That’s a very nice run! How many chickens do you have in it?I don't know where you live, I live in south central Texas and winters here are not too bad, every now and then we have freezing temperatures but must of the time it is warm. I am new with chickens (started last April) I have a big run that used to have grass but now it is all dirt so I decided to plant some rye grass seeds outside the run for my girls to eat in the winter. I was successful and it is growing very nicely. You can look at it to the right of the picture. I don't free range my hens all the time because we have lots of hawks in this area, however when I can supervise them they go out and happily devour the grass
I would think that if my 9 hens were freeranging all the time, maybe the grass wouldn't have grown so much but since they free range 3 or 4 hours a day, there is plenty of time for the grass to grow all over.