What you do is to get
unglazed clay pots, bury them near the plants, and put water in them.
The water leaks out very slowly, because the unglazed clay is
permeable. This creates a water plume underground.
What you see here are ollas, each made from two unglazed clay pots.
These pots cost $1.03 at K-Mart,on sale. Two are
bonded together using caulk. I used caulk that is intended
for kitchen counters, figuring it would be relatively nontoxic.
One hole is filled in; the other is left open. The
ollas are buried such that the hole peeks out.
The photo illustrates:
1) on the left: a buried olla with a matching clay cover.
The cover is intended to be used as a tray to set the pot on,
but here, it is used to cover the hole. You don’t want to
breed mosquitoes and propagate West Nile virus, after all.
2) middle, lower-left: one olla with the open hole on top.
3) middle, upper-right: one olla with the occluded hole showing.
4) one of the covers laying on the ground.
5) a buried olla, with the opening showing.
6) various tomato plants.
7) soaker hose.
Some people connect the ollas to a
href="http://www.sfmga.org/olla.htm">drip irrigation system.
This is done by getting corks with holes in them, and
threading tubing from the irrigation system emitters into the corks.
The ollas help to conserve water. Perhaps more importantly,
they help keep the plants alive.