Aucuba

The spotted laurel, aucuba japonica, is the species most widely grown.

 

Despite its name the species itself has plain foliage; only its varieties have spotted or variegated leaves.

 

No routine pruning is required, but if the shrub begins to outgrow its space trim it back in mid-spring (Technique B).  If grown as a hedge, trim in mid- or late summer.  RHS: non-fruiting plants may be pruned in winter. 

 

Use secateurs not shears, otherwise the cut leaves with turn brown and look unsightly.

 

After planting: To help create a good shape, shorten all the previous year’s growth by about one-third, between early and late spring.  If planting at any other time, wait until the following spring before planting.

 

Brachyglottis

Evergreen, usually mound-forming, mostly hardy shrubs, formerly classified under Senecio; most have attractive silvery-grey foliage and bear terminal clusters of daisy-like, yellow flowerheads on the previous season’s growth in summer.  Hard pruning results in a finer foliage effect, but will be at the expense of the flowers.  Most prefer a sunny aspect but tolerate windy coastal conditions.  In shady or damp sites, however, they may become leggy.  In cool climates plants are often damaged by frost, and a heavy fall of show can break the rather brittle branches.

 

Prune in mid-spring, when any danger of severe frost has passed and with the onset of new growth.

 

Established plants may also be clipped to shape after flowering.  Prune hard to renovate damaged plants, cutting back to active buds on older wood.  Plants must be in good health for renovation to be successful; old plants are best replaced.

 

They benefit from regular pruning, though not necessarily annually, to stimulate plenty of attractive foliage rather than flowers and to maintain compact plants.  Cut back the stems to within 5-10 cm of the ground in spring as soon as shoots can be seen growing from near the base.  This drastic treatment is only likely to be successful with plants pruned hard annually from an early age.  If there are no new shoots near the base, cut the previous year’s shoots back to 5-10 cm of a taller framework of old wood. 

 

A neglected plant or one that has been damaged during a harsh winter, can sometimes to rejuvenated by cutting back very hard.  To do this, prune to within 5-10 cm of the ground in spring, then water and feed well.  The plant will then probably recover.

Buddleia 

Butterfly bush

Some of the most popular buddleias should be pruned hard each spring to keep them compact and encourage large flowers.  Others are best pruned moderately in summer.  The most widely grown buddleia is the common butterfly bush, B. davidii.  It is typical of those that flower at the ends of the shoots produced in the current year.  Prune it annually otherwise it will become leggy with the flowers at the ends of tall stems.  In a small garden buddleias are best cut back close to the ground each spring using Technique E.

 

In an exposed position cut about a third off each stem in late autumn to reduce wind damage in the winter.  Finish the pruning in mid spring by thinning congested and old framework stems and cutting out any that are producing badly positioned growth.  Cut back all the remaining stems to within 2 or 3 pairs of healthy buds of the woody framework.  [I always say to cut back to 45 cm high.]

 

After planting: In spring cut back b. davidii to within 5 cm of the old wood.  If planting at other times, wait until the following spring before pruning.

 

Ceanothus

Californian lilac

 

Both deciduous and evergreen species and hybrids are grown for their haze of blue flowers, but the method of pruning differs.

 

Deciduous ceanothus: Cut back all the branches in spring as the leaves begin to appear to about 7.5-10 cm from the point of origin of the previous year’s growth (Technique E).  Without regular pruning the shoots become weak and flowering performance poor.

 

Evergreen ceanothus: Routine pruning is not essential for evergreen species but to encourage new growth it is worth cutting 2/3rds off each new shoot after flowering (Technique C).  Evergreen ceanothus are often grown against a wall for protection.  Secure the branches to a strong trellis or training wires, and tie in new shoots in early summer and again in early autumn.  If they become bare at the base, try planting another shrub in front to disguise the unattractive plant.  Evergreen ceanothus are sometimes damaged in a cold winter and in unfavourable areas they may even be killed.  If severely damaged cut back to healthy living wood to stimulate new growth from the base.

 

C. thyrsiflorus pruned midsummer after flowering.  Cut back longer flowered shoots by one-third to a half.  For more bushy growth, trim them again lightly later in summer.  For training as a wall shrub, tie the plant in starting with main stems and well-placed laterals.  Pinch out the tips of young forward-growing shoots to encourage sideways branching.  Shorten the longest laterals by a few buds, particularly where growth is gappy to stimulate branching and balanced coverage.  Once established, tie in new growth, shorten weak shoots, prune flowered growth (removing some completely where there is congestion), shorten stems where the shrub is reaching the limits of its allotted space, and check any ties that are broken on constricting growth.

 

Choisya

Mexican orange blossom

 

Choisya require no regular pruning but it may be necessary to remove winter damage.  Although hardy in most areas, in a position exposed to severe wind-chill the glossy evergreen foliage may suffer.  Remove entirely any badly frost-damaged shoots in early spring to encourage new growth from the base.  If it is only the leaves at the end of the shoots that are affected, cut back to healthy foliage.  Although not essential, you can keep the foliage looking young and fresh on a mature shrub by cutting back 1/3rd of the oldest branches close to the ground after flowering (Technique D).  This will encourage new shoots from the base. 

 

Pruning back flowered shoots will encourage a second, smaller flush of flowers.

 

Autumn flowers: Choisya ternata bears fragrant white flowers in spring but it will often continue to bloom intermittently throughout the summer until autumn.  You can encourage autumn flowers by cutting back shoots that have flowered by about 25-30 cms as soon as the spring-flowering is over. 

