all bb's are degradeable and the bio bbs basically degrade at the same rate. I used those wallmart bb's and im still finding some perfically shaped ones from LAST year. If your worried about the bb's hurting the trees they won't do much so don't worry. if the owner doesn't want a crapload of noticable white bb's around just use black ones.
if your using the bio degradeable bb's open them 2-8 days before you game and then they should degrade faster. If you open them on game day expect them to degrade like normal bb's
hope this helps Cheers!