Welcome to the forum I'm not sure of the tree, but those round growths look like galls (kinda like benign tumours). They can be caused by a variety of things - fungus, bacteria, pests, etc. Hopefully someone will be able to help with the ID
Not knowing the area you are from I am going to guess that it is a cotton wood tree and the green bulbs are the fruit capsules. There are many species of cotton wood throughout the U.S. so I can’t tell you which one it is.
Yes, a Fremont Cottonwood (Populus fremontii). I'd like toto identify those stem galls... Possibly young galls of the aphid, Pemphigus populiramulorum, but I'm not sure.
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