 

Clematis

 

Clematis are relatively simple to prune once you have discovered which group they belong to.

 

GROUP 1 (including macropetala)

These flower in spring and early summer on shoots produced the previous year and generally have large numbers of relatively small flowers. 

 

When to prune: prune after flowering but only if necessary.  Do not prune in the winter, otherwise you will cut off the shoots and lose the new season’s flowers.

 

How to prune: regular pruning is usually unnecessary especially if the plant is growing into a tree or other some other natural support.  A plant growing along a fence or one that has become too large for its support should have dead wood and surplus growth removed after flowering to keep the plant within its allotted space.  Do not worry about cutting back to a particular point; just remove enough growth to confine the plant. 

 

GROUP 3 (including durandii)

These flower in late summer and autumn, on shoots produced in the current year.  They tend to become bare at the base if not pruned regularly. 

 

When to prune: prune in the late winter or early spring.

 

How to prune: Cut the plant back to the lowest pair of plump, health-looking buds you can find.  These will be about 30-90cm above the ground.  This may mean cutting off green healthy shoots but the plant will re-shoot from the base and be better for it.

 

Cornus

Dogwood

 

This large group of plants includes shrubs and trees that require very different pruning techniques.  Those grown for their coloured stems should be pruned regularly.

 

For coloured winter stems cornus alba should be pruned by cutting back hard to a stubby framework of stems in spring before bud break using Technique F.

 

After planting: cut back cornus alba varieties, whether grown for foliage or stems to within 5 cm of old wood in spring.  If planting at any other time of year, it is best to wait until the following spring before cutting back.

 

For ornamental foliage: some shrubby dogwoods have attractively variegated foliage.  These are best pruned to encourage large leaves even if they also have coloured stems. Cut out one stem in three or four (Technique D) in mid-spring.

 

Corylus

Hazels, Filberts

Corylus avellana “contorta” with corkscrew-like branches.  Once it has reached a reasonable size (when it is about 5 years old), cut out 1 stems in 3 (Technique D) in mid-spring.  Repeat this every second or third year, but not annually.

 

Cotoneaster

This large group of plants includes both evergreen and deciduous species that range from ground-huggers to large shrubs of almost tree-like proportions.  Few need routine pruning, and this to limit size.

 

Cut out one stem in 3 each year (Technique D) once they have filled their allotted space.

 

Prune deciduous species in late winter or spring before the leaves open, evergreens in mid-spring.  Most cotoneasters reshoot even if cut back hard into old wood, though this is not normally necessary.  Take care not to spoil the natural shape of the plant by heavy pruning. 

 

C. horizontalis: prune late winter, removing congested, old and sparsely furnished growth by cutting right back to the main stem.

 

Euonymus

Euonymus vary from ground-hugging evergreens to small deciduous trees or large shrubs, but no regular pruning is required. 

 

Variegated varieties of the evergreen E. fortunei such as “Emerald ‘n’ Gold” are widely planted as ground cover.  They also look good as individual shrubs at the front of a border, and if planted at the base of a wall the shoots will grow upwards, instead of horizontally along the ground.

 

No routine pruning is required, but if you want to encourage denser ground cover cut back the previous year’s growth in early spring.  However, this should only be done once or twice, and is not an annual job once the plants are well established.  If old plants begin to look neglected, cut out 1 stem in 3 (Technique D) in early spring.

 

After planting: evergreen euonymus need all the previous year’s growth shortened by about one-third after planting in spring.  If planting at any other time, wait until the following spring before pruning.

 

Fatsia

False castor oil plant

Fatsia japonica requires little pruning, but if it grows too large for its allotted space remove the oldest stems at ground level in spring.  You can keep the shrub compact and ensure that it produces plenty of attractive yougn leaves but cutting out one stem in three in mid-spring each year (Technique D); generally it shoots readily from old wood.  A balanced shape is important to the appearance of fatsia japonica, so cut back any shoots that seem to be spoiling the outline in mid-spring.  It is best to remove any gaunt or unwanted branches completely; shortening them spoils the plant’s naturally graceful habit, and the fresh growth will break freely from the base.

 

Ficus

Fig

In mild areas f. carica can be grown as a very decorative shrub with large, attractive leaves.

 

If given the space it will make a spreading shrub but you can restrict its size if you need to by pruning back all of the over-large shoots.  Take them back far enough to hide the cut end from view.

 

If it becomes really overgrown and untidy, try cutting it back hard to just above ground level in spring.  You may find that nature does this job for you, killing the top growth during the winter.

 

Fortunately the fig has great powers of rejuvenation and new growth normally regrows easily even after such drastic treatment.

 

Vigour can also be restricted by planting where the roots can be confined (in an area of paving, insert slabs or other barrier vertically into the soil to limit the horizontal spread of the roots, or by root pruning where this is practical).

 

Fuchsia

In all but the mildest climates the top growth will be killed in the winter, and pruning consists of cutting back the old or dead stems to ground level (Technique A) in mid- or late spring once growth commences.  Despite this apparently drastic pruning new shoots will appear in profusion. 

 

Fuchsias shoot freely from old wood and flower on shoots produced in the current year, so they are very tolerant of hard pruning if necessary.

 

Shorten stems by one-third in autumn to reduce the risk of wind damage in cold, exposed sites.

