Training and Pruning

 
 

Why and How to Coppice Eucalyptus

In this section you will find information on the following:-

General notes on the practice of Coppicing

Eucalyptus and coppicing

Size of tree to coppice

Time of Year

Technique

Choice of species for Cut Foliage

Species to avoid coppicing

 

General notes on the practice of Coppicing
Coppicing is an old horticultural technique whereby a tree or shrub is pruned down to or near ground level. This stimulates the buds around the root collar and lower part of the trunk or stem into frenetic growth; many new shoots are produced.  
This method is used to

  • rejuvenate old shrubs that have become leggy or lack vigour
  • renovate an old hedge that is used to being hard pruned such as Beech, Hornbeam or Yew
  • control the vigour of large trees and shrubs
  • produce a multi-stemmed tree or shrub
  • produce a crop such as Ash for firewood, Hazel stems for bean sticks, Willow for biomass and charcoal
  • encourage young ornamental juvenile stem growth in Dogwoods (Cornus sibirica 'Westonbirt') and Willows such as Salix acutifolia 'Blue Streak'
  • encourage large leaves in Paulownia tomentosa  and Catalpa bignonoides when grown as a shrub

The time of year that this activity is carried out is species specific, but in the main, coppicing is done while the plant is dormant in the winter months, except Eucalyptus which need to be done in the Spring.

Eucalyptus and coppicing
The biology of Eucalyptus is such that many species lend themselves to coppicing.  All species that produce a lignotuber (and some Eucalyptus do not) will respond well to the practice.  
Click here to read more about the lignotuber.

Eucalyptus are coppiced for the following reasons:

  • To control growth so that a large tree can be grown and enjoyed as a shrub
  • To reduce wind-throw and stabilise the tree.  It can be allowed to grow out of this at a later date, to produce a larger tree as required
  • To produce juvenile cut foliage for flower arranging either in your own garden or as a commercial crop
  • To produce a crop of firewood logs click here to read more about grow your own firewood

There are two different heights to prune down to, depending on what you want to achieve with your Eucalypt.

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Size of tree to coppice
Allow your newly planted young Eucalyptus two full growing seasons in the ground before coppicing. Ideally, the diameter of the trunk at the base of the tree needs to be in excess of 50 mm (2 inches) before you prune it down.  This  means that the the tree is now of a size whereby  the root system has established well into the surrounding  soil and built up sufficient reserves to allow regeneration after coppicing.

Coppicing removes the food factory of the plant as well as the suppressant growth hormones (the chemicals produced in the shoot tips that prevent side shoots from growing) . Therefore, immediately after pruning down, the dormant buds in the trunk and lignotuber have to rely on the food stored in the root system for an emergency energy supply, until they have produced leaves to photosynthesize.

Coppicing a young tree that is not large enough to undergo the process may kill it.

There is no upper age limit for the practice; quite large and mature, old  trees can be coppiced, provided they are of the right species.

Time of Year
For Eucalyptus - beginning of March up to beginning of May

Avoid carrying out this practice from October onwards and certainly not during the winter months.

Autumn is too late to allow the pruning wound sufficient healing time before the onset of heavy frost, which can cause the bark to delaminate from the main trunk.

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Technique
Using sharp bypass loppers or a very sharp saw if the trunk is very large, prune down to the stump and remove all side shoots with secateurs or loppers. The latter is important to force the lignotuber and subcutaneous shoots to break dormancy, otherwise the Eucalypt with generate weak shoots off the thin side shoots, which is undesirable. The height of the residual stump varies according to your end goal.

Height to prune down to
The choice is between pruning down to 100-120 mm (about 4-5 inches) or pruning down to 450 mm (18 inches).  There may not seem to be a large enough difference between the two sizes, but our trials in the nursery have shown that there is a different shooting response from the tree, dependant upon the residual length of the trunk.

Coppice method 'A', if the goal is to:

  1. To reduce instability in a young tree (coppice at the age of 3 years +)
  2. Control height of a tall species on a regular basis (coppice every 3  years or so)
  3. Produce  firewood production (carry out coppicing every 8 years)

The ideal height for cutting down to is 100-120 mm (about 4-5 inches).

  • Use a slanting cut to disperse sap and rainwater away from the wound and preferably facing south so the sun can aid drying and healing the wound.
  • Remove all side shoots.
  • Tidy up any jagged edges.  Remember to treat the wound with a proprietary pruning compound, available from your local garden centre.

