What is a fast growing tree?

what is your location and lighting?

Soft maples are fast growing. But also not a real strong tree so don't plant close to structures

Most pines are fast growers.

Hi! Here is a site by HGTV that lists and shows pictures of fast growing trees.

Enjoy! http://www.hgtv.com/outdoors/flowers-and-plants/trees-and-shrubs/fast-growing-trees-pictures

Without knowing where you live and why you want a fast growing tree, it's hard to say. Fast growers are also short lived. Silver maple grow fairly quickly but have only @ 25 year lifespan. Perhaps a tall shrub would be better?

Hybrid Poplar is a very fast growing tree. I had two planted in my backyard. However, they are in the Cottonwood family and give off hundreds of fluffy things that looked like cotton balls and flew all over my property. Needless to say, I had them removed and replaced with a Red Sunset Maple, a truly lovely tree in the fall when the leaves change color.

I find Maples are fast growers. What is your gardening zone?

almost any kind of maple tree is fast growing. Clevl Pears are very fast growing just a softer wood.

Mulberry. And they make wonderful climbing trees. Just don't put them where you don't want their fruit to drop and color whatever is below. Squirrels and birds love them (so do we).

poplar