Brian wrote:


The foliage of all plants directs water flow to where it is most needed.

Even if this were true, the total quantity of water which reaches the
place where it is most needed is surely reduced by foliage. So in
dry weather, or when the amount of water available is otherwise
limited, there may still be good reason to deliver water directly to
where it is most needed in the soil, rather than delivering it as
run-off from the foliage.

Ken