Bearded dragon not eating greens?

I have a two and a half year old BD. He gets fed crickets and dandeline leaves, he wont eat much of anythihg else. I am at a bit of a loss as I cant keep feeding him only crickets as its not balanced. I put fresh dandeline leave,carrot peels,a few pieces of diced apple/g/basil leaves, in his tank daily since he was young. He went through phases of eating it, esp the dandeline leave but not lately, all he eats are the insects. Logicially if he is hungry he will eat this veg if he doesnt get crickets so I have tried two days of leaving fresh veg but feeding no crickets and he has eat a leaf or two but nothing else so he knows its there and knows he can eat it but he's not bothered. Its hard not to give him crickets but I dont know what else to do to encourage him to eat his veg. He needs the nutrients they provide. I tried reducing the crickets and placing them in his veg bowl etc. What do you do when a beardie wont eat veg....he is eating crickets well,he is healthy etc but wont eat his veg....