Pruning times of flowering shrubs
Shrubs offer structure in the garden in a way that smaller perennials cannot. Their bold forms and heavy foliage act as the skeleton of a planting plan which become increasingly obvious in the winter months. Although shrubs are primarily selected for their foliage and size they too flower.
Group 1: Spring flowering shrubs – bloom on growth formed last year Group 2: Summer flowering shrubs – bloom on current year’s growth Group 3: Flower on perennial spurs on older wood
Overview
Determine species to ensure pruning won’t reduce bloom.
If group 1-
Prune immediately after flowering
Remove DDD and congested or crossing stems.
Leave any new shoots as these will bear the following years flower.
If group 2-
Prune 20% back to ground level annually in early spring.
Flowered stems should be cut back to the first new shoots immediately after flowering.
Buddleia-
Cut back in early spring to 1/3 of its overall mass leaving just the initial thick woody branch network.
Any crossing or rubbing stems must be removed too along with any twiggy stems around the base.
Aim to leave a strong network of five to six main branches.
Hydrangea-
All Hydrangea flower on second year wood
Determine type of hydrangea
If mophead or lacecap-
Prune in the spring down to the first pair of healthy buds downwards from the previous bloom.
If foliage shows signs of damage prune to first healthy pair of buds
If climbing-
Prune immediately after flowering
Remove only overly-long shoots and dead wood.
Any frost damage should be cut back to next good buds.
Cornus-
Colour of stems fade as the stem ages.
Hard prune in spring, cutting back to approximately 10cm from the base in a coppice manner.
Note: young dogwoods should not be hard pruned, only coppice after full establishment at 4 years old
Lavender-
Spent flowerheads should be cut back to the height of the foliage.
In the spring the foliage should be taken a further 3cm.
Hard prunes in winter should go no further than the first set of stems from the base. Do not prune back right to thick woody base.
Winter/ early flowering-
Cut only DDD, crossing and congested stems after flowering in the spring.
To ensure a good bloom and a proper form it is important these shrubs are pruned correctly at the correct time of year. Many shrubs will only flower on 2 year old stems and some flower on 1 year old stems, it is therefore important to know whether to cut back fully every year (coppice) or to select old stems to remove in order to encourage replacement stems to bear flowers.
Although many shrubs are evergreen, some are deciduous (meaning they lose their leaves once annually).
Deciduous shrubs must be pruned in the winter only when leaves have fallen wheras evergreen shrubs often want pruning after flowering in summer months.
Flowering shrubs have been grouped into the following groups depending on their nature and subsequent pruning requirements
Group 1: Spring flowering shrubs – bloom on growth formed last year Group 2: Summer flowering shrubs – bloom on current year’s growth Group 3: Flower on perennial spurs on older wood
Common group 1 shrubs that flower on the previous years wood:
Witch hazel
Pieris
Quince
Viburnums
Azeleas and Rhododendrons
Lilac
Common group 2 shrubs that flower on new wood:
Buddleia
Elder
Spirea
Philadelphus
Weigelia
Forsythia
Ribes
Buddleia
Buddleia- cut back in early spring to 1/3 of its overall mass leaving just the initial branch network (see image). Cut through the thick woody stems, around 30cm above the ground, using a pair of loppers or a pruning saw. Make cuts just above a bud but don’t worry if none are visible as buddleia produces new shoots from below the bark.
Buddleia should be cut back hard in the winter leaving just the initial stump
Cut any dead, damaged, diseased wood making vertical cuts flush to the main stem. Any crossing or rubbing stems must be removed too along with any twiggy stems around the base.
Aim to leave a strong network of five to six main branches.
Hydrangea
Hydrangea- Hydrangea exists mostly in three distinct types, mopheads (the ‘regular’ globe shaped flowerhead with large petals), lacecap (these have tiny flowers in the centre of the bloom and an outer border of large petals) and climbing hydrangeas. Second year stems hold the flower of Hydrangea so pruning must be done properly.
Hydrangea pruning
Mophead and lacecap- these should be pruned in the spring down to the first pair of healthy buds downwards from the previous bloom.
On established plants, one or two of the oldest stems should be removed (3 years old stems only) to promote replacement growth.
If renovation is required cut all stems back to the base but beware this will not flower that summer as the second year wood bares flowers only.
Climbing hydrangeas- These should be pruned immediately after flowering in the summer, cutting back overly-long shoots and dead wood.
Heavy pruning will result in a flowerless season or two for the next couple years so should be done conservatively and in a 3-4 year staggered way.
Any spring frost damage should be cut back to the next good buds as well as the removal of any dead, damaged or diseased wood for all types of hydrangea.
Cornus (dogwood)
Cornus is planted as a winter interest shrub due to its bold coloured stems. However this characteristic requires proper pruning to maintain as the older shoots lose their vivid colour. It is important to only carry out such a prune once the plant has established fully after four years of growth.
In spring when the rest of the garden wakes up the drama of these stems become somewhat lost.
After the Cornus produces a fresh set of leaves in march is the best time to prune. This should involve a hard prune cutting back to approximately 10cm from the base (see image below).
Cornus ‘stools’
Lavender
Lavenders, need annual pruning to ensure an abundant bloom and a strong perfume.
lavender pruning
Firstly, after flowering when flowerheads have turned grey, the spent flowerheads should be cut back to the height of the foliage. In the spring the foliage should be taken a further 3cm (to encourage fresh shoots with a strong scent).
Lavenders will recover well from a hard cut back as light is allowed to reach the lower branches where fresh shoots can form. A hard regenerative cut back should go no further than the first tiny shoots found near to the woody base. New growth will not come from very woody stems so do ensure to leave the lower stems untouched.
Hard pruning of lavender
Evergreen shrubs
Evergreen shrubs generally require pruning in late spring in order to keep them compact and dense as well as ensuring a good bloom of flowers.
All evergreen shrubs should be pruned in spring with the overall aim to remove about a third of the overall wood mass. Like with any pruning, dead damaged and diseased (the 3 Ds) stems should be removed along with any crossing or overcrowded areas.
Small short lived shrubs such as lavenders and heathers flower on new wood meaning an annual prune will improve the coming seasons bloom whilst extending the life expectancy of the plant and preventing it from becoming overly woody.
Early or winter flowering shrubs such as Camellia, Berberis, Mahonia, Pieris and Rhododendrons should generally be left unpruned with the exception of removing and DDD or unsightly stems and deadheading. This if necessary should be undertaken in the spring.
Late flowering shrubs also require little pruning, just removal of DDD and deadheading whilst lightly pruning and undesired shoots that differ from the overall form after flowering in autumn.