Nothing - it's waiting for the weather conditions to be right. The one we have in the gardens downstairs is in the same state. I have seen others round and about in full flower already, but the environment around the plant dictates whether its warm enough for the flowers to open up fully. Where ours is, its subjected to northerly and easterly winds, maybe yours is too, so its just waiting. It'll open up at some point, unless the flowers get completely killed by heavy frost. The only exception is if the plant's really dry (say in a pot) when you should water, but the way the weather's been , I doubt that's a problem in the ground.