This is Phragmite reed, a large perennial grass found in
wetlands throughout temperate and tropical regions of the world.
In the UK it's known as Norfolk reed or water reed. It is used for
thatching and here being collected by interns at
Straw Bale Studio in Oxford, MI, USA. You can find the studio
on the natural homes
map here . It must be wonderful to have your roof just growing
outside your front door.