The way to achieve a starburst, without a special filter, is to set the camera to f/16 or f/22, and then meter off the trees without the sun in the viewfinder. That way the trees are exposed correctly, and the very small f/stop will bend the light around the blades of the shutter to create the starburst effect.

Sometimes I like to look up at the trees, rather than straight on; it can sometimes make for a compelling image.