I think you should only use aged (at least 6 months) hard wood in your Smokette. The reasoning behind this is the same criteria you would use for burning wood in your fireplace or wood stove. Green wood not only burns hotter & faster but it will generate a heavier smoke due to the sapp still present in the wood. I think the heavier smoke would probably leave a bitter smoke flavor. That being said, you can probably use any hardwood if you use it in the correct amounts & achieve a decent smoked meat.