Pruning Hydrangea paniculata

Hydrangea paniculata is a class act. The showy clusters of flowers (panicles)  appear in late summer just as the garden is losing its summer appeal and give a welcome boost to beds and borders. The showy flowers range from pure white to deep pink and the colour does not vary according to the acidity of the soil. 

Like so many plants, the pruning regime depends on the effect that you want to achieve. Light or minimal pruning will result in many small flowers and harder pruning will give fewer but larger flowers.  You may wish to leave unpruned for a few years and renovate large shrubs once in a while. As with all shrubs that flower from mid summer onwards, prune just as growth commences in spring.

Hydrangea paniculata

Pruning a Catalpa bignonioides for foliage effect

The Indian bean tree- Catalpa bignoniodes may be saddled with a cumbersome botanical name but it is a glorious plant. Left to its own devices, it grows into a large tree with very attractive summer flowers. It is more of a tree for large gardens and parkland, but can still be grown in small gardens provided it receives an annual hard pruning in spring. Like Paulownia tomentosa mentioned in a previous post, hard pruning results in spectacular bold foliage but sadly, flowers are forfeit. 
Pruning is best carried out in spring at the commencement of new growth. The picture below shows an expertly pruned specimen at the gardens of the Royal Horticultural Society at Wisley.

Luxuriant foliage from a yellow leaved Catalpa as a result of hard pruning

Pruning willows for coloured bark

Willows can provide much needed winter interest with colourful stems but as this is only on young (current season's) growth, a hard pruning regime is necessary to maintain the colour and stop the plants becoming too big for the garden. 

I was working at the Royal Horticultural Society's garden at Wisley, Surrey doing my tutoring role for the Master of Horticulture and whilst walking in the gardens, I saw these willows that hard received the hard pruning necessary to provide winter interest. You may be surprised at the apparent savagery but willows are very forgiving. If you need more plants, insert the prunings (making sure that they are the right way up) into some moist soil and they will root and grow into new plants. Alternatively a basket maker will certainly take away your prunings, I suggest swapping them for something as they are valuable. 

If you are a timid pruner, I suggest pruning coloured bark willows when you are in a very bad mood! 

Cotinus- an irritating plant

Cotinus coggygria 'Royal Purple'- the purple leaved smoke bush is a stunning foliage shrub with rich coppery purple foliage and masses of curious small flowers in summer that appear as a haze of smoke. Like many foliage plants, the colour of the leaves is best on young growths and that may necessitate hard pruning. This pruning is best carried out in spring as soon as growth commences.

So why is the plant irritating?   The problem is that the plant is related to the notorious poison ivy of North America. If sap exposed by pruning cuts comes into contact with your skin, you may suffer nasty and long-lasting irritation. There is no need to panic, just ensure that you wear long sleeves and protective gloves when pruning this plant and avoid carrying out this operation on a sunny day as the sap can cause hypersensitivity to sunlight. 

I also find that the sap can coat pruning tools such as saws so clean them carefully after use. 

Large pruning cuts of Cotinus should be treated with care to avoid possible irritation. 

THE ARS long reach pruner

I love using quality tools and avoid using ladders at all costs when pruning. This is particularly true if the ground is uneven or soft, as it often is in rain soaked Wales. When I needed to reduce the height of this over vigorous specimen of Cotoneaster salicifolius growing on a steep bank, I reached for my ARS long reach pruner and did the job from the safety of a level terrace. 

The tool was not cheap, it cost me nearly £100 but I never regret investing in quality. I have a Bahco long reach pruner that cost about the same amount but it is less convenient to use as the cutting mechanism is operated by a pull cord that annoying wraps itself around  the shaft of the tool and needs frequent untangling. 

The ARS pruner is like a giant pair of secateurs in which the handles are separated from the blades by a long, lightweight shaft. The tool cuts cleanly and I keep the blades sharpened (please see my earlier posts about sharpening). It is worth remembering that this is a modified pair of secateurs and so should never be allowed to cut thick stems. The Bahco pruners can cope with a little more abuse and if they cannot cope, I use my trusty Silky Fox Zubat pole saw. 

My ARS pruner is an invaluable part of my pruning toolkit. 

