Have you looked at Hybrid Poplars? They are arguably the fastest growing North American tree. There are lots of different ones so you would want to pick a shade variety.
Description:
Provides outstanding shade in a hurry! Grows 5-8 ft. every year until reaching mature 50 ft. height. Puts out plenty of side branches. Glossy foliage turns golden in fall. Resists cold, pests and disease. Thrives in most soils and climates.
Zones: 3 - 8 (-30� F.).
Height: 50 feet.
Shade Requirement: Full sun to partial shade.
Yes they grow fast but they are are messy, messy, messy! Also had the roots of one totally block up a 6 foot section of a 6 inch drainage pipe. The root forced it's way into a junction. It was a solid mass of roots!
