When cutting back ornamental shrubs, three different shrub groups can be distinguished: Semi-shrubs (such as bluebeard, heather, lavender), ornamental shrubs with soil-borne shoots (such as forsythia, shrub rose, Weigela) and ornamental shrubs without soil-borne shoots (such as winged spindle, magnolia, rhododendron, cherry laurel and table dogwood).
Cut semi-shrubs back by two thirds to three quarters of their height every year. Then fertilise. They then sprout strongly and flower abundantly.
Ornamental shrubs with soil-borne shoots taper with long canes from the base of the shrub. These shoots thicken and branch off in the following years and thus ensure an increasingly denser shrub which has to be thinned out. In addition to deadwood and visibly diseased tissue (for example due to fungal infection), remove mainly older and thicker shoots from these shrubs or prune them down to lower, younger forks. Of the numerous thin, younger shoots, leave only about five to ten of the thickest remaining. After cutting, the shrub should generally appear more thinned out and at the same time should retain the natural appearance of its growth habit. A frequent mistake when cutting ornamental shrubs with soil-borne shoots is, for example, unnatural-looking oval-shaped or box-shaped topiary.
Ornamental shrubs without soil-borne shoots build up their twig structure through continuous branching. For this reason, its dense growth is only kept under control by thinning out: again, in addition to deadwood and visibly diseased tissue, only remove twigs which are growing inwards, crossing each other and scraping against each other. Prune shoots by cutting off the overlength at a suitable fork further in the direction of the base of the twig. In this way you can also shorten the shrubs overall: score the reference size at a suitable point (for example trim by 70 cm) and from this point shorten the shrub evenly all round by this length.
A frequent mistake when cutting ornamental shrubs without soil-borne shoots is just to “scythe them down” at any height. This leads to an unnatural “brush growth” appearance and makes these shrubs age and lose foliage from below.
Tip: Where ornamental shrubs become too large, you can replace them – depending on the type of plant – with slower growing varieties (for example forsythia with dwarf forsythia). This also requires the trimming, thinning cut, but the slower growing varieties do not reach an obtrusive size and much less is cut.