The bark may loosen if the cut is made lower that 100 mm, at ground level

If the cut is made much higher than 150 mm, you are not activating the strong buds near the root collar and for a mature tree, you are reducing its long term success rate of the operation.

About six weeks or so, after pruning down, you will see a mass of new shoots emanating from around the base of the trunk and also from the trunk itself.  As the growth hormones in the new shoot tips begin to flow, dominance is re-instated and the largest thickest shoots, highest up the stem tend to take over. These suppress further bud and young shoot development.
Finally a handful of shoots will lead the way and you have the choice to select the best to grow up as a single trunk or a group of three as an attractive multi-stemmed tree (which is also best for fire-log production)

Windward side shoots are preferable to leeward side shoots, because they are less likely to be wind-thrown in bad weather (i.e. peel off in a gale).

If your plan is to re-grow the new shoot up into a new tree trunk, you will find it best to select a shoot nearer to the root collar as possible. The callous tissue is stronger lower down, has better attachment to the stump, creating a more stable new trunk. The further up the trunk, the weaker the callous and therefore these shoots are less stable.

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Coppice method 'B', if the goal is to:

  1. To produce cut foliage for flower arranging
  2. To grow for ornamental juvenile foliage 
  3. To keep as a manageable shrub rather than a tree

In this instance, the ideal height for pruning is 450 mm (about 18 inches)

  • Use a slanting cut to disperse sap and rainwater away from the wound and preferably facing south so the sun can aid healing the wound.
  • Remove ALL side shoots.
  • Tidy up any jagged edges.  Remember to treat the wound with a proprietary pruning compound, available from your local garden centre.

Young buds can be seen breaking dormancy after about 4 weeks.  Shoots will be about 400-500 mm long by 8 weeks and grow quickly over the summer months. This is when some additional irrigation may be helpful if rainfall is sparse.

By the Autumn, new stems will be anywhere between 600 and 1200 mm long and ready for harvesting.
Shoots higher up the stem will be longer, whilst shoots lower down will be shorter, being suppressed by their taller siblings.

For cut foliage production, you can pick the shoots any time after they have ripened in the Autumn, between October and March.  Now I know that this is a contradiction, first we say don't prune in the winter and then we say pick your foliage in the winter.

We have been advised by commercial foliage growers that the stems are harvested in the winter months, because that is when the wood is ripe (firm) and not actively growing fast and therefore fleshy and prone to wilting.  The stems are good for floristry work, but the tree is at risk of suffering frost damage, especially if grown in a particularly cold part of the UK.  Most commercial producers are to be found on the west coast of England and Wales or in Ireland, where they escape the harsh winter weather.

If you wish to use your Eucalyptus for floral art click here to see our notes on conditioning and preserving.

Alternatively, if you are growing the Eucalypt purely as an ornamental garden shrub, leave it for a further growing season before you coppice it again.

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Choice of species for Cut Foliage
The juvenile form of the Eucalypt is favoured by florists and flower arrangers, being distinctly different from the more elongated mature foliage. Juvenile foliage often has the best range of colours,  silvery blues suffused with white, shades of pink, violet and burgundy and sometimes a little bright acid green.

Many species are used in traditional arrangements and bouquets.  In particular the Silver Leaved Mountain gum (E. pulverulenta) and the smaller (E. pulverulenta 'Baby Blue'), Small Leaved gum (E. parvula) and Cider gum (E.. gunnii) are very reliable and popular.  

The feathery foliage of Narrow-leaved Black Peppermint (E. nicholii)  is delicate looking and especially attractive.

However, the Spinning gum (E. perriniana) is very effective in modern installations.

The Candle Bark gum (E. rubida) is new and gaining ground as a red stemmed species with tones of pink/violet and burgundy in the new shoots.

Click here to be taken to our flower arranging collection in our shop

Full species recommended for cut foliage:

E. archeri                    

E. coccifera                   

E. crenulata

E. glaucescens          

E. gunnii                         

E. gunnii divaricata

E. nicholii                    

E. parvula                       

E. perriniana

E. pulverulenta           

E. pulverulenta 'Baby Blue'

E. risdonii in sheltered areas

E. rubida                    

E. stellulata

E. subcrenulata

E. urnigera

Species to avoid coppicing
Avoid the following species for foliage production as they have poor coppicing ability:

E. delegatensis

E. fraxinoides

E. nitens but it will regenerate sufficiently to be used as one of the standard species used in firewood production, but will need re-planting after 24 years (i.e. 3 rotations)

E. pauciflora group but will grow back from their lignotuber, but generally are poor at coppicing

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