The optimal time for one-time hedge trimming is mid to late June for all topiary shrubs. The only exception is boxwood and hornbeam and copper beech. These three plants are better cut in July. For yew, you can prune from June to July.
Missed the time, now what?
If you missed this plant pruning, you can still make up for it easily. Only from the end of August/beginning of September you should leave the shoots. Otherwise the plants would sprout again and the young branches would suffer frost damage.
Figures & clear edges = 3 x cutting
If, on the other hand, you want to cut figures or have an exact hedge in your garden, you will have to cut the plants more often.
- Boxwood: The first pruning is done in May, then in mid-summer and possibly again in late summer. Do not cut in mid/late August, as this will encourage sprouting once again. Then better in mid-September, when shoots still survive. Boxwood tends to frost damage very quickly. As soon as the danger of frost has passed, remove the dried and frostbitten shoots.
- Yew: it is cut the first time in June and then again in August.
- Cypresses: they grow much faster than yews and therefore need to be pruned 3 – 4 times a year. You can start in May/June and then every month until the end of August.
- Privet: Privet is also fast growing. You can prune every month from the end of June. Just like boxwood, you should wait until mid-September for the last pruning (i.e. not mid/late August), then the winter damage will be less severe. A radical “rejuvenation pruning” is allowed just before the first sprouting in April. Privet then grows all the more vigorously.
- And another thing: Dense, large hedges may/should be cut only after the breeding season. This is completed in May/June. If you want to cut earlier, you must make sure that there are no nests in the hedge.
Generally, June 24 (St. John’s Day) is considered the deadline for hedge trimming. Then the main growth is completed and the plant can be kept in shape even with one-time pruning.