I pruned it in March. It came back up great. It is now turning yellow and dying. I fertilized it with Miracle grow liquid. Not a strong mixture. Should I cut it back again or try more fertilizer?
Did the grass receive heavy watering or rainfall in the recent weeks?
Does the grass pull out from the crown easily?
It's possible your plants are suffering from crown rot.
You mention a light fertilizer, which should have been applied in the spring. I would not fertilize again.
Allow the plant to dry out and see if it can recover.
https://www.gardeningknowhow.com/plant-problems/disease/crown-rot-disease.htm
Can I plant Karl Foerster grass in the ground, leaving the pot intact except for the bottom? I want to keep the grass contained in nice clumps that will stand upright. Is there a way to keep them from spreading haphazardly?
Karl Foerster feather reed grass has an upright growing pattern, and this cultivator is not invasive.
It will not spread with additional seedlings.
I would not plant using an open bottom pot for these reasons.
I live in zone 7. Can I plant Feather Reed grasses this fall before any frost? I need to know if I can plant the grasses now, early September, or would it be best to wait until spring?
It would be best to start new ornamental grass plants in the spring. Most can be slow to become established and grow.
I live in Fargo, ND. Wondering if I should cut back reed grass before winter. We are in Zone 3 or 4.
There is debate on when to prune your grasses.
I personally leave them for winter and trim them back in the early spring.
Here is a link with more information.
I planted a Feather Reed Grass four seasons ago and it has done wonderful with full heads. I normally cut it back to three inches in the late Fall, but this year I let it stand and cut it back in March. The grass is full and healthy looking BUT I have very sparse seed plumes...one on one plant, four on another and none on one. This is first time I have experienced this problem.
Lack of seed heads can be from not enough sun, excess nitrogen or that your grass needs to be divided.
My Feather Reed Grass (five plants) failed to develop seed plumes this year (two on one, one on another, none on one,etc.). What possibly caused this problem?
The most likely reason for lack of plumes is not enough sunlight.
They were small when planted last spring in full sun and have not grown much. This is in our southern Arizona soil and are irrigated.
If the grasses are in a sprinkler system area, and getting more than the once a week watering, that could be a problem. It also doesn't like heavy mulch. We would suggest that you trim down the grasses to about 6", if they are now dormant for winter. This will take some stress off the plant, so it is not trying to get water up to higher portions of the plant. Then, only water them once a week, and not that if there has been regular rain. Let the water dribble into the plant area from a hose, and don't water them from an overhead sprinkler system if you can avoid it.
https://www.gardeningknowhow.com/ornamental/foliage/stipa-grass/stipa-mexican-feather-grass-care.htm