I'm building a pergola in my backyard covering the entire patio, see pictures. I want to next put up some bamboo poles to fill out the space between cross beams. In shopping for 2" diameter bamboo, I saw several different types: timber, tonkin, carbonized, black and/or speckled...etc. Each vendor touts their being better, hard to know who is to believe. Do you know what bamboo type that is in the third picture? Thanks,