Farming cactus: The saguaro cactus, native to south-western United States
Prickly pear: Opuntia, one of the most common type of cacti found in North America. In the Kharidian Desert, some prickly Pear cacti may act as a water source; they are designated "Kharidian cactus (Healthy)". Water is added to an empty or partially empty waterskin or vessel in the player's inventory, when a knife is used on a healthy cactus. There is a chance of failure, however, so a player may have to cut more than 1 cactus to bring a waterskin from "Waterskin (1)" to "Waterskin (2)". Success or failure is indicated by a message, as well as the presence or absence of a gurgling water sound. Cutting a cactus successfully grants 10 Woodcutting experience, whilst failing to cut one grants 1 experience. There is currently no way to increase the chance of success.
In real life, the alkaloids in a cactus can make you vomit, which means you'd end up losing a lot of water, and could fall into full dehydration very quickly. It is not recommended for survival in real deserts.
A cactus can also be grown with the Farming skill using a cactus seed at the cactus patch in Al Kharid with 55 farming. The seed does not need to be used in a plant pot, but can be planted directly into the patch. The patch does not need watering, and, as of 21 August 2012, can be watched over for 6 Cadava berries. To grow another, use a spade on the patch to clear it first.
Once the cactus is fully grown it will live forever and will not need to be taken care of. It will also regularly provide 3 cactus spines, which you can harvest with your bare hands.
When you cut a cactus for water it appears that you are using a Bronze Throwing knife, instead of a regular knife. This is because, at the time the animation was made, there was no animation for the regular knife. There are now animations for Fletching with a regular knife, but the animation of cutting a cactus has yet to be updated.
