Moss thrives in shady, damp, cool areas. It also likes acidic soil, but that's not a requirement. It is an opportunist, it moves into or spreads into areas of little competition. You won't have moss in a healthy stand of grass. If the grass thins, then the moss will move in to take it's place. Does this area receive enough sun for grass? How many hours of sun does it receive when the trees are leafed out? To kill moss I use a product called Moss Out. It's a liquid iron solution that's cheap, easy to use, and harmless to you and your grass. Weed control products aren't used for moss. If you want to seed the area, you will have to have bare dirt. You don't seed over moss or other plants. Those soil pH testers don't work as well as a soil test. If you want to know for sure if your soil pH is ideal, then get a soil test (www.loganlabs.com). Liming is necessary to raise low pH. If your soil is very acidic then that will make it harder to grow healthy grass, since low pH is a sign of soil imbalance. I didn't bother testing my soil years ago. Then I got a soil test, and discovered my pH was around 5.0, which is one of the reasons why I had a sub par lawn with plenty of moss. Once I started correcting my soil, and used the appropriate shade tolerant grasses, then the moss went away.

It occurs to me to ask how vital it is that this area have grass? You could get grass to grow if you nullified the moisture and shade characteristics you describe, but even at that, you would be left with 400 square feet of lawn on the side of a hill to mow.

Maybe you should go with what nature is telling you about the area--that it is shady and moist--and plant a groundcover and/or some shrubs that would like the setting. Another idea would be to start a rock garden, or even to add a water feature (water running downhill is highly sought--it sounds like you have a natural setting for it).

Just some thoughts. Best Wishes--Carl

Moss does not have a vascular system therefore weed killer will not work. You can manually remove it with a hard rake. You will need to get grass in there growing asap to out compete the moss coming back. As stated check your ph.

"Maybe you should go with what nature is telling you about the area--that it is shady and moist--and plant a groundcover and/or some shrubs that would like the setting. Another idea would be to start a rock garden, or even to add a water feature (water running downhill is highly sought--it sounds like you have a natural setting for it).

Just some thoughts. Best Wishes--Carl"

+1 Carl!!

Hi, sorry for the delayed response.

@Carl, thanks for the ideas. I just dont know if 'decorating' that area would look nice, or even natural. The moss is on the top/flat part of the hill, and then down along the slope in a wide area.

@everyone, When home tree (this enormous 150 yr old tree) is leafed out, that portion gets shady. To rake up all of that moss, reseed and and keep up with the watering for 1-2 months in that large of an area, is going to be a chore. And if it does not work out, I am left with a hill that is half grass half hideous looking dirt. It may or may not work out because of rain water run off and/or shade(if we have one or two big storms this spring then the planting area will be destroyed. Ive seen it happen in other parts of the lawn),

Maybe I will just have to suck it up, rake and do it.

question: why would I put down moss out if I can just rake up the moss and get down to the dirt easier?

The easiest and most effective way to get rid of moss is by raking it and re-seeding, forget herbicides.

A thick stand of grass will prevent it from coming back.

Thats going to be a lot of dirt that is showing with no garuntee that I'll be able to get grass growing. I grew a small patch of grass in that area last spring. It actually came in nicely and was full. But because of runoff and shade, it is now moss.

I did lime a week ago, but that wont take effect for a long time I think.