 

Hebe

Shrubby veronica

Most hebes have very compact mound-forming or carpeting growth and for these routine pruning is unnecessary.

 

Many hebes are of borderline hardiness and may be damaged during a severe winter: the leaves will become brown and the stems bare.  Do not be tempted to prune these damaged shoots until spring, for they may afford the plant a little extra protection.  Wait until the new growth appears, then it will be clear how much of the dead or damaged shoots will have to be cut off.  Start by pruning back to the first strong new bud developing on each shoot, but be prepared to cut back further about a month later to produce a better-shaped bush.

 

If the shrubs become leggy, prune back hard in mid-spring.  Fortunately hebes will usually shoot from old wood, whether hard pruned or cut down by frost, and sometimes they grow new leaves along bare stems.  The appearance of hebes will be improved if you pick off the dead flowers or developing fruites.

Jasminum

Jasmine

Most of the hardy jasmines are climbers, but one of the most popular, the winter jasmine, J. nudiflorum, is more of a sprawly shurb with long flexible stems that benefit from the support of a wall or trellis.  To encourage more flowers, cut out one stem in three (Technique D) in mid-spring as soon as flowering is over.  All need pruning to prevent a build-up of old wood. 

 

Juniperus

Juniper

Junipers range from large trees to dwarf, ground-hugging shrubs.  They require no routine pruning. 

 

Conifers generally:  They usually have several main shoots instead of just one dominant one.  You do not need to reduce any of these multiple shoots.  If prostrate conifers produce upright shoots, remove these at their point of origin.  Conifers do not grow well from old wood.  If you cut back into mature wood new shoots will rarely develop and you will be left with bare stubs.  Therefore only cut conifers back to live, visible buds.  Cut off damaged and misplaced branches completely rather than leave a stub.

Laurus

Bay, bay laurel, sweet bay

The species most often grown is bay laurel, Laurus nobilis, used as a flavouring in cooking.  It can be left unpruned or clipped or cut back hard to shape the bush (Technique B) in mid-spring.  Use secateurs rather than shears as these can slash the leaves causing them to turn brown.

 

Trim small mop-headed or trained trees twice a year, in mid-spring and again in mid- or late summer, rather than pruning them more severely once a year.

 

In most areas, young bays are particularly susceptible to weather damage.  Cold winds will cause the leaves to turn brown at the tips.  The plants will usually outgrow this damage as new growth appears, but the scorched leaves are unsightly so try to prune most of them out of a formally clipped specimen in spring.

 

Occasionally, shoots may be killed in a very severe winter, even on a mature plant.  If this happens, cut back to live wood once you can see where new shoots are appearing, or cut back the whole bush to about 30 cm above the ground.  It will normally re-grow, but the new shoots will take several years to reach a respectable height.  This technique should be tried only on a badly damaged or very large old plant that you would otherwise remove altogether.

 

Lavandula (see also entry under perennials)

Lavender

Lavenders respond well to routine pruning.  To improve their overall appearance, cut back the previous year’s growth to new shoots within 5-10 cm of the ground in early or mid-spring (Technique G) just as new growth starts.

 

If you want a larger plant, cut to within 5-10 cm of a framework of old wood.  This severe pruning is only suitable for lavenders that have been pruned annually in this way from a young age.  On old plants that have not been pruned hard regularly, just shorten the previous year’s growth in spring.

 

If you have a lot of plants clip them lightly with shears after flowering.  This will also remove the dead heads which look unsightly if left on over winter.  Prune lavenders used for a low, informal hedge in the same way.

 

Unfortunately, lavenders have a relatively short useful life, and even with regular pruning may start to sprawl and die back in time.  Therefore it is worth taking cutting in summer to replace plants that cannot be improved by pruning.

 

Lonicera

Honeysuckle

Honeysuckles are a diverse group of plants.  Most are climbers, some are busy, and one, L. nitida, is widely used as a hedging plant.

 

Climbing honeysuckles don’t need pruning but can be cut back if they become tangled or too large.  They fall into two groups and it is important to determine which group your honeysuckle belongs to.

 

Those that have their flowers in pairs on the current year’s growth, of which the Japanese honeysuckle, L. japonica, is the best known, can be pruned drastically if necessary.  If they outgrow their allotted space, just clip them to size with shears during the dormant season, mid-winter to early spring, or after flowering.

 

The climbers that produce blooms at the end of the shoots in whorls (radiating like the spokes of a wheel), or in clusters, flower on stems that are at least a year old.  The majority of climbing honeysuckles, including the popular woodbine, L. periclymenum, fall into this group.  Prune them as soon as flowering is over by cutting back each flowered shoot to a point where there is a non-flowering young shoot to replace it.  This is often difficult because old and young stems usually twine around each other, and it is usually impractical to cut back all the flowered shoots.

 

Overgrown climbers - over the years, the stems of climbing honeysuckles become so entwine that pruning is difficult.  If the plant simply needs containing, prune all stems back to their support or cut off the highest growth if this has started to cascade down in a curtain of tangled woody shoots.  You will sacrifice flowers for a year (unless the species is one such as L. japonica), but this treatment will improve the plant’s appearance in the long run.

 

If the plant is climbing over a trellis that needs repair or maintenance and the plant is so well established that it is impractical to untwine the stems, cut the whole plant down in the autumn to about 5-10 cm above the ground.  If the stems are very tangled, cut them in several places along their lengths and at the base.  Leave for a week or two to allow time for the foliage to die and then disentangle the wilted sections.

