Ponderosa fertilizing, needle length and backbudding

I acquired two In the fall ‘17. Fertilized heavy that fall and this past year. One PP had 7 back buds while the other larger old PP is just now showing a few emerging buds. Needle length on both are fairly long and anticipated. Structure is set on both trees, ramification even just a little will really set these trees up but if I continue to fertilize this year it will be another 4 years before needle length would be specimen quality.

Here’s the question. Can you get backbudding on old PP’s when not fertilizing until new spring growth is harden off late summer?