Putting gooseberry prunings to good use

I recently bought and planted some gooseberry bushes and cut back the main stems to promote bushiness, Rather than wasting the prunings, I inserted them into a pot of growing compost and left them to root. A month or so later, all have rooted with no requirement for rooting compound or special care and attention. The pot was left outside and watered by our generous rainfall. Blackcurrants, red and whitecurrants can be easily propagated from leafless previous season's growth taken from prunings.  In the case of blackcurrants which are very easy to propagate, make sure that healthy growth is selected without any signs of abnormally big buds indicating  gall mite damage. 

I obtained 100% success with these cuttings and all have started to grow strongly and will give me plants for my gooseberry hedge in the autumn. This is a good return on an investment of a few minutes of my time and a small quantity of potting compost. 

Hardwood cuttings of gooseberry made from prunings

Some great ideas for fruit trees

I am lucky that I have the opportunity to visit some of the Royal Horticultural Society gardens as part of my work. A visit last month gave me the opportunity to see some clever training of apple trees as double cordons creating a brilliant effect as well as abundant fruit.

Cordons need careful summer pruning to restrict vigour but allow easily access to fruit and are attractive in their own right, They also allow several varieties to grow in one small space meaning you can have a reasonable quantity of fruit from several varieties rather than a mass of fruit all at one time from a single variety.

Straight or slanted cuts for roses?

I was recently examining Royal Horticultural students for their Wisley Diploma and was discussing the rose pruning practical with my good friend and expert horticulturist, Mr Ray Broughton. 

We were discussing the assessment criteria and Ray informed me that it is RHS policy to use straight (horizontal) cuts when pruning roses rather than slanting ones. Until recently, we were advised to make slanted cuts at an angle of 45 degrees to the main stem to prevent water settling on the pruning cut and encouraging fungal infection. Now I have never agonised over the angle of cut as rose stems are seldom vertical and as long as the cut is made cleanly just above a bud with a sharp pair of quality secateurs, you will be fine. 

My point is that you will never find consensus amongst horticulturists about rose pruning, there are still some who advocate the use of hedge trimmers ( I do not) and  have their own techniques at variance with others. If your rose pruning technique works, stick to it.

There are so many ways to prune roses

Make tidy cuts

I am always on the lookout for good and bad pruning and came across this poor specimen of Elaeagnus x ebbingei. The untidy pruning cuts looked a mess and worse still, they will take a long time to heal and this will greatly increase the risk of bacterial and fungal infection. This is a mistake that could prove fatal for the plant. I am sure that a badly sharpened hedgetrimmer was used to butcher this plant. 

If you must use a hedgetrimmer on your shrubs, please tidy up the pruning cuts with a sharp pair of secateurs, treat your plants with respect and they will reward your efforts.

  

Pruning rambling roses

Rose pruning can be a little daunting with so many different types. Rambling roses are vigorous plants that are used for scrambling into trees or covering pergolas or garden structures. The curved thorns act as grappling irons to gain purchase on bark or woodwork. A relatively plain shed or garden building can be transformed by a covering of a rambling rose. 

Rambling roses need to be distinguished from climbers as they have different pruning requirements. Ramblers tend to be very vigorous, have semi-evergreen foliage and flower in a single flush. By contrast, climbers have stiff stems and are usually repeat flowering. There are exceptions to these rules, some ramblers are repeat flowering and some climbers have only a single flush of flowers.

Left unpruned, ramblers often become a mess of tangled shoots and as vigour declines, so does flowering. You need to be prepare to make some some hard pruning cuts to keep your ramblers from becoming triffids and I suggest using both secateurs and loppers. 

Pruning ramblers is about removing flowering shoots close to their point of origin at the base of the plant immediately after flowering. Do not overwork your precious secateurs, a pair of loppers will save time and avoid twisting the blades of your secateurs. What proportion of flowering shoots you remove depends on your requirements, if the plant is threatening to outgrow its allotted space, take them all out leaving the new shoots to flower next year. If there is enough space to accommodate them, leave the majority of flowering shoots in place and take out either a quarter or third of them each year taking out the older shoots on a rota basis. Side shoots are reduced by about a half. 

Pruning ramblers appears brutal and is not a task to be undertaken by a gardener who is timid with the secateurs. 

