Cactus generates naturally on sand surfaces in desert and badlands biomes, growing in single-block columns up to three blocks tall. The plant requires sand directly beneath and no solid block in any of its four horizontal neighbours — placing a stone or dirt block adjacent will instantly snap the spike off, dropping the segment as an item. This dual constraint makes spike farms easy to design: arrange the columns on sand with a piston above, run a redstone clock, and watch grown segments break automatically when blocked.

The touch-damage property is the plant's most distinctive trait: any entity (player, mob, dropped item) that comes into contact takes half a heart of damage every half second. Mob farms exploit this for passive killing chambers — pipe enemies into a thorny enclosure and let it work. The smelting recipe converts one segment into one green dye, the only renewable green-dye source in vanilla. The plant cannot be placed adjacent to another cactus block, so dense farms require staggered alternating columns to fit the placement rules.