Loves, I've never heard of a jasmine gardenia..is it a jasmine or gardenia?
Most likely, if buds are turning black it sounds like soil is too dry..also, gardenia's prefer acidic soil..acidic but well-draining. Is your plant in the ground or pot? Toni

dear hopefulauthor, (toni)
thanks for the reply. first, it is a gardinia but here it is called a jasmine(ian) gardenia. second , it is in the ground.could u please tell me how to check for acid levels? do i use a litmus stick or what?
meanwhile, i am giving it more water.
hope u had a nice 4th.
lovesgardening (dory)

you need to have a soil test performed to get accurate results. here, one would probably get it done at the local extension service. i don't know what resources are available where you are.
the plant previously had the botanical name of gardenia jasminoides but now it is gardenia augusta (i think?).
that is probably where you heard or saw the reference to jasmine.
this link addresses bud drop and other problems of gardenias.

Here is a link that might be useful: gardenia culture