Pruning shrubs: when and how

Val Bourne

Tidying up a garden full of shrubs can seeming a daunting task. Sop what's the best way to prune them without causing damage to them?



Most shrubs benefit from regular pruning to remove old wood, improve shape and encourage flower. However there are some exceptions. I never prune daphnes and I am equally reticent about witch hazels (or hamamelis). Magnolias need care too. Prune in June if they need it.

Buddlejas, or butterfly bushes, flower on strong new growth. Cut them back hard in April to keep them a manageable shape and to encourage large, late-summer flowers. However, if earlier flower is required, prune them in September reducing the growth by a third. Mediterranean sub shrubs (artemisias, santolinas and anthemis) are left intact over winter and then cut back hard in April to maintain vigour and form.

Most hardy shrubs flower on the previous year's wood. Generally if it flowers before mid-June it should be pruned straight after flowering. However, if it flowers later in the year, wait until late winter or early spring. The technique is to cut between a fifth and a third of the old, darker wood away. This gives the maximum time for regrowth and also leaves two thirds of the mature wood intact - ensuring flower for the next season.

Thinking time

Sometimes when you take over a garden the shrubs have been allowed to become old and leggy. My advice would be to stand back and watch for a year to see what you have in your garden. Then you can make a decision about whether you want to keep it or not.

If you decide to scrap it, autumn is generally the easiest time to get something out. It also allows you a couple months to decide what to replace it with in the following spring.

Rejuvenating an overgrown shrub

If you decide to keep it, you will need to do some radical pruning (probably in early spring) and this may result in the shrub dying. You could take some insurance cuttings in late-summer and autumn. Look for new growth that doesn't have any flower. If the wood is hard and brown, sink the foot-long cuttings into a trench in the garden. Just get a spade when the soil is damp and make a narrow gap by 'waggling' the spade. Leave the cuttings for a year. If you are on heavy soil dig a narrow trench and put sand into the bottom of the trench to aid rooting. semi-ripe cuttings that are still pliable can be trimmed under the node and plunged in a 50% mix of grit and compost. Leave them to root in the greenhouse away from overhead sun.

The rejuvenation involves two or three stages and will take at least two years. In the first year, prune deciduous shrubs by taking a third of the wood back to the base and leaving two-thirds intact. Take another third in the following year and then the remaining third in the next. This is an excellent technique and you will end up with a vigorous plant if the shrub responds. You will know after the a year whether it is working.

Evergreens

A few evergreens (like yew) respond to this three-year regime. Mostly conifers will not regenerate from old wood.

If you are dealing with an overgrown holly it is not fast growing enough to spring up from the base and grow away quickly. Hollies are slow-growing and they need to be hat-racked. This preserves the height and ‘hat-racking’ can also be used with yew trees.

Hat-racking an old holly or yew

This is done in two stages. Begin by reducing the width of the yew or holly by cutting back most of the branches to eighteen inches or two feet in length. The bare stems radiate from the trunk and resemble a hat rack, or mug tree. The dormant buds respond and soon grow away and bush out. Leave the tree to recover and fill out for two years before reducing the height. At this stage you can cut the top off and you will end up with a rejuvenated holly or yew.

Deciduous shrubs make perfect partners for woodland plants

Gardens with lots of shrubs needn’t be boring. If they are deciduous they make ideal partners for a whole range of spring-flowering woodlanders. You can maximise the space by lifting the skirts of your established shrubs. Remove any lower branches up to two to three feet above the ground. This will one main stem which you can then plant right up to.

Ten of the best spring-flowering woodlanders

1. Pulmonaria 'Diana Clare'

This silver-leaved pulmonaria has frosted leaves with a green verdigris caste. The flowers are an exciting violet-blue and it’s arguably the best pulmonaria ever. Found as a seedling on Bob Brown’s Cotswold Garden Flowers and named after his wife.

2. Anemone nemorosa 'Vestal'

A double-white wood anemone with a neatly formed flowers and one of the better ones at bulking up.

3. Galanthus 'Viridapice'

A snowdrop with green-tips to the petals. It bulks up well and has a good presence in the garden. (from Avon Bulbs)

4. Narcissus 'Jetfire'

About a foot tall, this extremely jaunty daffodil has an almost-red trumpet and clean-yellow outers. One of the best at standing up to the weather.

5. Scilla siberica

The Siberian squill has gentian-blue flowers and reaches six inches at most - particularly good with yellow daffodils.

6. Pulmonaria 'Blue Ensign'

A deep gentian-blue pulmonaria with plain-green leaves and vibrant flowers. The purple buds are a real feature too.

7. Helleborus x hybridus

The oriental hellebore is a glorious early plants and, if you can find a strong green or white form, these glow in late-winter and spring.

8. Dryopteris wallichiana

Black-bristled hairs contrast against bright green fronds when this handsome upright fern unfurls its croziers in late April.

9. Cyclamen coum

Jaunty swept back flowers with a magenta nose, followed by rounded leaves which can be silvered. Grow cyclamen coum in full sun, or under trees and allow to self seed.

10. Brunnera macrophylla 'Jack Frost'

Heart-shaped silvered leaves dramatically edged and veined in green, finished off with dainty blue flowers.

 


The opinions expressed are those of the author and are not held by Saga unless specifically stated.

The material is for general information only and does not constitute investment, tax, legal, medical or other form of advice. You should not rely on this information to make (or refrain from making) any decisions. Always obtain independent, professional advice for your own particular situation.