I agree that yard work is phenomenal for mood, but it is sort of captured in the article's list. I see yard work as a combination of light exercise, time spent in nature, and meditation. In your case, it's a personal hobby too!

As an aside to your last thought, there's a local teacher in my town that offers to paint home interiors in the summer time. He expects customers to do all the prep work and acquire the paint, but he will show up with brushes, rollers, etc. He does charge a fee, but it's much lower than any professional. When I asked why he does it, he simply answered that he loves painting and finds it relaxing, so he decided to do it on the side to help locals out. Maybe you could do something similar for yards in the neighborhood.