Chrysanthemum buds not opening up

My Chrysanthemum plants have lot of buds, but not blooming for a long time.  What would make the buds open up?

Thanks.

which variety of chrysanthemum are you cultivating and how many days old . 

variety: pache
planted in: First week of March

Thank you Sir,

Spray Planofix Harmone. If any thrifts are seen Spray Monocrotophose .

spray GA3 i.e gibberlic acid available in the market or with scientific suppliers shop add 100mg in 50ml alcohol or any liquors available and mix with 100liters of water and spray with power sprayer definitely it will bloom.TRY AND POST YOUR RESULT     

I had GA sprayed twice based on the suggestion from fertilizer shop, but did not see any change for almost 4 weeks.  However finally in 4th week, the flowers have started to open up.  Not sure if the result is because of GA or it opened up naturally due to change in environment - it rained here.

Yes it is of GA