I'm having the same problem here, sparse blooms, very low ground hugging growth. Mr I suggested it hasn't been warm enough, and in my area that would probably be applicable. Our temps have been up and down and everything in between since I planted them 6 weeks ago. I've also been getting seed pods already, and that is definitely not the norm for me. I'm about to yank and replant from a different source before I lose an entire season to whimpy plants.
-Nan

Could it be too much shade?

Tom

Sounds like too much nitrogen. They bloom best with low N, and high P. Most Miracle grow has high N, which is why you're getting lots of foliage growth but not many blooms. If you're partial to Miracle Grow, you should make sure you have their 15-30-15 formulation and only use 1/3 to 1/2 the amount of MG to the normal amount of water. That should get your blooms going.

Deanna