 

Vigorous new shoots will grow the following spring and these can be trained in from scratch.  You will lose flowers for a year, but the benefits of maintaining the support and making the plant more tidy will make the loss worthwhile.

 

Perovskia

 

The shoots of Russian sage, P. atriplicifolia, are usually killed back to within a few inches of the base in winter weather, but new shoots grow readily in spring. 

 

In mid-spring, just as new growth is beginning, cut back the previous year’s shoots to within about two buds of the base.  Usually this will be about 5-10 cm above the soil. 

 

Do not remove the old stems before spring, even though the plants would look tidier, as they may provide the plant with a little extra protection during the winter.

 

Philadelphus

Mock orange

Most philadelphus increase in spread quite rapidly which, coupled with the height of some, makes regular pruning desirable.  Timing is important, however, as they flower on wood produced in the previous year.

 

Cut out one stem in three (Technique D) in mid-summer, after flowering.  This will encourage a constant supply of new shoots that will flower well on compact plants.

 

Always bear in mind, however, that the natural height varies widely from one species or variety to another.

 

P microphyllus has a natural height of 60-90 cm.

 

Regular pruning will improve the overall shape and compactness, but it will not restrict the height of a naturally tall variety.

 

Physocarpus

Ninebark

The species usually grown is P. opulifolius, and this shrub produces young shoots from ground level among the older stems which have peeling bark.  Regular pruning will encourage plenty of attractive mahogany-brown new shoots for winter interest.  Cut out one stem in three (Technique D) in mid-spring.  RHS: remove up to 1 in 4 of the oldest stems in summer after flowering.

 

Pittosporum

Pittosporums are naturally neat in appearance.  They are usually reliably hardy in mild areas, but may be damaged or killed in a very severe winter.  In cold areas provide winter protection or else be prepared for winter damage and probably losses.

 

If most or all of the shoots are killed, do not dig the plant up until you have given it a chance to show signs of growth.  Cut the plant back close to the ground and it will often produce new shoots.  Within a year or two it may be as attractive as before. 

 

Fortunately the popular P. tenuifolium and its varieties will usually grow readily from old wood and damaged shoots can be cut out with confidence.

 

Pittosporums need no other regular pruning, but if you want a neatly shaped shrub clip with shears (technique B) in late spring.  If untrimmed plants become straggly in time, shorten long shoots in mid- or late spring to improve the shape.

 

Potentilla

Shrubby potentilla, shrubby cinquefoil

The many varieties of the shrubby potentilla, p. fruticosa, need regular pruning to keep them in good shape and flowering well.  Cut out one stem in three (Technique D) in early spring.  This method of pruning will prevent growth becoming congested with old and weak branches that spoil the look of these hardy shrubs.

 

If you have a very old neglected plant that is flowering poorly and looks untidy, rather than dig it up try cutting it back hard to within 15 cm of the ground.  Remove some of the new shoots to form a bush of neat and manageable proportions.  Prune normally (using Technique D) in all subsequent years. 

 

Prunus

This genus includes many ornamental trees and shrubs as well as fruits such as cherries and plums.  Few ornamental prunus require pruning, but the main exceptions are detailed here.

 

Laurels are tough shrubs that tolerate hard pruning if necessary.  No routine pruning is required if the plant is growing in a border, but cut back as hard as necessary, preferably in late winter, if it begins to outgrow its allotted space.  Do not be afraid to cut into old wood.  An overgrown laurel will grow new shoots quite easily if you cut it down to about 15-30 cm from the ground.  Hedges are generally trimmed in late summer.

 

Silver leaf disease, chondrostereum purpureum, is a particular problem for prunus.  It enters through wounds, generally between early autumn and late spring, so avoid pruning during this period.  Whatever the time of year, it is worth using a wound paint on large wounds.

 

If pruning branches that are already affected by the disease, cut back beyond the limit of the tell-tale brown stain that is visible in the wood.

 

Pyracantha

Firethorn

Pyracanthas grown as free-standing shrubs require little in the way of pruning, but cut them back hard in late winter if it is necessary to improve the shape or control size.  Try to cut back the shoots to points close to the centre of the plant so that the pruned branches are inconspicuous.

 

Wall-trained plants must be pruned annually.  If you simply want to keep the plant tidy, a clip over with shears in late winter is generally sufficient and will produce a flat, hedge-like finish.  If thick or particularly long shoots grow out, cut these back with secateurs to a point well within the plant.  For a good show of berries on a more formally trained plant, use the technique described below.

 

For the first 2 or 3 years concentrate on training the shoots to the wall.  They are largely self-supporting in time, but tie them to horizontal or vertical wires fixed to the wall for early support.  You can train them as formal fans or espaliers, or adopt a less rigid approach with branches that snake randomly up the wall.

 

Once the framework branches have been established, shorten all new sideshoots in mid-summer so that only 2 or 3 leaves remain.  This will expose the berries to view and encourage more flower buds to develop the following year.

 

Rhododendron

Rhodoendrons including evergreen and deciduous azaleas will benefit from pruning once they are fully grown (usually after 10 to 15 years), although this is not essential.  If at that stage you cut out one stem in three annually (Technique D) in mid-summer, a regular supply of new growth and more flowers will be encouraged.  This should not be necessary for dwarf rhododendrons and azaleas.

