Replacing lawn in deep shade area

Asked April 28, 2020, 2:15 PM EDT

Hello, I have a 10-foot wide x 70 foot long strip of lawn between 2-story house and 5-foot wood picket fence which gets little sun. The sun & shade grass mix originally planted has been totally overgrown by moss. I am looking for suggestions on how to eradicate what is there, what very shade tolerant grass to replant (if there are any), and how best to transition from it to the existing sun/shade mix in front of the house. (Note-the mix in front of the house has significant moss through it, but at a level which I think could be salvaged with more frequent thatching or.... I'm not sure if that front area (still quite shaded, but not as much as the side yard) is just getting too much water plus shade or if it really does need to be totally replaced, as well. Since this front area is over 1000 sq. ft., and I already expect to have to replace the 700 sq. ft. on the side of the house, I would like to try to salvage the front yard rather than replacing the lot if that is feasible. Martin Yedinak

Washington County Oregon

1 Response

Hello, The side yard sounds like a spot for a shade tolerant ground cover or other shade tolerant perennials. It is very difficult to keep a stand of grass when it gets little sun. The most shade tolerant grass is Rough bluegrass (Poa trivialis), but in these conditions, I don't think Rough bluegrass will compete well with the moss. To eradicate what is there, you need to spray glyphosate (Roundup). It will kill any plant that it touches so be careful not to spray desirable plants and keep the pressure of your sprayer down to reduce drift. If you want a non-chemical method, simple cover the area with plastic for a couple weeks. Once the grass and moss are dead, rent a de-thatcher and de-thatch in several directions and rake up all the debris. The de-thatcher should be set to barely scarify the surface of the soil. Keep de-thatching until you can see the soil and the new seed will have good soil contact. You don't need to remove all the debris, but enough so the seed rests on the soil. As far as the front yard goes, use the same de-thatcher set a higher setting (it should not touch the soil) to remove the moss. Go over your lawn 2 - 4 times in different directions until most of the moss is removed. After de-thatching, rake up the debris and apply Lilly Miller Moss-Out using a hose end sprayer. This product has iron so avoid spraying sidewalks as it will stain. It will turn the moss black. After applying the Moss-Out, fertilize your lawn using 2 lbs. of nitrogen per 1,000 sq. ft. with a slow release fertilizer. Do not use weed & feed as it has an herbicide in it that you don't need. Apply something with 50% slow release nitrogen if you can find it. Here is an example: GVT 20-5-5 3fe Slow Release Lawn Fertilizer (https://gvt.net/product/gvt-20-5-5-3fe-slow-release-lawn-fertilizer). Scott's Turf Builder Lawn Food is another option but it only has about 28% slow release. With 72% quick release, I would only apply 1 lb. of nitrogen and then make a second application 4 weeks later. To figure out how much fertilizer you need to apply to get 2 lbs. of nitrogen, divide 2 by the nitrogen percentage expressed in decimal form. So for example, if you are using the 20-5-5 fertilizer product shown above, it is 20% nitrogen (the first number). Therefore, to apply 2 lbs. of nitrogen per 1,000 sq. ft. divide 2 by 0.20 which equals 10 lbs. of fertilizer per 1,000 sq. ft. To keep moss out, you will need to fertilize fairly often (about 4x per year - mid to late May, early July, end of September, and mid-November applying 1 lb. of fertilizer per application), mow regularly, and water sparingly and infrequently (enough to keep the grass green). If you de-thatch, you should apply 2 lbs. of nitrogen afterwards to help your lawn recover more quickly. The other applications should be 1 lb. of nitrogen per 1,000 sq. ft. Organic fertilizers work nicely in the July and September applications. Use a different fertilizer for the other applications. Good luck.