Ask about this at your local USDA Cooperative Extension Service office (they will have web pages up). Especially since your USDA zone is so very low I suspect it is too late for this year. But you should ask them.

I like winter rye as a cover crop but I'm not sure how it would be as a lawn. It will stabilize your soil over winter but I think you would have to kill it before planting your lawn grass seed.

Mowing doesn't kill it unless you wait for it to develop seed heads and that could be May or June up by you.

Yes. Maine, I believe, is a special case like the Pacific Northwest. The two problems with seeding in the spring are germinating summer annual weeds like crabgrass, and problems with the new grass not tolerating the summer heat. I think Maine would be an exception to both of those issues. Go for it.

When you seed in the spring, DO NOT topdress or bring in more soil unless you really need more soil to correct a poor drainage issue. If you have water pooling in the center of the yard, then add more soil to bring the center up to a very slight crown. Water should drain away from the house, especially if there is a basement. If you bring in more topsoil when you don't need it, then you increase the chances of rainwater backing up into the basement. Excess topdressing is a peeve of mine. It seems like a universal problem including here at the house I bought last year. No basement, but there is definitely an inch or two rise as you walk into the grass that should not be here. So you might not have the problem, but it seems that the "professionals" who install lawns always want to bring in more topsoil. You don't need it.

If you are going to plant rye, take this opportunity to use an organic fertilizer on the lawn. You can use a commercially bagged fertilizer or you can simply get a bag of soybean meal at your local feed store and apply at a rate of 15 pounds per 1,000 square feet. Organic fertilizers provide food for the microbes living in the soil, and the microbes generate plant food for the grass. If someone tries to dissuade you from using organics as the temps cool off, ignore them. Now might not be the absolute best time of the year, but there is something magical (i.e. unknown) that happens with the soil biology in the winter resulting in a springtime flush of new growth even without traditional fertilizer. It's all biological, so you may as well give them a meal prior to hibernation.

I would use a perennial rye instead of winter rye. Better yet google for a Pennington Seed dealer locally and find a recommendation for a mix. Something with maybe some bluegrass and maybe some fescue.

I don't know planting grass in Maine but I have planted it here in PA in early December and it sprouted. I think I was lucky and it was only the mix of perennial rye that sprouted and none of the bluegrass or fescues, But if you cover the seed it'll sprout in the spring. I'd cover the seed with mushroom compost, maybe an inch thick. Also if I added more topsoil I'd first mix some mushroom compost into that. If you're shoveling it into a wheelbarrow, just add 4 or 5 shovel fulls of soil and then a shovel of MC. By the time you dump it and spread it; it'll be mixed enough.

Winter Rye is a weed in a lawn; not nearly as bad as Bermuda Grass like you find in grass seed sold at the big box stores.

Winter rye is a cover crop, used to improve soil tilth and fertility and deter erosion. It is NOT intended to be a lawn replacement. Too late for successful turf grass seeding now.

Please listen to dchall.....he knows what he is talking about :-)

(Wild rhododendron, by the way, grows north of you in all the Atlantic provinces. It's perfectly happy in zone 4 and even zone 3.)

Thanks everyone!

annpat can you share anymore rhododendron info? I’ve never come across it before (aside of south of here).

I know nothing about growing plants in Maine but the comment about Bermuda made me chuckle. If it were not for Bermuda non-irrigated yards in East half of Texas wouldn't have yard turf. Bermuda is about the only turf that can withstand foot traffic on ball fields and golf courses..

Bermuda grass is fine where it's the only grass that will grow. But to put the seed in a mix and sell it where fine grasses will grow should be a crime. My neighbor built a new house on the lot next door and did the landscaping himself. I told him what grass was appropriate and where to buy it locally; but he went to the big box store and bought a mix that would grow anywhere in the world. It's now all over the neighborhood. It's spread hundreds of feet into the woods. At least 10 acres that I know of. Three foot high weeds choking out the native plants in the woods, the flower beds, some of the pachysandra beds. Choking out the vegetable gardens. Making pulling weeds a massive job that destroys the plants being weeded.

nobasil, I doubted you and googled it. I knew that they grow in zone 4, because I've seen them.

It may not be the cold, but the soil. Rhododendrons require acidic soil to grow at all satisfactorily. Many people assume that all of the northeast contains sufficiently acidic soil for plants like rhododendrons and azaleas to thrive. These people are wrong. There are a lot of lime pockets in the northeast. Then there are the lime areas. The Champlain valley, the Upper Hudson valley, and the lower Mohawk valley all contain soils with a pH above 7. I'm guessing you are somewhere in the Champlain Valley, so when you head south, you are also moving east of the lime.

It has to do with the system of lakes and rivers that developed near the end of the last two Ice Ages.

I agree that you should contact your local extension office - it is often affiliated with a local or major university in the area. They should have all of the recommendations that you need for your particular locale, including what to plant for your permanent lawn.