Pruning Ornamental Shrubs in Your Garden
By Howard Drury
The Aims of Good Pruning
1. Remove dead, diseased, damaged, weak, and misplaced wood.
2. Improve the plant's shape and fully develop the characteristics for which it is grown, i.e. flowers, fruit, coloured bark, etc.
3. Increase vigour and rejuvenate by reducing the number of growing points and so increase the food supply to those remaining, if soil fertility is maintained.
4. Thin crowded growth to allow free air circulation and to let light into the centre of the bush to help the ripening of flowering wood and reduces pest and disease incidence.
5. Remove less desirable branch (es) where neighbouring branches are too close and liable to rub.
6. Remove growths not true to type, e.g. suckers, reverted parts of variegated plants.
General Points to Consider
All cuts should be made just above a bud, usually an outward facing one or a bud facing in the direction that growth is required in the future. All cuts should be clean. It is good practice to cut on the outside of any branch collars and tree paints are not normally used today. When removing branches the first cut is made a short distance from the trunk cutting upwards for a maximum of the girth of the branch. The second cut is just outside the first, cutting downwards. A third cut removes the stump close to the branch collar.
Pruning Groups of Ornamental Shrubs
Group 1 (Deciduous)
Plants flowering on current season's wood - Buddleia, Ceratostigma, Fuchsia, and bark effect shrubs. Cut the previous season's wood back hard to a few buds from the old wood, in March. Do this for flowering subjects after the required height has been reached, but for bark effect plants cut down hard the first spring after planting to build up a 'stool' effect.
Group 2 (Deciduous)
Plants flowering on previous season's growth e.g. Ribes, Philadelphus, Forsythia. Immediately after flowering prune some of the older flowered wood back to vigorous growth or as hard as space will dictate. Generally the harder that these are cut, the stronger the new shoots will be, providing the soil is fertile.
Group 3 (Deciduous & Evergreens)
Plants requiring little pruning e.g. Fothergilla, Hamamelis, Rhododendron. Generally pruning may be needed only to correct the Shape, perhaps if the shrub is becoming one-sided, overcrowded, or if dieback or disease has occurred.
Group 4 (Evergreens)
(a) Conifers and other evergreens
which may require trimming: Avoid cutting into old growth. Trimming may be done in summer but where removal of a large branch is necessary this should be done in Spring. When cutting out old growth, do it gradually over several years on one side of the hedge, leave for several years and then cut the other side.
(b) Grey foliage:
Most grey foliage plants e.g. Santolina, Senecio, Ruta can be pruned by this method. Cut back in spring as new growth appears by approximately two thirds to encourage new strong grey shoots and compact habit. Some foliage must be left on each stem to avoid complete die back. Cut Senecio hard back 1 year in every 3.
(c) Variegated
Aucuba japonica, Elaeagnus pungens and similar plants. Remove reverted shoots in variegated plants. Trim only if necessary in spring (for shape/size etc.). Any hard cutting should be carried out in April.
(d) Heathers:
Trim back with shears after flowering to remove seed heads and reduce size. Autumn and winter flowering varieties are trimmed just before growth starts (but before growth extends) in the following spring.
Group 5 (Climbers)
(i) Flowering on current season growth, e.g. Clematis Jackmanii group. Hard prune to framework in March.
(ii) Flowering on previous season's wood e.g. Jasminum, Wisteria, Ceanothus, spur back flowered shoots after flowering to one or two buds from the main branch framework. Remove also weak overcrowded growth.
Roses
Hybrid Tea
These should be pruned in February/March. Firstly remove shoots that are dead, diseased, damaged, old, weak, or growing into the centre. All remaining healthy shoots reduced by about two thirds, depending upon vigour. The harder you prune, the more vigorous the resultant shoots will be, providing that adequate food and water are available. Prune to an outward facing bud. Remove all unwanted shoots to ground level. Remove all suckers right back to the stock by digging down. To tidy up and reduce windrock, plants can be cut back to knee height in late autumn.
Floribunda
Generally pruned as for hybrid tea roses, but possibly leaving the strong healthy shoots a little taller.
Climbers
Shoots may be laid on the ground until new shoots appear, but usually cutting out some of the oldest growths to ground level each year provides sufficient vigorous growth from the base. All laterals on healthy main branches should be spurred back to three buds.
Ramblers
These should be pruned immediately after flowering. Remove all the long branches which have just finished flowering to leave sufficient space for the growth of the new shoots which are growing up from the base. If insufficient new shoots are growing from the base of the bush to replace the old flowering shoots, it will be necessary to leave the lower part of some of these older shoots, only cutting back to where a new vigorous shoot is growing out from it. Thin clusters of new shoots where necessary.
Plant Group Special Remarks
Amelanchier 2 Thin crowded branches in March
Andromeda 3
Aucuba 3 & 4c
Berberis 3 Thinning out or reshaping done after flowering or in winter after fruiting. Retain true shape of species.
Buddleia alternifolia 2
Buddleia davidii 1
Buxus 4a Retain natural shape
Callicarpa 2 Older and damaged wood may be cut out in spring.
Calluna 4d Spring prune winter flowering types, autumn prune summer types
Camellia 3 During April reduce straggling shoots.
Caryopteris 1
Ceanothus autumn fl. 1
Ceanothus spring fl. 5b
Ceratostigma 1
Chamaecyparis 4a Cut back to living wood.
Chaenomeles 5b When trained as a wall shrub
Choisya 2
Clematis alpina 5b Prune spring flowering varieties in early summer after flowering to reduce old wood.
Clematis florida 5a rune older shoots in Feb. to 1m. above ground where space is limited.
Clematis tangutica 5a as above.