Rosa mulliganii - a typical rambling rose needing pruning after flowering to keep in check. 

How not to prune a spring flowering Spiraea

Spring flowering Spiraeas usually have naturally arching growth giving them as graceful habit. This habit can be ruined by thoughtless pruning, I came across this specimen recently. The poor plant had had the hedgetrimmer treatment cutting off the young growth and destroying its graceful habit. No doubt the handiwork of a 'professional gardener'. Please avoid the temptation to prune shrubs like hedges, the time saving is minimal and the effect unforgivable. 

Dealing with Salix caprea Goat willow

Often when I look at shrub plantings that are maintained by contractors, the goat willow (Salix caprea) is able to grow as a woody weed amongst the shrubs and it is either ignored or is given a annual 'prune' with a mechanical hedgetrimmer. Salix caprea is a common weed of nursery plants and may have been present in the pot when the plant was planted out. The seeds of this willow are commonly distributed by wind  and the irrigation water of nursery plants that are watered from water from a reservoir. The plant may be welcome in the wild but rapidly swamps shrubs if left to flourish. 

The ideal solution is to pull up small seedlings but if the weed is too large to do this, either cut back the willow to ground level and apply an approved  systemic weedkiller to the stump or remove it with a mattock or grubbing axe if this is possible. The sooner the weed is treated, the better. 

The goat willow needs prompt removal to prevent it becoming a menace in shrub plantings. 

Pruning Paulownia tomentosa

Paulownia tomentosa (foxglove tree) is a spectacular tree when grown for its very large, handsome leaves or its fragrant foxglove like flowers in spring. It is only in sheltered locations in southern England that the flower buds that are formed in autumn survive the winter unscathed to produce a stunning flowering display. In places that do not experience a mild winter, it is best to forget about flowering and give the plant a hard prune in spring to encourage strong new growth producing exceptionally large leaves. 

Large, handsome leaves from a Paulownia tomentosa hard pruned in spring. 

A Paulownia tomentosa pruned hard in spring. 

Pruning an established Choisya

Choisya are firm garden favourites that are relatively undemanding in terms of maintenance. They can be depended to put on a showy display of white flowers in spring. They are one of those plants that can put on a lot of growth particularly in a sheltered location. They are tolerant of quite hard pruning once established provided that the plant is healthy and growing strongly. Once flowering has finished, a light prune will encourage a second flush of flowering in autumn. 
if plants have been pruned more severely, an application of a Potassium rich fertiliser  will help to ripen wood and improve the frost resistance of young shoots. 

Now this specimen of Choisya x dewitteana 'Aztec Pearl' has finished flowering, it can be pruned if required. 

Pruning the shrub rose Rosa 'Helen Knight'

Shrub roses are undervalued and some such as 'Helen Knight' are worthy of more recognition. What is important with shrub roses is not to prune them like hybrid teas or floribundas, they need a much lighter pruning regime. This rose flowers on older growth so an early spring pruning that is given to hybrid teas and floribundas will take off most of the flowers. 

The graceful, arching stems add to the appeal of this early flowering rose. Prune a selection of older stems out close to the base of the plant to restore the right balance of old and new wood. This operation should be carried out immediately after flowering. 

Cutting back rather than cutting out stems will destroy the arching habit. Use the loppers rather than secateurs on this plant and it will be a delight in spring. 

Rosa'Helen Knight' in full flower in spring.

A pruned plant showing the complete removal of shoots at the base after flowering to encourage strong basal growth

jhg

Pruning Physocarpus 'Diablo'

Physocarpus opulifolius 'Diablo' is in my opinion, a first rate foliage shrub. It was discovered as a chance seedling in a batch of Physocarpus plants. Its rich coppery purple foliage adds a bit of excitement to borders and its generally trouble-free constitution is an added bonus.

The plant produces small clusters of flowers in spring followed by red berries. Although these flowers are attractive, they are not the main feature of the plant. I advocate hard pruning of all stems in March to get maximum foliage effect but if you want to retain the flowers and fruits, cut back a selection (say a third) of shoots at ground level to encourage vigour but keep some flowering wood. The fruits are eaten by birds.

