almost no mow shade grass
This fine fescue is gorgeous as an understory ground cover. Make sure you mow it twice a year because when it starts falling over it will be so thick as to block any sun and/or trap moisture and you'll get rot and grass kill. When it starts the fall over and sweeps you have about a month before you have to mow it.
The height to mow is critical. I've not found any mowers that will leave 4" of grass. A rotary gas powered mower would be ideal as the whirling of the blade actually pulls the blades of grass vertical for a clean uniform cut. Perhaps you'll be able to find one or have your mower 'adjusted, refitted' by a great 2-stroke engine repair shop. Similar to having one's Harley lowered so feet can reach the ground solidly only this is upside down; raising the bed of your mower. I'd probably mow 3X per year; once in late spring, once in late summer and once late fall. Do not allow the grass to go into winter long. 4". Don't forget fertilizing (the new organic fertilizer by Dr. Earth for lawns lasts longer...you might get away with just twice a year fertilizing, this is the best stuff!).
Make sure you grade and roll the soil before seeding. If I were you I'd do the grading and raking and rolling myself allowing for large lazy rolls versus being flat like a normal lawn. Then I'd hire a grass seeding company where you would order the seed you want, they spray it in a concoction of mulch and fertilizer which is pretty tough to recreate yourself...this is for SUCCESS. If you do the seeding yourself, you HAVE to use a mechanical spreader. If you do the fertilizing same thing use a mechanical spreader. No throwing by hand!!
Watering you will keep the surface moist (sometimes 3 or 4 times per day or more if the weather gets really warm). If you allow it to dry out at all you will be killing the germinating grass seed. Another reason to hire a grass seeding company. I would also paint circles around your trees keeping grass away from the base of trees. And shrubs.
More than likely you will be using a weed wacker/line trimmer (gas powered) and you don't want to kill your trees and shrubs by nicking the bark. Very quickly you can end up cutting the vascular system, a thin layer below the bark. Just like taking a knife to girdle a tree, a line trimmer will girdle trees, shrubs easily. A slow, imperceptible death.
Fertilize after your mowing sessions. This grass is very thick and can easily block any fertilizer from getting down to the soil. Do bag clippings or rake! Without sun you'll get thatch quite quickly but if you use that organic lawn fertilizer (Dr. Earth's is the only one I've used in this class and it comes with thatch decomposing bacteria) will help decompose any organic material that settles onto the surface of your lawn bed.
Once your new baby grass is 4" in height, you'll do your first mowing. Sharp sharp blades please! After this mowing should be your first fertilizer application. Shade plants do not do well being over fertilized. Fertilization causes more growth and being in the shade this fast growth can cause problems for the plant because it is unable to make it's own food with respect to the new growth to maintain. Plants make their own food via sunlight! I would not use fast release fertilizer high nitrogen ever on this shade, meadow grass.
In the fall you'll need your final mowing and a fall fertilizer...lower in nitrogen than phosphorus and potassium. Equal or higher percentage of Nitrogen will cause too much new growth that is susceptible to all kinds of fungus during the winter and early spring. Low Nitrogen, higher percentages of phosphorus and potassium will help the roots gain root??? Grins!
Watering at the beginning will keep your germinating seeds viable and before you can relax about your under story meadow you need to TRAIN your grasses' roots to grow deep and be drought tolerant. Once you've trained the roots, then watering will only be necessary when there hasn't been any rain and the temperatures are very high. This long grass on the forest floor also slows evaporation not only for itself but for your trees, shrubs and other under story plants. A cheapo oscillating sprinkler is the absolute best, just move it around a few times and pay attention to the amount of time you water, how deep into the soil. Very short times at first and then when training your grasses' roots very deep.
After your first mowing, when your footprints after stepping on your grasses stay visible, then your first deep watering is necessary. Make sure you water until the soil is moist down 2". Allow to dry until you see your footprints again. I'd also dig a little hole 6"x 6" so you are able to see the profile because your grass will be long at this point and beginning to fall over. Water deeply again once the soil has dried to 2". During this training period I would mow 4X maybe 6X for the season. Remember we are training the roots so they grow deep and the next season will be easy peasy using only 3X deep watering if it doesn't rain.
The second time you water, water at least 3" deep and allow to dry. If your grass is laying over, I'd mow before watering. The next time water to 4" and allow to dry. When you do your mowing, try the footprint thing. The grass blades should be thirsty enough they will stay down when you walk on them. Do not water if that soil has moisture! You can continue this until 6 - 8" deep and your grassroots are 6 -8" deep.
This fescue genetically has a deep root system that needs food that the plant makes! Remember your grass is in the shade, without a lot of sun there isn't much food for those roots. This is the biggest reason for the height of grass. Cut too much of the photosynthetic food making factories off and the entire plant is stressed. This is true of all plants, lawns.
Again, I would not leave the clippings. Mowing only 2 or 3 times a season means an awful lot of clippings that will block what little sun the live grass blades are able to get, they also cause moisture around the crowns of the roots and blades and fungus love those conditions. And then there is thatch which won't easily be decomposed and will block any rain, any fertilizer added. Don't forget to aerate! Once per year. Sounds like a lot of work but it really is not. This will make the difference between mud and this carpet of soft, fine grass you see in my post. All your work and vigilance will pay off!