I bought bamboo from the dollar store here, and they turned out to be a real nurture center for mold at some point in the season... Used bleach to clean em and re-use, but by the end of the second year the part that was in the ground was looking streaky and year three the in ground parts were pretty funky with white mold. It did not seem healthy to put that close to anything, and bleach treatment wasn't really staving it off. (Pun!!!
) So I tried a couple of kinds of paint on a few of the staves - one was an enamel the other a 'rust paint' of all things. I was using the rust paint on some metal cages and decided to try it on a few bamboo as well. The rust paint worked. It's pretty tenacious and season two of it not seeing any damage. The enamel otoh started to rub off after one year.
So... I think the right finish may help to extend their life, but without a coating, they will rot pretty fast.