Given the severe winters in Maine, I'd think that you would be safest using trees that are known to do well in your conditions. I'd be asking these questions at a good local nursery, or consult your state's Agricultural Extension Service. Driving around your town and looking at trees in similar circumstances/exposures would also give you a more reliable starting point.

I'm certainly out of my element making any sorts of recommendations for USDA zone 5 conditions, so won't offer any specific advice on trees. The standard advice on spring flowering trees such as Magnolias would be to select cultivars that are latest blooming to avoid spring frost damage. Not a concern here in San Francisco where the Magnolia soulangeana cultivars are in full bloom for a month now.

Excellent advice as usual from Bahia. Although not fast growing, you might want to consider Amelanchier. Generally, fast growing does not go with better, smaller trees...

Watch out for cedar rust affecting the flowering crabs and ammelanchier. This is a problem where I am and if you have a lot of Eastern Red Cedar in your area, as I think you do, it mught be a problem there as well. I'm not sure that you have a problem with anthracnose with flowering dogwood up there or not.

My choice would be kousa dogwood which has the added benefit of blooming later in the year and has a nicer shape than the magnolias that work in zone 5 in my opinion. Also a nice red ping pong ball sized fruit later in the year (edible). I prefer the single trunk over the clumps.

Thanks, folks. My choices so far have all been from local nurseries catalogs.... there's not really anyone there to talk to this early so I'm just catalog shopping. I know people on my road grow all manner of Magnolias (saucer and star) but they're mostly people with professional gardeners, so just the fact that they look great in the neighbors yard doesn't mean they're right for me :)

I did notice some of the nurseries catalog entries noted "very disease resistant" Malus varieties, so perhaps thats due to the cedar rust. I'll have to look into that. We have two very old, very overgrown, very tall crabapples in another part of the yard: what does cedar rust look like?

Ammelanchier looks great! Love that it has fruit and fall color, too. It might be a little big for my space, but will investigate further... thanks for the idea!

Cedar rust looks like orange slime in the part of its life cycle that lives on the cedar. I'm not sure what it looks like on the crab in detail other than to say that the crab looks like it is struggling to live. If yours look fine, it is probably not an issue in your area. We never had a problem with it in suburban Boston, but down here on Cape Cod few people attempt to use flowering crab because of it. It is actually called "cedar-apple rust".

Here is a link that might be useful: cedar - apple rust

Thanks! I will have to look more closely at our old crabapples this spring. I didn't notice anything last year (our first in the house) but I wasn't looking very hard and they ARE very scraggly. There certainly might have been spots on the leaves that I didn't notice.

What about Redbud (Cercis Candensis) ?

Another small flowering tree ... hardy in zone 5 ... white, pink, or magenta bloom, ... and fairly resistant to disease.

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I was going to suggest redbud (Cercis canadensis). All the others listed have issues...at least they do down here in NC. The Native Dogwood (Cornus florida) ise susceptible to dogwood anthracnose. Korean Dogwoods (Cornus kousa) are resistant...but I don't know if they'll live up there. We've already covered cedar-apple rust problems in the malus family.

I have no experience with deciduous magnolias in Maine...but I can tell you that when I lived in Ohio we rarely saw them bloom in all their glory. They'd get started...and then get blasted by a late winter freeze. It was sad.

Redbuds are made of hardier stuff.

Thank you! Will look into Redbud as well...

If you want some of the Magnolias, and you have seen them in neighbor's yards around your town, and know that at least some of them are reliable bloomers, I wouldn't rule them out. If there is a good retail nursery that has a good selection of flowering trees, I'd spend some time talking to a real person rather than base your decisions of catalogs. The personal experience can really count for a lot. The Dogwoods and Malus can also have problems here on the West Coast, but there may be selected forms or species that are known to do well in your local area. It will pay to talk with other homeowners, maybe leave a note on their door asking if you might talk with them about the trees you have been admiring in their gardens... Wouldn't hurt to ask.

There are hundreds of kinds of flowering crabs. Regional performance varies with kind, same as with orchard apples.

Here is a link that might be useful: b849 - Powered by Google Docs

there is a "somewhat new" crabapple that is immune to the usual crabapple diseases. I can't remember the name of it but it is a red flowering one. I have had one for a couple years and it is gorgeous in bloom. It doesn't seem to have any problems at all and is very hardy. If you are interested at any point, I can look up the name of it.

Many disease-resistant crabs have been selected and put on the market. Which diseases they resist, and how much they resist them varies with each kind.

And each region.