Treated Pine Pergolas are made of #1 Grade Southern Yellow Pine that has been pressure treated to resist decay and insect damage. As with all of our treated wood products, the wood is "KDAT" (kiln dried after treatment) to make sure it stays flat and does not bow or twist. The process also limits checking (small hairline cracks that will appear on unfinished wood when the surface dries over time). We highly suggest that you seal the wood regularly, every one or two years depending on where you live, to maintain its appearance. But if you prefer a more rustic look, you can allow it to gray and still keep the protection from the elements. Treated Pine can also be stained or painted. Most store-bought treated lumber cannot be painted for up to a year after purchasing, but since KDAT is drier than most store-bought treated lumber, you can paint it immediately.