Hello Tim,

Unfortunately, you are not going to like my answer… A lot of gardening issues are resolved by using “the right plant in the right place.” In your case, the vinca (myrtle) and hostas were probably the right plant for that place.

There is no cool season grass variety that will thrive (or even tolerate) dense shade. All grass varieties need SOME sun to grow – even shade tolerant varieties. For dense shade grasses, they still require 2-4 hours of full sun or 5-6 hours of dappled shade each day. If your problem area gets less sun than that, you may want to consider opening up the tree canopy or replanting shade loving ground cover instead of grass. Here are more considerations when growing grass in the shade: https://extension.umd.edu/resource/growing-grass-shade

If you are intent on attempting to establish grass in the area, your first step should be to have an MSU soil test performed. You will want to understand pH and nutrient needs to give grass plants the best chance at survival. https://homesoiltest.msu.edu/get-started

As far as varieties are concerned, fine and tall fescues are the most shade tolerant grass varieties, but they still require 2-4 hours of direct sun a day. I don’t understand the recommendation of perennial ryes, because they are “shade tolerant” which means they perform just a little less poorly in partial shade than Kentucky bluegrass does. If you are not getting 2-4 hours of sun exposure, you will experience an increase in shade tolerant weeds and moss as the grass plants decline. If you wish to attempt fescue overseeding, try to determine when your dense shade area experiences the most sun (early in the season before trees leaf out, mid summer when the sun is farthest north, etc.) and attempt to seed then. Some people that try to establish grass in dense shade are committed to overseeding multiple times per year (spring and fall), every year, to constantly replace the declining grass plants.

Ultimately for dense shade I would recommend going back to the shade loving plants. Right Plant Right Place…