Q.How Do I Prune Eugenia Into A 15 Foot Formal Hedge?
I planted several Eugenia myrtifolia ‘Monterey Bay’ in February. My goal is to prune them into a 15′ formal hedge. When do I start pruning so that they will fill in up to the my desired height of 15 feet?

Certified GKH Gardening Expert
You will want to prune to your desired height, and keep it there with occasional prunings. This is the most common method. You can prune at several times per year, but it is best when the temperatures are mild.
Here are some articles that will help:
https://www.gardeningknowhow.com/ornamental/shrubs/eugenia/eugenia-hedge-pruning.htm
https://www.gardeningknowhow.com/ornamental/shrubs/eugenia/eugenia-hedge-care.htm