Watering Your Outdoor Cacti
Yes! they need it... Watering is the most asked question that we get at the nursery. Let me first say that every situation is different. Also, if you are having success don't listen to me.
The rules that I have always had success with are:
Water slow and deep with in ground cacti, this seems to really keep them from stressing so much and grow more evenly. This is also referred to as 'deep soaking'. Deep soak is a slow, but steady, drip from a garden hose over a two to six hour period. The size of plant determines the duration.
Watering in Pots: I water twice. First, I water several pots at a time (about a 4 foot section) enough to fill the pots. Then I go back and water again so this time the water is drawn deep and evenly into the pot and soil. I call this the "sieve effect".
Daily temps are a factor: In warmer temperatures, more watering is required. In cooler temperatures, less watering is required. See 'Seasonal Watering Tips' below for more information.
Size of plant counts: The larger and more established the plant is the less often you will have to water. It's a larger "storage tank" and can go longer between watering. For example a large Saguaro (IN WETTER THAN VEGAS CLIMATES) may never need watering where a tiny 1 gallon gold barrel could take as much as once a week watering.
Don't water newly planted cactus: If you are repotting or adding to your landscape the same rules apply, plant dry and wait to water. Watering all depends on the weather, the cooler it is the longer you wait for that first drink. You should usually wait at least a week, this gives the succulent roots time to heal before being exposed to water. Only water again when the soil is dry at the roots, each situation is different, no two are alike.
Reprinted with permission from ArizonaCactusSales.com.