Ok, two years ago planted a hedge of Green Gem boxwood. Planted them so they touched, they were already decent size at the time, maybe a little over 1 foot tall and wide. Big mistake. Huge. This year, they were not happy, had some browning either due to winter damage, retarded root growth, or lack of water. Take your pick, could be any reason, we neglected them last year due to other priorities. We also had them too close to the retaining wall, could have been root exposure. In any case, we were being impatient and planted them too close. We dug them up, a chore, but the burlap was still intact - the roots hadn't even established. We removed one from each row to allow more room for growth. We also added compost to the soil. Normally, I would not prune any plant at planting time, but these had so many dead branches because they were packed so tight, we had no choice. So, we trimmed them down to a low hedge. I would say, space them properly if you can, you will be rewarded in the long run. In my experience, in my zone, Boxwood have done fairly well for me as far as growth rate, and I have clay soil. I have some in shade, some in most full sun, and aside from my overpacked hedge, they've all done wonderfully. In other words, they will grow faster than you might expect. Ideally, in future years, it is appropriate to prune/hedge boxwood in mid june, no later than mid July to give them time to harden off before winter. Also boxwood like to go to sleep for the winter with wet feet - I run a soaker hose mid November - this is the last of the moisture they will receive. I protect mine from the sun with pine sprigs in the winter months, or burlap works fine, and I spray them with wilt pruf in November after watering to help the foliage retain moisture. I have Green Velvet - love it, nice mound shape. Green Gems are more compact, they have done well for me. I also have green mountain, takes to shearing/hedging well, but will also grow into a nice upright form if left to grow naturally. My Green Velvet, on the north face of my home reached a nice mature height going on the fourth year - BEAUTIFUL. I have planted two more, for a set of three. Love them. Water daily for the first two weeks after transplanting, then weekly until well established, for the first two years.

more leaves.. means more food production.. means faster establishment.. which means faster growth ... take away half of its food production capability .. and you may stunt it.. i vote for letting them be for another year or two ... ken

I thought privets were impervious to pests and diseases. When the leaves get really old on my texas privets, they yellow and fall off. If there is yellowish veining in the new leaves, it may be a nutritional deficiency of some sort, but if the interior leaves are bright yellow, they are just old and will drop. Shear your privet if you want a narrow thick hedge. Make sure you shear the top as well so that the naturally long arching branches send out new little branchlets. Just shear it a bit higher each season. I am growing privets for privacy now, and once I get them dense and tall I will stop shearing and let them go wild. I like them best when they are allowed to grow into their natural shape. Fortunately, we do not have a problem with them reseeding in our dry climate. Renee

So, you need something about 18" tall and 12" wide, in part sun in foggy zone 15. You may also need something very shallow-rooted, because the hedge plants may have filled the soil pretty solid with their roots. How is the soil there? You may get new growth lower down on the hedge by pruning the hedge narrower at the top. This would allow more light down to the bottom of the plants, allowing for stimulation of new growth. More light and extra watering might get you more growth down low. Another option would be to try pruning one plant almost down to the ground. It may come back green all the way to the bottom. Trim it narrower at the top than at the bottom so the base gets sunlight, enabling the base to stay foliaged. If it looks good, you could do that with the rest of the hedge. Being already a well-established hedge, it's going to get back up to 4 or 5' a lot faster than baby plants would.