 

Deadheading is beneficial, especially on young plants, as it prevents the plant putting energy into seed production.  Snap off the dead flowers by hand each year, but be careful not to damage the developing bud behind.

 

To rejuvenate an old bush, cut the whole shrub back to 30 cm above the ground in early spring.  It may be several months before the stubs produce new shoots.  These will not grow much in the first year, but will usually grow vigorously from the following year.

 

 

Rosa

Rose

Florabunda roses produced better-quality flowers in trials when roughly pruned with secateurs or with a hedgetrimmer, rather than carefully pruned with secateurs.  The blooms of large flowered (hybrid tea) varieties were equally good with either method. 

 

Rose pruning can usually be done whenever it is convenient, between autumn and when the leaves emerge in spring.

 

If you prune in the autumn, diseased shoots and shoots from the base (which may be below the graft, from the rootstock, so should be removed) are easier to recognise and less diseased material is likely to be carried over the winter, wind is less likely to cause damage (wind rock), and the beds look neater if you underplant with bulbs and spring bedding plants. 

 

If you wait until spring, the danger of frost damage is reduced.

 

Rosmarinus

Rosemary

Most rosemaries (varieties of R. officinalis) need regular pruning so that they do not become woody and unattractive.

 

To encourage compact plants with plenty of young foliage, cut back the previous year’s growth to within 5-10 cm of the ground (Technique G) as new growth begins in spring, on the other hand if you want large plants cut back to within 5-10 cm of a taller framework of old woody stems which will give you the required height.

 

Old, neglected specimens will usually develop fresh growth if cut back severely.  But as rosemary is easy to propagate from cuttings taken in summer, it is best to start again with a new plant that you can prune regularly from an early stage.

 

Rubus

Treatment varies depending on type.  No idea what type ours is.

 

Salvia

Shrubby salvias benefit from regular pruning.  Sage, s. officinalis, is the species usually grown, generally in one of its variegated or purple-leaved varieties.  It makes an attractive plant when young, but unless pruned regularly will become straggly with bare patches with age.

 

To encourage dense and healthy foliage, cut back all the stems to within 5-10 cm of the ground once you can see new shoots beginning to grow from near the base in spring when growth begins.  Old plants may not respond well to this treatment if they have not been pruned routinely, but they can be cut back to within 5-10 cm of a larger framework of old shoots to make them more compact.

 

Spirea

Spiraeas vary in the way they grow and flower.

 

Spring-flowering species bloom on old branches and include bridal wreath s. x arguta.  Cut out one stem in 3 (Technique D) after flowering, i.e. early summer.

 

Symphoricarpus

Snowberry

Most of these hardy shrubs bear white berries which remain on the plant for several months.  To encourage the growth of new shoots, cut out one stem in 3 in mid-summer (Technique D).

 

Some species such as s. albus eventually form thickets and it is difficult to restrict their spread.  Rather than attempt to control by pruning, plant them where there is a natural constraint to their spread, such as a concrete path.

 

Snowberries are often grown as informal hedges.

 

If a snowberry is neglected it can become an impenetrable mass of stems that are difficult to prune.  Try cutting back to just above the ground in spring.  New shoots will usually be produced that will be easier to prune routinely in future, but if the clump is very large it may be best to dig it up and replant some smaller pieces.

 

Syringa

Lilac

Lilacs benefit from routine pruning.  Although some of the species have a naturally low, bushy habit, the popular s. vulgaris varieties grow tall and leggy if pruning is neglected, and they also need sufficient space and light for the shrub to develop without competition from other plants.

 

To maintain an attractive overall appearance, cut out very old or very weak stems in winter.  Aim to remove about 1/4 of the old or weak stems each year on mature plants.

 

Careful deadheading will improve flowering the following year.  As soon as flowering is over/fading in mid-summer, cut the dead blooms back to the first pair of leaves below the flower head.  Do not cut back further or you risk remove the buds from which the new flowering shoots will be produced.

 

In time lilacs, especially s. vulgaris, become very large (we should be so lucky).  These old, neglected plants can often be rejuvenated by sawing the plant down to stumps 30-90 cm high.  New growth will be produced even from this old wood, but do not expect a good show of flowers for 2-3 years.

 

Viburnum

Many viburnums benefit from periodic pruning to stimulate new growth and to prevent the shrub becoming too large or congested.

 

The Japanese snowball v. plicatum should not be pruned unless there is a specific problem otherwise the appearance of the tiered branches may suffer.  If a damaged branch needs to be removed, do this in mid-spring.

 

Winter-flowering evergreens such as laurustinus (v. tinus) need no routine pruning, but if you want a more formal outline trim the plant to shape (Technique B) in late winter or early spring, using secateurs not shears.  For a compact bush, cut out one stem in 3 (Technique D) after flowering.  A neglected specimen can be cut back hard.  RHS: prune in early summer after flowering, renovate in summer.

 

V. opulus can be left unpruned to grow naturally.  To keep a mature bush compact and vigorous by encouraging new growth from the base, cut out one stem in 3 on mature plants (Technique D) in early summer every 3 to 5 years.  Any damaged or dead growth should be removed in mid-spring.

 

Most viburnums will shoot freely from the base or from older branches.  V. tinus responds particularly well to hard pruning if it becomes necessary, and will usually grow even if cut down to within about 30 cm of the ground in late spring.

