Cactus

A Cactus (plural Cacti or Cactus) is a Plant block that occurs naturally in deserts and mesas. When any entity, including players and mobs, touches a cactus, of damage is taken (damage is dealt every 0.5 second). The block can be harvested easily by either:
 * 1) mining the block underneath,
 * 2) making that block fall,
 * 3) directly by hand if the player body does not come in contact with it.

The block has three textures; one put on all vertical sides of the block, another on top, and the third on the bottom (which looks like a simpler version of logs).

Cacti will destroy any items that come into contact with them, including cacti blocks harvested above them. If a player or mob dies by cacti, it is possible that many of their dropped items will be destroyed. Therefore, traps made with cacti in order to farm resources aren't very efficient. However, this destruction can be harnessed. Cactus can be used to make garbage bins and is safer than lava since it deals less damage when touched.

Cactus can be cooked in a furnace to make cactus green dye.

Growing conditions


Cacti naturally occur in desert and mesa biomes. Cacti grow only on sand and to a maximum height of three blocks, though higher stacks can be placed by the player. Despite this growth limit, they occasionally generate naturally at a higher height if two generate on top of each other. Cacti can only be placed either on sand or on other cactus blocks, with no horizontally adjacent solid blocks. Bone meal does not work on cacti and won't speed their growth.

When the spot a cactus is placed in becomes unsuitable, such as when a solid block is placed next to them or their own sand block underneath is harvested or falls, the cactus block will uproot. This makes farming with pistons very efficient. When destroyed in either this fashion or by direct player action, the cactus block and any above it collapse into blocks that can be collected and placed again.

Cacti can be placed underwater, provided they are placed on sand, and will grow if they break the surface. Cacti placed in a one-block depth of water will grow normally. A two-block cacti stack placed at a two-block depth will grow to the three-block height. Any higher stacks at greater depths will need to be placed entirely by the player. An interesting use of this is that since cactus blocks are transparent, high stacks of them that break the surface can be used to extend sunlight deep underwater.

Cacti do not need light to grow and are non-flammable. As such, they grow well in the Nether.

Cactus, unlike other blocks can only be placed up to level 254 on the Y axis.

Farming
There are a few basic issues for cactus farming:
 * The plants need to be placed on sand, and not next to any other block. Checkerboard patterns work well.
 * When harvesting them, a nearby cactus or remaining block can destroy the drop.

This leaves a number of ways to harvest them quickly:
 * Mine out the sand underneath it, all the blocks will drop.
 * Place a block next to the base of the cactus—again, all blocks will drop. In a checkerboard pattern, you can take down two or three plants at a time this way.
 * Break the bottom block. Yet again, the whole plant will drop as items.
 * The painful way: Jump onto the cactus and mine from the top.  You and your armor will take damage, but probably survive. Works best in the free Pocket Edition.

It is also possible to make a fully automated cactus farm, which when complete, requires no further effort from the player to harvest the resources, also shown here.

Cactus defense
Due to their ability to damage entities and automatic growth, cacti can make a barrier around safe locations if a player can dedicate a few days of game time to deploy them properly. There are pros and cons to using a cactus wall, and are best placed as a secondary wall around a well lit fenced area.


 * Cacti are higher than fences and can block the arrows from skeletons. Unlike fences, however, a player cannot see beyond them.
 * Creepers and zombies may walk into a wall of cacti and injure themselves while attempting to attack a player. This can now be almost impossible because they have a path-finding AI since 12w03a.
 * Cacti grow with no supervision, and a player doesn't need to search out in the wilderness for more materials to extend the wall. However, they will grow at their own rate and cannot be sped along.
 * Cacti act as a disposal, allowing players to destroy items by throwing it into the cacti. This method of disposal is much safer than lava because it doesn't kill as fast.
 * Torches cannot be attached to cacti. Instead, torches must be set into the sand between cacti or along a separate fence.
 * Passive mobs will frequently wander into a cactus wall and die. This is more common in a vertical or horizontal setup, as they may find themselves blocked on three sides. This may make gathering their loot easier if cacti didn't destroy whatever they end up dropping.
 * It is possible to make a trench with cacti at the bottom to stop land based mobs from getting to your house.

Because they cannot be adjacent to any other solid block, a cactus wall must be built diagonally or in a zigzag pattern two blocks thick. To extend the wall, a player needs only cut down the top two blocks from a cactus and place them elsewhere. Unfortunately, some cactus items may be lost to the damaging effect of other cacti nearby.

In some rare situations mobs can get onto a single cacti block, not by path finding but when jostled by other mobs or when aggravated by the player. Since the damage likely won't kill it instantly they can then jump on to a neighboring fence or reach otherwise unexpected places (creeper trigger distance, skeleton line-of-sight etc.). Therefore in risk areas one might not want to wait for natural growth of the seed block and stack two or three cacti blocks at once.

A good defense is a large zigzag square, expanding it as you go along, only wanting the seed block. This will make a large deadly square that mobs wander into (Before improved AI).

Trivia

 * Cacti are not quite a full block wide ($7/8$ of a block), similar to chests.
 * The bottom of the Cacti block does not damage the player.
 * Cacti use the same sound files as wool when they're being broken and placed.
 * When a minecart hits a cactus block, the minecart is destroyed and dropped (the item instance of the minecart is also often destroyed).
 * Cactus can be placed next to saplings, but the cactus will break when the tree grows.
 * Placing iron bars on top of a single cactus will cause only the corners to damage.
 * It takes about 18 seconds for a player to die from cactus (without armor) if the player has full health and the hunger bar is full.
 * It will take around $5/6$ sections of the day (sun rise, midday, sun set, moon rise, midnight,moon set) to make the first section of the cacti grow in a normal area condition.
 * Endermen can move and place cacti.
 * Damage from touching a cactus is reduced by armor, but touching it also damages the armor.
 * In Minecraft Pocket Edition Lite, dropped cactus is 2D (like Flowers).
 * Signs can be placed on cacti (only on the top).
 * It is possible for cactus to generate on the sandstone in a desert temple or desert well.
 * Cactus can occasionally naturally generate at 4 blocks tall, even rarer at 5 and 6 block heights and even more rarer at 7, 8 and 9.
 * They mainly generate from one, two or three blocks.

Gallery
Kaktus Cactus Cactus Cactus 선인장 Cactus Kaktus Кактус 仙人掌