For anyone thinking about biking to Boston from Needham, you might want to check out the Southwest corridor park system, which provides a lovely bike path from near the Arboretum all the way in to Northeastern University and beyond.
The corridor actually runs all the way to Copley Square, though you need to make an unmarked left turn on Camden before Mass Ave to find the continuation of the park on the eastern side of Mass Ave.
If you map a route on Google Maps, using the bicycle route option, you will likely get routed right through the Arboretum, which is itself a lovely (though brief) portion of the route.
The bike path runs along the same corridor as the commuter rail and the Orange Line. It’s well-marked, and well maintained.
From Kendrick St. in Needham the route through the Arboretum and along the SW Corridor is about 10.5 miles to Copley Square.