Artsy people - what kind of glue would I need for sealing leaves & gluing them to construction paper?

I want to make a collage of one giant leaf made out of many small leaves. I want to glue the small individual leaves to construction paper so that giant collage gradates from dark colors to bright. what type of glue do you recommend? I want to be able to seal the leaves so they maintain their green color currently and I dont want them to fall apart or wilt.....halp :3