If plants are wilting under the hot sun, your best save is to provide a bit of shade. Shade is also a good idea, in hot climates, for newly planted seedlings – especially those that prefer the cooler side of life like saladings or brassicas, which you may be planting out now for autumn eating.
The easiest way to cultivate shade is to plant amongst taller/ older crops, using them as nature intended – to nurture the young. In their absence, rustle up a bit of shade cloth – draped over hoops or tied to stakes.
When plants wilt
A daytime wilt/ night time recover is a clever water conservation mechanism, not necessarily indicating dry soil. The pores on the leaves (stomata) responsible for water out/ CO2 in shut down when water out is faster than water in. It’s not ideal, especially when fruits are developing. Instead of steady growth, we get stop-grow, stop-grow. What we want is grow-grow-grow!
Check your soil by pushing your finger to feel for moisture. If the wilt is from drying out then a slow hose at the base of the plant is the way to go. Shade cloth will help greatly too.
If you erect a shade cloth rescue, leave the sides open for airflow and morning/ evening sun. The cooler air beneath the shadecloth slows the driving force for transpiration, making the water you put in your soil go that bit further and preventing daytime wilts.
