They are safe, if they are from API... Also, I agree with Batman And Kim, 100%. Bettas need a lid so they don't jump out, they need a heater, so they don't get cold and become lethargic, they need a filter to pick up all the detritus and fish poo left behind, and IMO, a tank of minimum 5gallons.
BAMBOO IS NOT THE ONLY AQUATIC PLANT!!! Just making sure you reread that... There are so many other species of aquatic plant, I can't remember them all......... There are at least 600 species of aquatic plant currently known... And many of them can be bought from your LFS, if it is a quality fish shop... and I agree with Batman again on the amount of aquatic plants their are.........................................