Nellie Stevens Holly Is Not Growing. They Have Put On Only About 6 Inches In 2 Years. Help!

Question

These are 6 foot tall plants that have a single stem on bottom for a more tree like appearance. Have been fertilized with acid loving early spring and summer. All had blooms and now have berries. No sure how to get some height. Bought and planted for privacy. All are planted 6 feet apart as well.

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Answer 1

I know this variety is touted as fast-growing. I am guessing they need more nitrogen, and perhaps a yearly pruning. They only need a slightly acidic pH level, so don't overdo the acid. This article has some good tips for how to fertilize them:
https://www.gardeningknowhow.com/ornamental/shrubs/holly/fertilizing-holly-bushes.htm
and here's another with pruning tips:
https://www.gardeningknowhow.com/ornamental/shrubs/holly/trimming-holly-bushes-how-to-prune-holly-bushes.htm