Every garden needs a few. They can be funny and punny, or as a nod to a special gardening friend.
I save up bits of old siding, torn off a wall in a renovation, or beg for the scraps from a fence or bit of construction. Mike knows that I will keep these in the greenhouse and there they'll stay until inspiration strikes.
The motivation is the opening of my booth to sell garden art and porch decor. I'm building up stock of all kinds of interesting things. You can see more about it here.
This is how I make these signs, and it's important not to get too precious with them. Sanding to take off the rough edges is fine, but don't get carried away with making them perfect. They are meant to be rustic, after all.
The really rough spots, like the nail holes which are splintery are smoothed with a rasp. Then a coat of my favorite acrylic craft paint goes on. I used white, then the lettering is in black.
I use a small amount of water on the brush for the lettering, and go really slow. I can do more than one coat, sanding in between if I need to.
Once all the lettering is completed to my satisfaction, the whole thing gets sanded, and some of the lettering gets sanded off too, to make it look aged.
I may also give it a wash (a thin layer) of another color, like a tan or brown, just to give it even more weathering.