There definitely appears to be some artificial lighting going on. Its either a sunset or sunrise shot, which means those top-lit flowers are being illuminated by something behind and above the photographer.
I think they also did a selective exposure boost (or vice versa) in post, since the light travels up the valley in a pretty unnatural looking manner.
I suspect its not HDR but an orton effect in play (or perhaps and ortonized HDR image, I've done that before).
Here are few orton shots that that shot reminds me of I've done in the past...
FWIW, those shots all took very, very little post work, its a pretty simple technique and can be tweaked to roder depending on how your taste for it goes. There are a lot of resources online that will step you through how to do it - the only trick after that is practicing until you find a way you like.