In a sheltered area like a porch ceiling, stained wood does very well. Make sure you use a good marine varnish with UV protection. We use Epifanes, but there are other brands. For best results, coat all sides before the boards are installed.

Pine is the usual wood in a bedrboard or v-grove profile.

Another option is to use vinyl with a wood look -- not as authentic to be sure, but no maintenance to speak of AZEK beadboard ceiling is reported to take paint and stain very well, and looks very realistic. We have not used it, however, and cannot speak from experience.