Q.Why are Pampas Grasses bare in the middle?
I have new grass all around the outside but bare in the middle. It gets plumes, but it did the same thing last year. This summer will be their 3rd year.
This can be a common growth pattern for Pampas Grass, especially in a more wet location.
Many people will dig up and divide the Pampas Grass when this occurs.
This is not easy task!
Here is a few links with more information.
https://www.gardeningknowhow.com/ornamental/foliage/pampas-grass/pruning-pampas-grass.htm
https://www.gardeningknowhow.com/ornamental/foliage/pampas-grass/growing-pampas-grass.htm