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.