A few stems of this plant can be cut back in autumn and made into hardwood cuttings that can be rooted outdoors or in a cold frame. This is a good idea as I find the plant somewhat short-lived. The fast growing nature of this plant makes it an ideal 'filler' for borders before the permanent plants become established. 

Physocarpus opulifolius 'Diablo'. Rich foliage colour on a hard pruned plant. 

Pruning the shrub rose Rosa glauca

Shrub roses generally have minimal pruning, usually confined to the removal of old, unproductive shoots at the base at the commencement of growth in spring. There are different systems for different shrub roses, early flowering types that flower on wood made the previous season are usually pruned immediately after flowering. 

Pruning is about getting what you want from the plant rather than following the dictates of text books (and people like me!). There will always be exceptions to the 'rules' and one such exception can be Rosa glauca. Rosa glauca is a plant indigenous to southern Europe and has distinctive coppery grey foliage and small pink flowers followed by red fruits. The stems are mercifully devoid of spiteful thorns. It is also known by its synonym Rosa rubrifolia. 

The best foliage is obtained by hard pruning in spring, I know one head gardener of one famous garden in England who pruned his specimens to ground level every March. This will create vigorous growth at the expense of flowering. Flowers will appear on hard pruned specimens but will be be fewer in number and appear later than plants that have been pruned more lightly. The choice is yours. 

Rosa glauca- prune it to achieve the effect you want

Renewal pruning Pyracantha

Some plants can become too big for their allotted space and need either drastic pruning or removal. there is always an element of risk with hard pruning, some otherwise healthy looking plants do not survive the trauma and others grow away with a new lease of life. Most vigorous shrubs like Pyracantha seem to survive drastic pruning. If you are worried out killing your plant, shorten back half the stems, if these grow back after pruning, do the rest the following year. 

The best time to do drastic (renewal) pruning is in spring as this will give a full growing season for the new wood to 'ripen' before the onset of winter. This will avoid frost damage to new shoots. I suggest applying a Potassium-rich fertiliser in mid summer to assist with ripening the wood.

The picture below shows new shoots developing from a Pyracantha that I hard pruned a month ago. The plant will have a new lease of life and its neighbours will no longer suffer from competition with this vigorous plant. 

Summer pruning apples

Summer pruning is a useful technique for apples grown on restricted forms such as fans, espaliers, codons and dwarf pyramids. It helps to restrict vigour and allows light to get in  to the developing fruits to improve sweetness in eating varieties and improve colour. I tend not to use this technique on bush and standard trees as it can be time consuming and there is never a shortage of things to do in summer. Summer pruning espaliers, cordons and fans is a relatively quick task and is essential for best results.

Summer pruning in the UK is usually done from mid July to September. All you need to do is to prune the shoots that grow from the main branches (laterals) than have grown in excess of 20 cm (8 inches) and cut these back to about three buds (you do not need to be precise). Any laterals than have not grown in excess of 20 cm are best left unpruned and may well develop fruit buds at their tips. Strong vertical growth is unproductive and will result in excessive vigour at the expense of fruiting. These strong vertical shoots need complete removal and this is where a pruning knife can come in handy. Do no leave a stub as new growth will follow and you will need to cut these out. Take the shoots out at the very base and do not worry about leaving a small wound, it will heal very quickly in summer. 

Any secondary growth from shortened laterals can be removed in September.

Start to summer prune cordon, espalier and fan apples in July

Espalier apples

Fasciation

You may have come across a unusual growth on a shrub or herbaceous perennial. Several stems appearing flattened and fused together may appear on Forsythia or Salix and this could be 'fasciation'. I have photographed some fasciation on Euphorbia that I came across several years ago. 

The photograph shows both fasciated and normal non-fasciated growth. There is nothing to worry about fasciation, some people find it attractive, others find it ugly. The causes of fasciation are not clear, it has been linked to insect damage, frost or mechanical damage through cultivation and possibly virus infection. 

If you find fasciated growth ugly, cut it off. If not enjoy this curiosity. There are some varieties of plants actually cultivated for their fasciated growth! if the plant is a Euphorbia, please note that the milky white sap that oozes out of pruning cuts can irritate skin so wear gloves and avoid pruning in strong sunlight.