Q.What happens to pampas grass if it’s not cut back?
What happens to pampas grass if it’s not cut back? Will the brown turn green and start growing, which means it will grow taller?
It is recommended to prune pampas grass each year to the ground in late winter or early spring. The brown stuff is dead material and will not turn green nor will it grow, which might give your grasses a more ratty appearance. I also think that if the grasses aren't cut back every year it will be that much more difficult to cut them back when and if you decide to do so.
For more information on the care of pampas grass, please visit the following article:
https://www.gardeningknowhow.com/ornamental/foliage/pampas-grass/growing-pampas-grass.htm