Answer: Holly trees normally develop a pleasing and roughly symmetrical shape all on their own. However, if you prefer the look of a clipped hedge or need to keep the plants in bounds, you can trim them at any time from spring through late summer. Trimming in the fall may stimulate fresh growth which will not have time to harden sufficiently before winter. The nicest result is achieved by individually pruning out selected branches rather than shearing the whole plant. You will notice over time that the plant branches and grows denser at the site of each cut, so trimming actually makes it grow thicker.
Q&A Library Searching Tips