Clematis jackmanii 5a Prune to within 0.3m above ground in (Large Flowered Hybrids) in February before growth commences.
Clerodendrum 2
Cornus (bark effect) 1 May be done on 2 or 3 year cycle.
Cornus (tree type) 3 Cornus Mas etc.
Corylopsis 3
Corylus 3
Cotoneaster 3 or 5b Responds well to hard pruning if necessary.
Cupressus 4a Retain a leader if possible.
Cytisus 2
Daboecia 4d In Spring as active growth commences.
Daphne 3 Only prune if really necessary.
Deutzia 2 Other stool habit ‑ remove older branches.
Elaeagnus pungens
(variegated) 4c
Elaeagnus ebbingei 3
Erica 4d
Escallonia 3 After flowering if required.
Euonymus 3 Variegated forms as 4c.
Forsythia 2
Fothergilla 3
Fuchsia 1 In spring or treat as Group 2 in mild areas, to allow for increased size of bush. See Fact Sheet 49.
Garrya 3
Gaultheria 3
Griselinia 3 Variegated form as 4c or informal hedge 4a.
Hamamelis 3
Hebe 3 ,4c,4b Depending on cultivar.
Hedera 4a,4c
Helichrysum 1 or 4b In case of frost damage.
Hibiscus 3
Hydrangea paniculata 1 In February/March.
H. petiolaris 5 Remove only dead, weak or misplaced unwanted growth.
Hypericum 1 Could be pruned every other year.
Ilex 3 or 4a If shaping required. 4c if variegated. July/August.
Jasminum 5b
Kerria 2
Kolkwitzia 2 Old, weak growth removed after flowering in July.
Ligustrum 4a Trim with shears after flowering or clip as required if grown as hedge.
Lavendula 4a Trim in spring after growth commences.
Leycesteria 2 Prune older branches hard back to base or new vigorous shoot near base.
Lonicera fragrantissima 5b Prune back laterals after flowering (wall trained)
Lonicera japonica
(climber) 5a May be clipped over with shears in spring.
Lonicera periclymenum 5b Prune out portions after flowering as necessary.
Lonicera nitida (shrubby) 3 Occasional hard pruning to 150mm improves vigour & base of plant.
Lonicera pileata 3
Magnolia 3 Cuts heal slowly best left alone. Otherwise prune in July.
Mahonia 3 M.aquifolium occasionally cut down to 100‑200mm in April. Otherwise treat all as Group 3.
Olearia 3 But responds to heavy pruning if necessary.
Osmanthus 3 As for Olearia.
Pachysandra 3 As for Olearia but in May.
Parrotia 3 Do not thin crown.
Pernettya 3
Philadelphus 2 Annually after flowering.
Phlomis 3 Prune back dead wood to encourage new growth from base in spring.
Pieris 3 Prune out winter damage in May.
Piptanthus 3 If caught by frost trim to healthy wood in spring and remove old shoots.
Pittosporum 3 Liable to frost damage. Examine in spring and remove dead wood if any killed.
Potentilla 3 Old, weak, smaller growths in spring if necessary.
Prunus 4 Best trimmed formally or laurocerasus informally with secateurs. Responds to hard pruning in spring/early summer.
Pyracantha 3 or 5 If trained against wall, cut back outward spur after flowering.
Rhododendron 3 Remove faded flowers. Cut hard in April if bushes become straggly. Dead wood as required. Some respond to hard pruning.
Rhus 3 or 1 If grown for bark effect.
Ribes 2 Shoots from base.
Rosa species 2 Cut out older growths at base. Shorten any of previous year's wood remaining.
Rosmarinus 2 or 4a Trim to shape in spring or light pruning after flowering
Rubus 1 To allow bush to increase in height where required treat as group 2, but never allow wood older than 2 years to remain except for bark effect.
Ruta 4b Cut hard back every other year with shears.
Salix 1,2,or 3 Treat as Group 2 if greater size required but never allowing wood older than 2 years to remain unless being grown as a tree.
Salvia 4b Prune in spring.
Sambucus 1 Or as Group 2 if larger bush required.
Santolina 4b Prune in spring.
Senecio 4b Best pruned in spring.
Skimmia 3 Prune only if necessary in spring.
Spiraea x arguta 2 Prune after flowering usually in spring.
S. thunbergii 2 " " " " " "
Spiraea x bumalda 1 Cut back hard in spring to 150mm if required.
S. japonica 1 Cut hard back in spring if required.
Symphoricarpus 2 or 3 Often difficult to prune large clumps. Best left.
Syringa 3 Dead‑heading is desirable, major pruning during winter if necessary.
Tamarix autumn flowering 1 Prune to 75‑100mm of old growth in spring.
Tamarix spring flowering 2 Thin and shorten back after flowering.
Taxus 3 or 4 Major pruning in May, otherwise trim in summer.
Ulex 3 Prune lightly in summer. Every 2‑3 years harder pruning in March.
Viburnum 3
Vinca 1 Cut with shears in April. Remove weeds etc.
Weigela 2 Prune after flowering in July.
Wisteria 5b Shorten laterals to 150 mm in summer. Further reduce to 2 buds in December/January.
The information given in this Fact Sheet is provided in good faith. It is however of necessity general information and advice on the topic. Howard Drury will not be under any liability in respect of the provision of such advice and information, and you are strongly advised to seek independent advice on any particular gardening problems or queries you may have, preferably from experts who can (when appropriate) inspect the problem before providing advice.
© 2022 Howard Drury This material has been produced by Howard Drury and must not be reproduced in part or full without the written consent of Howard Drury, Kings Heath, Birmingham, B13 0SJ.
JHD/25/03/2022