Modern garden varieties of pampas grass found in nurseries are generally non-invasive. Their flowers are described as ‘sterile’, and therefore unable to produce seed. What that really means is that they are exclusively female, and unable to produce seed without male pollinators. However, they have the potential to be pollinated by naturalized pampas grass, and sow a few hybrid seed.
Of course, if naturalized pampas grass (Cortaderia jubata) are already in the area, a few tame dwarf pampas grass, Cortaderia selloana ‘Pumila’ will not make much of a difference anyway. They have the same elegantly cascading foliage and boldly fluffy flowers in the middle of summer, but on a smaller scale. The long and narrow leaves might stay less than five feet tall. The white flowers might stay below eight feet tall. Unfortunately, the leaves can easily cause nasty paper cuts!