I have heard that you should not plant pampas grass next to a lawn area because it will go to seed and these seeds will start new plants in your lawn.
Cortaderia selloana, or Pampas Grass is hardy to zone 5. In looking at one map of "potential planting area", I noticed that it did not include Colorado. If I planted one, I would consider it to be an annual until the plant proved otherwise. There is another ornamentell grass that has the same leaf, but the bloom scape is not as "poofy". That plant is known as Hardy Pampas Grass, the botanical name is Erianthus ravennae, and it is hardy to zone 4.
I've found that Pampas Grass does not seed readily. Clumps of this grass have been in a family member's lawn for 35 years in a Georgia coastal town. They have never had volunteers spring up. The clumps will become quite large with age.
The Miscanthus family is a different story. It is not known as Pampas Grass, but can become invasive if blooms are allowed to mature. It does resenble Pampas Grass somewhat...but clearly different in both heigth, width, color and bloom.
The grass is out of control, should I trim it back now? Do not think I can wait until spring.
Pampas grass foliage acts as mulch during cold weather, I usually recommend cutting it back in spring. But, if you can't stand looking at it this winter, go ahead and cut it back now. This link takes you to several articles on pampas grass: http://www.google.com/cse?cx=012078378210706707791%3Af1h5n_k1r5e&ie=UTF-8&q=Pampas+Grass&oq=&gs_l=#gsc.tab=0&gsc.q=Pampas%20Grass&gsc.page=1
Could it be that I need a male plant with the female? Four years ago, I bought 2 plants with plumes and they have not plumed yet. Very few blogs specify this reason. They all point to other reasons.
This article should help: https://www.gardeningknowhow.com/ornamental/foliage/ornamental-grass/no-plumes-on-ornamental-grass.htm
Does pampas grass have seeds that can spread to green lawn areas?
In some areas, this plant is known to be invasive as it does self-seed. That said, in lawn areas that are continually mown and kept up, this is rarely an issue, though this plant does require at least 10 feet by 10 feet of space to spread into at maturity. If the size and spread of pampas grass is a concern, however, there is a miniature variety available called C. selloana 'Pumila.' Here is more information on growing pampas grass: https://www.gardeningknowhow.com/ornamental/foliage/pampas-grass/growing-pampas-grass.htm
How and when do I cut my pampas grass back?
You can cut it back in spring to about 2-3 feet, but be careful as the foliage is rather sharp. You can also choose to burn it down to the ground (or green growth). If you choose burning, however, make sure it's not near any structures and keep a close eye on it.
I bought some pampas grass a couple of years ago. It gets plenty of sun in Florida and is over 6 feet for almost two years but no plumes.
This article should give you some ideas: https://www.gardeningknowhow.com/ornamental/foliage/ornamental-grass/no-plumes-on-ornamental-grass.htm
Plant in East Tennessee. No green on any of my pampas plants.
1) Are they dead?
2) Do I need to prune them down?
3) Must I always need to prune them down? (I love the plumes).
Winter was very hard in most parts of the country, and it may have damaged your plant. There's a possibility that you've lost it. Since no green is showing, go ahead and cut it back to the ground; you could give it some diluted fertilizer too. You should cut it back every year, which will promote more growth from the plumes. This article tells more: https://www.gardeningknowhow.com/ornamental/foliage/pampas-grass/growing-pampas-grass.htm