can also place cacti in flower pots; this way they will not hurt a player, and players will not need to worry about them being next to a wall.
- When a Minecart hits a cactus block, the minecart is destroyed and dropped.
- Cacti can be placed next to Saplings. However, the cactus will break when the tree grows.
- In the Beta version of Minecraft, cacti were slightly larger when dropped.
- One player took a snapshot of a 9-block tall cactus in his world.
- Spiders can climb over cacti, but they are hurt in the process.
- Cacti are the only plants that are full blocks also.
- The tops of cacti will also deal damage despite the lack of spikes.
- Whenever an Item or block drops onto a cactus, it will disappear which makes this a good trash disposal instead of dangerous, burning lava.
- Cacti were added in the 1.0.6 update, and players would take three and a half hearts of damage while breaking the cactus. In Minecraft Alpha 1.0.7 update, breaking a cactus would only deal half a heart of damage to a player. This was changed in the Minecraft 1.0.11 update when breaking a cactus would deal no damage to a player.
- Cacti can naturally generate up to 3 blocks high, but there is a rare chance that it will generate higher than that.
- Before the Nether Reactor Core was removed from Minecraft: Pocket Edition, one of the items spawned in the structure included cacti, although it was obtainable at this time.
- The cactus is slightly thinner than most blocks.
- The bottom of a cactus looks like birch wood, and it does not deal any damage.
- Cacti can be planted directly in water as long as the second or third block (the usual height of a cactus) will be above water.
- In older versions, the texture of the cactus, when in the player's inventory, has its side textures wrapped around the entire block.
- Endermen can hold and replant cacti. Although this instance is very rare, as when they get hurt by one, they will immediately teleport away.