salix integro hakuro nishiki

a young plant, with plenty of rain water regularly (which we understand it needs being a willow) and now some of the young leaves have started to turn brown - why is this please?

Could be wind damage if your weather has been like ours!

I have one and agree with 'Spritzhenry'. Though I would add that 'windburn' can occur either through dehydration or the air temperature being too cold. You need to have noticed its timing to understand which.