Keep any trimming above about 50% the original plant's height. I'd avoid cutting down too low if those lowest stems are fully bare.

Although, once the summer heat gets going, it should grow back quickly if soil is fertile and moist/warm.

Here is a link that might be useful: Burning Bush

I live in Newfoundland labrador and I have a burning bush which has about 1/3 starting to have leaves growing out of the branches. While the rest of the tree as of yet has no noticeable sign of leaves. Is there still a possibility to have leaves? If not, should I cut the branches away at this time where there is no growth? Or should I wait until the fall?

Lori