a picture would be worth a couple million words of speculation ...

but if the leaves went from full shade.. to full sun when the sun is at its most intense levels..

most likely.. they got sunburned.. and fried themselves ... otherwise known as scorch ...

i would suspect that it has nothing to do with the roots per se ... but the plant might also benefit for some extra watering ... if you notice that the soil is drying much faster with all that sun ...

PW is pretty hard to abuse to death .. and i suspect that it will recover.. again.. w/o a pic that isnt easy ...

all you can do is watch and wait .... it has plenty of time to reflush.. with leaves that will emerge... acclimated to the new sun levels ....

good luck

ken

If the trees were cut down just recently the willow is probably getting sun burned due to the sudden change in aspect at a time when it was in leaf. While willows generally need full sun for best development leaves formed on yours while it was still in the shade will not be able to maintain themselves after a sudden radical increase in exposure to hot sun. If all other factors - such as keeping the roots moist - are kept favorable specimen should be able to produce new leaves and continue on, likely enjoy the removal of the shade.