Reasons for pruning:
1. Remove any dead and diseased wood for the health of the plants. Do this before attempting any other pruning as this may alter the shape of the plant.
2. Improve the shape, either to form the outline or open a bush to let in light and air. The increased light and air improves the health of the plant. Pruning for shape is a good idea in the early years of a plant’s life.
3. Increase the number of flowers or the quality of those flowers. Hydrangeas are best pruned in winter, at the very end of the winter or early spring being our area is prone to late frost.
Hydrangea Varieties: Hydrangea arborescence ‘Annabelle’ Hydrangea macrophylla ‘Pink Elf’, ‘All Summer Beauty’, ‘Buttons ‘n Bows’, ‘Endless Summer’, ‘Forever Pink’, ‘Varigata’, ‘Nikko Blue’, ‘Big Daddy’ Hydrangea quercifolia ‘Oakleaf’ Hydrangea serrate ‘Bluebird’, ‘Preziosa’ Hydrangea panciulata ‘Grandiflora’, ‘Kyushu’, ‘Limelight’, ‘Pink Diamond’, ‘Tardiva’, ‘Unique’, ‘White Moth’, ‘Angel’s Bush’
Pruning for Different Variety Types:
Hydrangea arborescence: apart from an occasional tidy-up, they don’t need pruning. Although they can be pruned drastically to increase the size of the flowers, one method is to cut all branches to one foot from the ground in the winter.
Hydrangea macrophylla: On a large established shrub, thin shrub out by taking out 2-3 large stems, down close to the base of the plant. This has the effect of thinning the shrub and reduces overcrowding. The plant will have fewer but bigger flowers next year, as there is less competition. Do this thinning every year in late winter or spring. If you want to keep your plant at a reasonable height and have a good display of flowers every summer, you can prune lightly overall instead of just removing the dead flower heads.
Look for the large buds which are next summer’s flowers. The buds are usually in opposite pairs near the tops of the stems. You need to retain as many of the fat flower buds as is practical for the shrub to flower well. Thin the stems, at the same time as removing the weaker growth. Then reduce the height of the remaining stems, at the same time remembers to preserve enough flower buds.
Another method of pruning that will increase the individual size of the blooms which will be at the expense of overall display (the bush will have fewer flowers but each will be larger). First remove all thick and spindly growth, cutting these out as low as you can go. You are now left with good thick stems. Hold each stem in one hand and go down the stem until you find the lowest set of big buds (the big buds are the buds that contain the flower head in miniature), can cut above the lowest set of large buds. This will give you 1 or 2 huge flower heads instead of 6 or 8 smaller ones.
Hydrangea quercifolia: it’s a good idea to remove the spent flower heads on oakleafs, but generally these don’t need to be pruned except for shaping the plant.
Hydrangea serrate and Hydrangea macrophylla: are pruned regularly, but will not suffer if left unpruned. Young plants that were recently planted should be left unpruned for the first couple of years, or just lightly pruned to make a good shape. Timing is important when pruning an established shrub, especially since our area is prone to late frosts. Wait until the end of winter or early spring before pruning and removing spent flower heads.
Hydrangea panciulata: types can be left unpruned, which would be best for ‘Kyushu’, ‘Unique’, ‘White Moth’, ‘Pink Diamond’, ‘Tardiva’, and ‘Angel’s Bush’. It is recommended to prune these only to maintain their size. Now with the ‘Grandiflora’ and ‘Limelight’ it is best to prune these hard to encourage the spectacular giant blooms. To do this, cut the previous summer’s growth back really hard to one or two buds.