Can i do a radical trim of weeping willow in may?

Can I perform a radical trim of my weeping willow in May? It has overgrown the yard and blocks out the sun.

 

A bit late. Not likely to kill it, but re-growth may appear somewhat underdeveloped.

 

thanks for the reply. I was hoping to trim out all the non-vital looking stuff underneath then cut the hanging greenery up to the canopy level and leave it green on top. Some of the higher limbs would go but there would be a lot of it left as well.

 

Should be no problem. Not the same as cutting it all down to a stump or low branches. Removal of dead wood in particular will have no effect on growth of live portions.