Just a couple of quick comments:

Neither wax myrtle nor crepe myrtle, despite their somewhat misleading zone ratings, are well adapted to life in MA even in a Z7 area. They are likely to suffer from extensive dieback each winter and will never look like they do in the South.

All trees except for sterile hybrids bloom. How messy their spent flowers are varies from species to species but should not present any sort of problem on a lawn that is mowed.

No tree or any other plant for that matter, stops growing when it reaches its mature height.

Good local nurseries, your County Extension Service, state agriculture department, UMass are great sources for information about trees that will do well in your particular area and meet or partially meet your criteria.

How about something like acer gresium, paperbark maple? I havr never seen a large one and they have interesting bark. Mine does not pit on much of a show in the fall and seems cold hardy but somewhat slow growing.

Redbuds? I should know their scientific name there are a dozen between me and a neighbir here. They have a bit of a yellow fall color but do flower. No big magnolia type petals. Their seed pods do not seem to bother any of my neighbor's dogs.

how about a pergola patio setup ...

create your own shade and privacy ... immediately ....

all of your wants and needs.. seems to make just about any plant fail in the long run ...

do understand.. that no tree ever really stops growing ... and the ones that limit out lowish.. take decades to get tall ... and ones that get tall fast .. arent going to stop at some magical height ...

we all want the perfect tree.. for any given situation ... rarely does anyone find it ...

good luck ...

ken

ps: you cracked me up.. how many times you worked the word 'fiancee' into the post... congrats.. i remember those days ... lol

Here is a link that might be useful: link

mainegrower is quite correct; although if your heart is really set on a Crape Myrtle you should check with the Polly Hill arboretum to see if any cutlivar or more like species (i'm thinking a very hardy selection of L. fauriei *might* be floating around out there) had matured there and remains reliable mature. With a smaller yard (it would be different if you had several acres for a mini-arboretum) you do NOT want a shade tree that will potentially die back every 5-10 years.

"During the hot, humid, sunny days of summer, this is not very pleasant. " - on Cape Cod!? My God! If only you knew what unpleasant really was!

Acer griseum is a good suggestion but they are slow early on, or so I understand; some hybrids of them grow faster. I think they turn yellow. I'm not sure I can recommend it in this case it but I will note that my Lacebark elm ('Allee') always turns a somewhat pale yellow, and later than other trees so that's kind of interesting. I have the impression you want something that can get fairly large fairly quickly, and the lacebark elm certainly would...but as mainegrower also said, no tree is going to get to the height you want and just stop. The lacebark might get too big for your taste.

Ken, I want to disagree politely. I contend while a redbud (or other tree) will never stop growing its vascular system or structure or genetics do effectively limit their height.

On the extreme and more spoken about end, think of the tiny foliage on top of both of the native redwood and sequoia. I just don't think 500 foot is physically possible out of either unless one starts growing alongside a 300 foot cliff then a branch contacts the soil and roots itself at a height of 300 feet.

My Shingle pushes out about six inches of growth a year still at 90 foot tall but stuff breaks off it all the time.

More notably, no southern magnolia in Missouri is taller than the tree listed on the big tree champion tree and there is a common height they just do not get past.

The dwarf world is different and beware of that. While the listing for a sycamore might tell me it will get 80 feet tall which is common here, many of the pines will list a ten year height. And what do you know, year 11 it will be six inches taller lol.

So I think it is safe to plant many of the smaller trees and if your yard happens to be the 1 in 10,000 best site ever for a redbud and you get the national champion in sixty years oh well lol.

Thank you for that tip akamainegrower. I will definitely not plant those trees if they won't do well in Massachusetts. Definitely wouldn't want to plant something just to have to get rid of it because it didn't make it through the harsh winter.

akamainegrower and ken_adrian, I'm not sure what you mean by no tree stops growing when it reaches its mature height. If that were true we would have trees thousands of miles tall. Maybe I'm misunderstanding you? Sorry LOL

tornado3800, thank you for the suggestions. Unfortunately I don't like the look of the paperbark maple, and we don't want a tree with pink flowers, which the redbud has. :/

ken_adrian, thank you for the "congrats" :) i didn't even realize i said it that much LOL

davidrt28, it does actually get pretty hot over here in Massachusetts in the summer time, with temps often up in the 80s but "feels like" temp in the 90s, due to the super high humidity. Yesterday I didn't even want to go outside because the air was so thick and humid, it was difficult to breathe. Although, I would much rather have this weather than the bitter cold temps of winter with its cloudy, dreary skies. The lacebark elm would probably get too tall for us, but thank you for the suggestion. :) We have solar panels on the roof we don't want to block the sun from shining on them.

We still are not sure what we want to plant in the corner and middle of the back fence, but we think we found a tree to plant in a row along the side fence... the Crimson Pointe. What are your thoughts on that? I looked it up, and it grows in our zone, meets our criteria for "mature height", and my fiance likes it a lot, even though it flowers (finally one we both like). We would plant several in a row for privacy on the side from the two-story neighboring house. Does anyone know what the growth rate is like for a Crimson Pointe? I attached a picture of a row of them I found online.

Thanks so much for all the tips and suggestions everybody :)

I'm not sure how to upload more than one photo in a post, but here are some more pictures of my backyard, I figure that might help. I took these photos at about 6 PM, and all are at eye-level standing up. This first one is our "lovely" view of the two-story house on the side of us.

And here is our "lovely" view of the house behind us. We can see right into his kitchen window the second we step out the back door onto our patio. That is the 3-pane window on the right. We really want a tree there to block this guy's kitchen window. His wife has called out to me to talk to me while I was in my backyard and she was in her kitchen. It was quite awkward...

Trees don't ever actually STOP growing. However, they will slow down a LOT once they reach a "mature" height.

A tree that might grow 3-4 feet per year when it's 10 years old might only put on 2" per year when it's 150.

Redbuds are and excellent suggestion. The flowers are not a problem as the will sift into the lawn and not need raking. You may want to look into a variety of Tulip tree called Emerald City. It is a lower growing type of this American native. Consider also the tree lilac Syringa reticulate. It does bloom, but like the Redbud, the flowers are small enough not to need raking. There are also varieties of Honey Locust that will stay small.

I stole this from another poster on another post, but it is a good one. Thornless Honey Locust, Gleditsia Trithancos.

Be mindful an evergreen perhaps could be limbed up a bit (once the plant was taller & larger, and could spare the limbs), so the foliage wouldn't have to come down to the ground. This fact may open up some possibilities for you.

I don't know what grows well in your area. Trident Maple is somewhat similar to Paperbark Maple, from what I've read.

If you decided the budge on the height concern, fastigiate European Hornbeam might be a nice looking tree.

As for flowers falling on the lawn, not all flowers are created equal. Compare the flower or similar structure of a Magnolia with a Dogwood or Redbud and see what I mean.

Richard.

Here is a link that might be useful: Fastigiate European Hornbeam