 

Virginia creeper

Parthenocissus quinquefolia.  Leave it to grow.  Cut it back whenever.  It grows. [web note: not included in key words]

 

Vitis

Vines, such as Vitis coignetiae, growing through a tree or over a large pergola where space is relatively unrestricted, need no routine pruning unless they outgrow their allotted space.  If this happens, remove some of the oldest shoots and shorten young ones.  This is best done while the plant is dormant during the winter, but if the vigorous shoots become a nuisance, further pruning may be necessary during the summer.

 

Ornamental vines growing in a restricted space need to be pruned back to a framework of old branches in early or mid-winter.  Cut the shoots produced during the previous summer back to one or two buds from the old stem.  As these grow they can be trained to wires against a wall, or over an arch, trellis or pergola.

 

If space is very restricted and the young growth is too vigorous, cut the new shoots back to five or six leaves in mid-summer as the wood begins to harden and ripen at the base.

 

 

 

Techniques

Technique A: cutting back to the ground

Use this technique to improve the appearance of plants that throw up canes from a spreading clump, or to clear the old growth to make way for new shoots.  Working from one side of the bush, cut all the stems off just above the ground.  It is not necessary to worry about cutting back to a bud as new shoots will be produced from ground level.  After pruning, little will be visible except the short stumps of old shoots, but new ones will begin to appear within weeks, and by the end of the season will be as long as those just removed.

Technique B: clipping to shape

Clip back newest growth without cutting into old wood if possible.  Use shears for small-leaved plants, secateurs for large leaved plants.  If trimming in spring, only remove growth produced the previous year.  Remove the current year’s growth if clipping from mid-summer onwards.  Gives a neat shape.  Probably needs to be done annually to maintain shape.

Technique C: shortening sideshoots

You can increase the number of flowers the bush is likely to carry next year if you prune after flowering.  Select those shoots that have flowered.  This new growth is softer and paler.  Cut just above a bud about two-thirds down from the tip of each sideshoot that has flowered.  If you want to improve the shape of an old bush do not prune back too far.  Only cut into the previous season’s growth and then only to a point where this is a young shoot.  After pruning, the plant will retain its attractive shape and may not look very different from a distance, but this technique will help to keep the plants compact and encourage prolific flowering the following year.

Technique D: cutting out 1 stem in 3

Prune spring-flowering shrubs soon after flowering.  Remove 1 stem in 3, cutting them back to the base, just above ground level.  Choose the oldest or weakest branches to cut out first.  After the old and weak shoots have been removed, continue with those that will open up the centre of the bush or improve the shape.  You may not be able to see a bud to cut to, in which case leave a short stump.  This can be removed when the new growth starts.  After pruning the bush may look a little sparse, but new shoots will soon grow to fill the space.

Technique E:  Cutting back to a framework

Prune annually in early spring.  Cut back all the previous season’s growth to within about two buds of the stump of old wood.  This usually means leaving about 5 cm of last year’s stem.  If the bush has become very large and congested, cut one or two old stems down to ground level so that more of the plant’s energy goes into producing better flowers on fewer but better-placed shoots.  You will probably have to use long-handled pruners for this.  After pruning, only stumps will remain, but vigorous new shoots will soon grow and many shrubs will produce 1.8 m stems within a season.

Technique F: cutting back to a framework

Prune in early spring, before the new leaves appear, annually or every second year.  Cut back each stem to an outward facing bud about 5 cm from the stump of hard wood.  Within weeks of pruning, strong new shoots will grow. 

Technique G : cutting back grey-leaved plants

Prune regularly each spring, starting when the plants are young, as cutting back hard into old wood may spoil or kill the plant.  If new growth is present at the base, cut the stems back to within 5-10 cm of the ground.  On an established or neglected plant with a woody framework and no new shoots growing from the ground, be careful not to cut into old, dark wood.  Confine the pruning to shoots produced the previous year that are still soft, cutting them back to within 5-10 cm of the old dark wood.  After pruning the plants will look sparse but new shoots will soon grow, producing a much more attractive plant.          

PERENNIALS & HERBS

 

 

Alchemilla

Lady’s mantle

They prefer partial shade, but full sun is tolerated in climates with cool summers.  In mild-winter areas, the plants are evergreen.  Moist, well-drained, humus-rich soil is needed.  Plants readily reseed, so remove faded flowers if new plants are not wanted.  Plants seldom need to be divided, but can be after the fourth year if desired.  Plant in groups of three spaced 30 cm apart or use mass plantings as a ground cover.  Hardy to -40^oC.

 

Propagate by division in spring.

 

Seldom bothered by pests and diseases.

 

Anemone

Japanese anemone

The autumn-blooming varieties of Japanese anemone (a. x hybrida, also called a. hupehensis var. japonica) are some of the most handsome perennials for the garden.  The flowers are in shades of pink or white on slender, swaying, 60-90 cm, branched stems above 60 cm mounds of deeply lobed, dark green leaves.  Hardy to -34^oC. 

 

Autumn-blooming anemones must have partial shade or full sun in a location out of wind and a humus-rich soil that is moist in summer but well-drained.  A loose winter mulch of straw, oak leaves or evergreen branches is recommended for Japanese anemones.  They are best when planted in groups of three, spaced 45 cm apart. 

 

Propagate by root cuttings or division in autumn.

 

Pests and diseases: flea beetles; caterpillars; aphids; slugs; mosaic; rust.

