I looked back at my old Plant Data Sheets from the Saratoga Hort. Research Foundation one of the early proponents of "Ray Hartman". "Rapidly attains ten to twenty feet in height and width". "Responds well to pruning, it may be trained as a small tree". I do not think 10 feet apart is too far. Al

Ray Hartman wants to be tall, not wide. Does take off - will reach 10 ft. from a 1 gallon size in 2 years if happy.

My one remaining 11 year old Ray Hartman is probably 10' tall and 8' wide. I'd say it depends on how thick you want them to be along the drive.... they're not very dense, you know.

Well, thanks for your feedback everyone, I am still undecided, I really do want it to be a dense screen. What is the worst that could happen if i space them 7 or 8 ft apart rather than 10 ft?

I am thinking this way to be cautious because they do have to put up with a bit of competition near the property line from the neighobors established prunus, so I want something vigorous.

thanks , if anyone has more feedback.

You could plant them closer and grow as a screen, but as was said they are not really dense in their growth habit. I think you would lose much of their beauty and bloom and think other choices would be better for growing a screen. Al

thanks Al, I'll leave them at 10 ft. apart which I planted them at yesterday. Happy Labor Day weekend!