Many common evergreen shrubs, like boxwoods and holly, are well suited to trimming into a formal privacy hedge. Although water and fertilizer are necessary for healthy evergreen hedges, it's the trimming that keeps them in top shape and looking their best. 

1. Trim Timing

Nearly all evergreen hedge shrubs can be pruned in late winter through early spring without any issue. The plants will be dormant or semi-dormant at this time, which means they won't suffer shock from the trim. The main exception is any hedges that flower in early spring. These should be trimmed right after flowering in later spring. Do not trim or shape shrubs during dry summer weather or once autumn arrives.

2. General Shape

Your shrubs can be pruned into rectangular walls, simple columns, or round humps, but there are a few guidelines to follow. The bottom of the shrub should be slightly wider than the top. This provides support and ensures that sunlight and moisture can reach the lower part of the shrub. The top should also be rounded slightly as opposed to perfectly flat. This allows moisture and snow to slide off, thus preventing the shrub from splitting.

3. Hedge Training

Training may be necessary for younger shrubs that aren't quite full hedges. Your trimming service will begin by putting in tall stakes at either end of the row of shrubs. They will then stretch guidelines between these stakes. These guidelines are used to trim the shrubs evenly. Depending on the type of shrub you have, your service may also use plant ties to help train branches to grow in a way that creates a better hedge.

4. Recovery Pruning

An overgrown hedge that hasn't been pruned properly for many years may require recovery pruning to get it back into shape. Instead of cutting off all the overgrowth at once, your service will instead trim back the overgrown branches incrementally over the course of two to three years. This avoids shock to the plant, and it gives it time to leaf out and recover between each major trim.

5. Summer Maintenance

Some ongoing trimming may be necessary in the spring and summer after the main winter trim. It's okay to cut back a few branches that put on too much new growth and ruin the shape of the hedge, just avoid heavy pruning. It's also best to stop all trimming a few weeks before the first expected frost. Pruning can encourage a flush of new growth, which won't be able to survive frost. 

Contact a shrub trimming service, such as Loof's Landscaping LLC, for more help.