I grew up surrounded by nature and I love being in nature. Especially in the woods and parks. The combination of trees and their brunches makes the ideal composition, which you cannot stop admiring - wow! how could it be like that!
A small sketchbook or any kind of a pocket notebook, a pencil or a few of them, maybe some colourful pens or markers in your bag is more than enough to make a quick sketch just in few minutes or less. You are not wasting any time, while waiting for a friend running late for a walk on a sunny Sunday afternoon, or while sitting to rest on the bench walking the dog.
If you see some nice, I prefer to say some interesting, bushes or a tree at the bus stop, don't hesitate to grab your sketching materials and make several strokes, dots, on whatever caught your attention. Nobody is criticizing you and nobody knows what are you doing, - it is your personal emotion being transfered on the paper! I am pretty sure, when you come home and open your sketchbook to see what you have done, you will be even more surprised! Don't expect there would be a realistic tree, no way ! But you will remember that moment, your mood, what the weather was like, even more other details. Your family or friends would be impressed, how could you done such a vivid small drawing?! Maybe your own masterpiece!
This is one of the ways I teach my students to make the basis of the abstract art.
Maybe you think it is very easy, just pour the paints on the canvas, mix them with a cleaning brush..In my opinion, the really good abstractions are not so easy to make.
Just look around, notice, observe and learn! It will help you a lot later on when painting your abstraction at home or in the studio.