 

Aquilegia

Columbine

These graceful plants are useful in sunny perennial plantings in cooler summer climates, but generally they do best in lightly shaded borders and woodlands.  The shorter types are excellent for rock gardens.  Well-drained but not overly dry soil is a must.  Plants readily self-sow.  Set plants 30 cm apart.  Hardy to -40^oC.

 

Propagate by seed.

 

Pests and diseases:  leaf miners; aphids; leaf spot; rust; mosaic.

 

Aster

Aster, Michaelmas daisy

Aster x. frikartii is considered one of the best perennials.  The open bushes grow 60-90 cm tall with fragrant, 5-7.5 cm lavender blue flowers produced over a long period in summer and autumn; these are excellent cut flowers.  Although hardy to -28^oC mulching with evergreen branches is necessary in areas with -23^oC or colder temperatures and soil must be well-drained.  In areas with a long growing season, pinch out the growing tips twice by midsummer to make plants bushy.  Stake taller varieties.

 

They do best in full sun in moist but well-drained soil that is average to humus-rich.  Mulch in late spring to retain soil moisture and water during droughts.  Deadhead regularly as plants readily self-sow but do not stay true to type and can become weedy.  Cut stems when flowering is over in autumn.  Stake tall-growing varieties.  Set plants 30-45 cm apart.  Asters do not grow well in hot, semi-tropical coastal climates.  Most varieties hardy to -34^oC.

 

Propagate by division every other year in spring or autumn (this is necessary with most hybrids).  Cuttings.  Seed.

 

Pest and diseases: tarsonemid mites; powdery mildew; root rot; wilt; slugs; caterpillars.

 

Aubretia

Purple rock cress

It thrives in full sun but tolerates partial shade and needs sandy, well drained soil containing lime and a cool, moist climate for best growth.  In areas with hot summers, plants are short lived.  Shear the plants back after flowering, except ones in walls, which should just be deadheaded.  Space 15-20 cm apart.  Hardy to -28^oC.

 

Propagate by division in autumn.  Cuttings in autumn and overwintered in a greenhouse.  Seed.

 

Pests and diseases:  white blister; mildew.

 

Bergenia

They grow well in light shade in hotter climates or in full sun in cooler areas and if soil kept moist; otherwise they tolerate a wide range of soil types.  Richer soil will require plants to be divided every three to four years.  Space plants 30 cm apart.  A winter mulch may be beneficial in areas with lows of -28^oC and colder.

 

Propagate by divison in spring or autumn, with each start having a 7.5-10 cm piece of rhizome.  Seed.

 

Pests and diseases:  leaf spot.

 

Digitalis

Foxglove

They grow best in a humus-rich, moist but well-drained soil and full sun or partial shade.  Remove faded flower stems if self-sowing is not desired;  this may also encourage re-blooming.  Set plants 30-45 cm apart.  Hardy to -34^oC.  A winter mulch of evergreen branches is helpful where there is little snow cover.

 

Propagate by division in spring after blooming.  Or by seed sown outdoors in late summer for flowers the following year.

 

Pests and diseases:  crown and root rot may develop if the ground is over-wet in winter.

 

Euphorbia

Spurge

Long-lived, these spurges grow best in full sun in dry, sandy soil. 

 

Light shade is beneficial in hot areas.  Plants readily self-sow.  Set plants 30-45 cm apart.  Hardy to -28^oC

 

Prune in midsummer, after flowering.  Prune back flowered stems to a strong shoot or bud low down, or to the base of the plant.  Plants will usually regenerate vigorously if all stems are cut back to the base in late winter or early spring, although the next season’s flowers will be lost.

 

They do not transplant well but, if necessary, divide in early spring.  Seed.  Cuttings.

 

Pests and diseases:  grey mould.

 

Ferns

In general, they grow best in a shady location with humus-rich, loose soil that is moist but well-drained and a light mulch of compost, bark, or shredded leaves.  Set plants 30-75 cm apart.  Hardy to -40^oC.

 

Division of creeping types at any time and ones with crowns when dormant in early spring or late autumn.

 

Pests and diseases:  some ferns may be bothered by slugs, snails and rust.

 

Geranium

Crane’s-bill

The lilac crane’s bill is G. himalayense, but it may also be listed as G. grandiflorum or G. meeboldii.  Spreading mounds combine with 5 cm blue flowers with purple veins. 

 

Blood-red crane’s-bill (G. sanguineum) forms a mount 30-45 cm tall with long-blooming, 2.5 cm, pink to magenta flowers.  It is highly adaptable to various climates and also self-sows readily.  If the soil is too rich, it will spread excessively.  Foliage turns deep red in autumn.

 

They bloom best in full sun, but in hotter climates plants grow better with light shade.  Average, moist but well-drained soil is best; overly rich soil encourages rampant growth.  Set plants 30 cm apart.  Hardy to -34^oC.

 

Propagate by division in spring every 4 years or when clumps begin to deteriorate.  Seed for species (??).  Cuttings in summer.

 

Pests and diseases: slugs.  Rust is more prevalent on wild geranium species. 

 

Grasses

They tend to like full sun and a humus-rich, moist but well-drained soil.  Average to poor soil and dry conditions are usually tolerated.  Trim plants back to ground level before growth begins in the spring.  It may take several years for ornamental grasses to become established.  Generally hardy to -34^oC.

