While I did a fishless cycle with minimal plants by adding small controlled doses of ammonia, few have the patience to do this.Wow! These are all very thorough responses. Thanks for sharing your knowledge! I think I can see why there are misconceptions about tank cycling as well. Thankfully these responses helped clear these up!
Bettas are very hardy fish if you had any ammonia it wouldn't bother them as much as other fish, look how the fish stores keep them in little cups. If you are feeding sparingly 1 betta with heavy planting the plants should consume the ammonia. That doesn't mean the tank isn't developing BB and doesn't mean the cycle isn't completing.
If you plan to add more sensitive fish, wait a few more weeks and do so slowly. Getting an API Ammonia kit and testing will help, don't do a water change for 2 - 3 days and then check your Ammonia, if you don't have any or 0.25(test is poor at distinguishing between 0.25 and 0) you are fine. Classicly if the cycle is completed you should have 0 Ammonia 0 Nitrites and be building up nitrates slowly. However given you have plants and a low bioload you may never see the nitrates build up.