Well - not to start an argument, the people who responded to my comment have
plenty of experience between them, but I have a few years of experience too.
IMHO high heat, low water, and low humidity are a _bad_ combination for Sarrs.
With good humidity and water, high temps are almost irrelevant. For example,
those Aussy Sarrs. in 40C heat are standing in water 10-15 cm (4-6 inches)
deep. Standing in 6in. of water you might find that the micro climate is very
humid. Putting aside issues of micro-climate, take 40C heat, very low humidity
and take them out of standing water and I would be surprised if they lived
three days.
While good growers can adapt their plants to their own conditions, these
plants are largely limited naturally to areas that are wet and humid
year round. With a hot, low-humidity day the plant is going to loose a
lot of water through transpiration; probably more so than plants not
originating in wet, humid conditions. If it looses excess water, or
can't take up enough to replace the loss, it will wilt. Rubra seems
more susceptable than others. If the roots were healthy but too little
water was available, wilt seems likely to me.
Humbly, Tom in Fl