Drawing hands is one of the most difficult things to learn and it’s what makes the difference between an average artist and a master. The good thing is that you always have a model close by in the form of your own hands.
Even if you're living on a pension like some of my students, you have only limited time and energy for your drawing hobby. And if you are creating art as a profession then time and energy may be even more limited and valuable to you!
If you want to learn how to draw trees, begin your drawing with a basic sketch of branches, trunks (internal structure), and leaves (external structure).