Sacha wrote:
The key to growing many of these
things is to think of the conditions in which they occur naturally - olive
trees, lemon and orange trees etc. are all used to sharply draining rocky
soil with searing heat and very little water indeed.

I live in the Valencia Region, and the orange and grapefruit farmers
use enormous quantities of water. It has become a political bone of
contention because the previous Government promised to pipe water down
from the Seguro river, and the present Socialist Government has refused
to carry out the plan. Farmers who previously eked out a living growing
almonds, grapes and olives that required no artificial watering, and
the small traditional Valencia oranges that fruit in our winter, took
advantage of EU subsidies to grub them out and re-plant with more water
greedy citrus. Although well able to stand high temperatures, oranges
require water when fruiting.

Jo in hot and humid Spain