"Tom,
Was Ross behind the Sycamore plantings at Gulph Mills near tees?"
Tom Paul's response:
That's a good question the answer to which is probably unknowable at this point. However, in his book "Golf Has Never Failed Me" he did say on the chapter on trees;
"On hot summer days they are most welcome, especially around tee boxes."
That remark from his book anyway couldn't have been known when GMGC was built because that manuscript did not surface until pretty recently. It was in the possession of McGovern or perhaps his daughter. It was written in 1914 so maybe Ross mentioned this to GMGC in 1916.
From the 1924 aerial of the course all the tee box sycamores can be seen and although small they weren't that small, so yes they probably were planted initially and it's pretty logical given what he wrote in 1914 about trees and tee boxes quoted above that he probably recommended it.