Water-Wise Cucurbits

The root systems of this family are far more extensive than most
people realize. Usually a taproot goes down several feet and then,
soil conditions permitting, thickly occupies a large area,
ultimately reaching down 5 to 8 feet. Shallow feeder roots also
extend laterally as far as or farther than the vines reach at their
greatest extent.
Dry gardeners can do several things to assist cucurbits. First, make
sure there is absolutely no competition in their root zone. This
means[i]one plant per hill, with the hills separated in all
directions a little farther than the greatest possible extent of the
variety's ultimate growth.[i] Common garden lore states that
squashes droop their leaves in midsummer heat and that this trait
cannot be avoided and does no harm. But if they've grown as
described above, on deep, open soil, capillarity and surface
moisture reserves ensure there usually will be no midday wilting,
even if there is no watering. Two plants per hill do compete and
make each other wilt.
Second, double dig and fertilize the entire lateral root zone.
Third, as much as possible, avoid walking where the vines will
ultimately reach to avoid compaction. Finally, [i]do not transplant
them.[i] This breaks the taproot and makes the plant more dependent
on lateral roots seeking moisture in the top 18 inches of soil.