Painting trees even on a large scale isn’t as difficult as it seems. When you look at a tree you don’t see every leaf, but rather images of sunlight on patches of green throughout the tree. With an over-sized tree as you’d have in a mural, the key is scale. Viewing the tree in relation to its surroundings will help you decide on its size. From there, you can break down the design to make it manageable.
Estimate the size of the tree you want for the mural. Imagine it in relation to people, animals, or other objects in the foreground, middle ground, and background of the mural. Determine the size of the tree in terms of specific feet and inches.
Decide how much of the tree will be leaves and how much will be bark. If it’s a pine tree, decide how much trunk you want in relations to the branches with needles. Figure it in terms of feet and leftover inches.
Sketch out a rough illustration of the tree with a pencil on newsprint. Tape several sheets together if you need to. Cut out your tree so you can trace it. Tape it to the wall to make it less difficult to work with. Sketching it first gives you a better idea what your tree will look like, and you'll know the exact size.
Trace the tree on the wall. Remember that acrylic paint will hide light pencil lines, so don’t worry about them showing when sketching it in. Remove the newsprint and tape from the wall when you’re finished, and throw them away.
Paint the greenery working from the top down. Starting high allows you to catch any drips from your brush as they come down. Use wide, darker green brush strokes for pine trees since pine needles are dark green. Sweep the brush across, letting it taper off where the needles thin toward the ends of branches. For trees with leaves, use a sponge to apply foliage. Use a range of color to suggest highlights where the sun hits and shadows behind the leaves.
Paint the trunk next using a wide brush. Work with different shades of brown to make it look more realistic. Paint strips of color to indicate sections of bark and patches of color in other places to indicate sunlight or shadow.
Before you paint your tree, consider what is happening with other objects in the mural. If the sun is shining on the left side of what has already been painted, you want the sunshine on the left side of your tree. Instead of trying to paint every leaf on each tree, use big, broad strokes instead to cover a lot of area at once.