Fertilizing shouldn't be relevant. If flower buds are forming then not opening something is killing them. Too cold? Birds eating them?

i planted a tiny stick .. took it 5 years to have one single flower.. and handful the next.. and then finally the whole tree ... 7 years ...

you say it was mature when you planted.. shall i presume ball and burlap .. wherein every single root of your mature tree was severed for balling???

if so ... you will have to wait.. until it regrows a root system sufficient for it to waste a lot of energy on flowers ....

if it is in the middle of the lawn.. high nitro fertilizer.. used on the lawn.. could interfere with flower production ...

bud set is in fall the year before... if the tree was somehow impacted in fall.. drought.. too much lawn fert.. etc ... the flower buds could have aborted..

as well as a hard frost in early spring... but one would think the flower production would be reduced.. not entirely destroyed....

more facts ... like how it came.. how it was planted.. and how you have cared for it since.. might be helpful for more precise answers ...

but sometimes it just comes down to the tree doing it.. when the tree wants to do it.. and nothing you can do is going to speed it up ...

IMHO ..NEVER fertilize a tree .. waste of money ... if not downright harmful if done improperly ...

ken

You can try adding some potassium or bone meal, the soil could be deficient and the only way to tell is to get a soil sample analyzed but if everything else is okay it just could be it is not ready yet.

Here is a link that might be useful: Propagating Perennials

'Snofozam' being a vegetatively propagated clonal cultivar, all specimens have the sexual maturity of the original parental specimen. Stock of all sizes at outlets here drips with flowers, not matter how light a grade.

It's possible that a frost may have gotten to it...but I feel it's more likely that A) it may not have enough sunlight...and B) it may have been over over fertilized...this would cause the greens to be very showy, the plant to grow tall and healthy fast, but not to flower...cut back on the fertilizer earlier in the fall, and if possible, move to a sunnier location while the tree is dormant (early spring or late fall).