Growing bamboo is eco-friendly but the process to get it into material is not:
"The growing of bamboo is environmentally friendly but the manufacturing of bamboo into fabric raises environmental and health concerns because of the strong chemical solvents used to cook the bamboo plant into a viscose solution that is then reconstructed into cellulose fiber for weaving into yarn for fabric."
The FTC noted that the end product of cellulose is rayon (regardless of what the cellulose started as) and needs to be labeled as rayon. But there are some rayon exceptions that are more eco-friendly:
"However not all rayon is created equal; Lyocell, or Tencel, is made in a closed-loop process using less toxic chemicals. Like conventional viscose, it can be made from any form of cellulose including bamboo."Hopefully one day I'll write a longer series on fabric impact but I thought this was an interesting point to note now. Thanks, Treehugger.
"Once the stuff had to be called 'rayon made from bamboo' it didn't sound quite so natural and green anymore and pretty much disappeared. If you see bamboo clothing, it might be spun directly from the fiber and described as bamboo linen; otherwise, unless you see the Lyocell or Tencel label, give it a pass."