Cut after flowering
Many spring-flowering shrubs form their flower buds in the previous summer and overwinter them. After flowering, they develop new shoots, on which they form more flower buds for the following year. Pruning before flowering would remove most of the flowers. Such shrubs are therefore pruned after flowering. However, since shoot growth begins after flowering, you shouldn't wait too long to prune, or you'll remove the new growth.
This group includes shrubs that flower on annual long shoots. These are typical early bloomers such as spirea and almond trees. The most beautiful flowering wood is found on annual shoots that are longer than 30 cm. Without pruning, only short shoots develop, which will flower, but the old branches become bare and impair the visual appeal. Pruning removes old shoots and promotes many new flowering long shoots.
This group also includes shrubs that flower on one-year-old side shoots, such as forsythia. In mild climates, they bloom on one-year-old long shoots. They only develop their full beauty when they have formed side shoots on the long shoots in the second year. From the third year onwards, the shoots age very quickly and hardly flower anymore. Here, too, pruning promotes the formation of young, vital shoots. Shrubs that flower on older shoots and short shoots are also pruned after flowering. These woody plants develop long-lasting flowering wood. They generally do not form flowers on one-year-old long shoots. Only the two-year-old long shoots form side shoots with flower buds – as in the previous group. The shoots do not age, however; the flowers appear on older shoots several years later. This group includes serviceberry and witch hazel. They are not pruned every year, but only rarely.
Rejuvenate ornamental trees
If ornamental shrubs become too large with age and the shoots become senescent, one or more shoots should be replaced with a rejuvenation pruning to maintain flowering. After pruning a shoot, new shoots will emerge at the cut site. One of these shoots will take the place of the removed branch after a few years.
When rejuvenating ungrafted shrubs, the new shoots must emerge directly from the ground—these are so-called ground shoots. If, however, you leave a stump when cutting back the old shoots, this will quickly produce new shoots from the old wood, which will quickly become aging.
In grafted woody plants, the ground shoots correspond to wild shoots, which are unsuitable for rejuvenation. Therefore, they are rejuvenated close to the ground, but always above the grafting point.
Leave the cone standing
With some ornamental shrubs, small cones are left behind when branches are removed. These prevent the wood from drying out into the trunk. These cones also contain buds from which new shoots emerge, serving as replacements for removed shoots. If these cones later partially dry out, they are removed the following summer.