 

Helleborus

Hellebore

Lenten rose (h. orientalis) blooms from late winter through spring with 5 cm flowers that may be cream, purple-pink, maroon-brown, or greenish-white, sometimes with rose-purple spots.  This 45 cm tall species hybridizes readily and there are many forms, all of which are among the easiest to grow of the hellebores.  Hardy to -34^oC.

 

Ideally they need sun in the winter and shade in the summer, with a humus-rich, neutral, moist but well-drained soil.  Planting under deciduous trees or among other perennials are ways of achieving this.  Do not allow soil to dry out in summer; a mulch is beneficial.  Set plants 45 cm apart with the crown 2.5 cm below the soil line and allow several years for the long-lived plants to become established before they bloom well.  Winter protection of various types may be used, including mulching loosely with oak leaves, covering with pine branches or building a plastic-covered frame to set over plants.

 

Propagate by division of the roots in spring after flowering or in autumn is possible but not recommended.  Or by seed sown as soon as ripened.

 

Pests and diseases:  leaf spot.

 

Heuchera

Coral bells

They grow best with a humus-rich, moist but well-drained soil.  Good drainage in winter is essential.  Choose a site with full sun or light shade, with the latter preferable hot, dry climates.  Space plants 30 cm apart and set crowns 2.5 cm deep in spring.  Deadhead regularly to prolong blooming.  Hardy to -40^oC.  Mulch with evergreen branches after the ground has frozen to prevent winter heaving of roots.

 

Propagate by division in spring or autumn, usually every three to five years, or when the crown becomes woody.  Younger plants can be divided for increase.

 

Pests and diseases:  leafy gall.

 

Iris

Unless otherwise noted, they grow best in full sun but tolerate light shade. 

 

Bearded, crested, Siberian, and roof irises need a humus-rich, moist but well-drained soil with the rhizomes 2.5 cm below the soil surface. 

 

Except as noted, deadhead regularly.

 

Set shorter types 30 cm apart and taller types 45 cm apart.  Hardy to -28^oC.

 

Propagate by division of rhizomes after flowering.  Bearded iris usually need dividing every three to four years.

 

Pests and diseases:  prone to a number including iris borer followed by bacterial soft rot, evidenced by trails of slime along leaf edges.  Begin spraying in spring and repeat weekly for 3 weeks; remove and destroy infected rhizomes at any time, and old foliage in the autumn to prevent overwintering borer eggs.

 

Kniphofia

Torch lily, red hot poker

They grow well in full sun with humus-rich, moist but well-drained soil.  Wet soil in winter is usually fatal.  Avoid windy sites as plants are difficult to stake.  Set plants 45 cm apart, planting in spring.

 

Propagate by division in early spring every 4 or 5 years, if desired, removing young side growths or digging the entire plant and separating.

 

Pests and diseases: thrips.

 

Lavandula (see also entry under shrubs)

Lavender

It needs full sun and sandy, alkaline, well-drained soil that is not too fertile.  Prune back old wood in the spring.  Set plants 30 cm apart.  Hardy to -28^oC.  A winter mulch in climates of -18^oC or colder is necessary.

 

Propagate by cuttings in early summer or seed.

 

Pests and diseases:  froghoppers; leaf spot.

 

Papaver

Oriental poppy

They are easily grown in full sun with average well-drained soil.  Poor drainage in winter is usually fatal.  Staking may be necessary with taller types.  Set plants 45 cm apart, with the crown 7.5 cm deep.  Hardy to -34^oC.  Both a summer and winter mulch is beneficial.  Best left undisturbed for 5 years.

 

Propagate by division in late summer or autumn when new growth appears.  Root cuttings in late summer.

 

Pests and diseases:  downy mildew.

 

Sedum

Stonecrop

The showy stonecrop (sedum spectabile) grows 60 cm tall with pink flowers.

 

Tough, adaptable and easily grown, they tolerate a wide range conditions, but do best in full sun and any well-drained soil.  Set shorter types 30 cm apart and taller ones 45-60 cm apart.  Hardy to -34^oC.

 

Propagate by divison in spring or by cuttings in summer.

 

Pests and diseases:  rust.

 

Stachys

Lamb’s tongue

S. Byzantina also listed as s. “olympica lanata” forms 60 cm ground-hugging mats of 10-15 cm long white, thick, softly furry leaves with 5 cm spikes of 12 mm magenta flowers.  The flowers are produced intermittently all summer; some gardeners prefer to cut them off to improve appearance and prevent self-sowing.  This long-lived species makes a dense ground cover accent for the front of beds and borders, in a rock garden, or as an edging.

 

Grows well in poor to average, well-drained soils.  Plant in full sun.  Set plants 30 cm apart.  Hardy to -34^oC.

 

Propagate by division in spring or autumn, every fourth year or when plants die out in the centre, or by seed.

 

Pests and diseases:  seldom bothered, except that lamb’s tongue may rot in hot, humid climates.

 

Humulus

Hop

Fully hardy, herbaceous, twining climbers with lobed leaves; female plants bear pendent clusters of greenish-yellow bracts (“hops”).  They are vigorous, forming an effective seasonal disguise for unsightly structures, or they can be grown on stourt arches or tripods.  Shoots are fragile.  Hops die back in winter; in early spring, cut the dead growth down to ground level.

 

 

Allium shoenoprasum

Chives

 

Foeniculum vulgare

Fennel

 

Mentha spicata

Spearmint