Answer: The kousa dogwoods are considered winter hardy into zone 5. Your zip code places you in 5A or the coldest part of zone 5. In an exposed and windy location this could actually be as cold as zone 4. For this reason, I don't think I would recommend planting this tree for you. Instead, you might look at some of the more winter hardy and robust flowering trees such as crabapples or redbuds (Cercis canadensis.)
A cluster can look lovely, you will want to allow enough space between the trees to allow them to reach their mature size so do not crowd them too close together as we are often tempted to do. Also, for the health of the tree's root systems it is best to leave the area around their roots mulched rather than planted. This helps the trees get a better faster start. Use an organic mulch such as shredded bark and apply it in a year round layer about three inches deep. Spread it out in a flat layer over the root area and do not allow it to touch the bark or trunk of the tree.
Enjoy your new landscape!
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