Training and pruning
Growing Method for a Feature, Single Stemmed, Specimen Tree
Many Eucalyptus produce very stately specimen trees, making an excellent focal point. They add structure to the winter garden with interesting evergreen foliage, architectural habit and beautiful bark.
A specimen tree has a clear trunk for about the first two metres followed with a head of well-placed branches to form the canopy.
Rules of Pruning
As a rule, Eucalyptus do not require much in the way of pruning, but if you want to carry out a little shaping and tidying, the process is straight forward. You observe the same rules as with other trees:
1. use sharp bypass-style secateurs, loppers and a sharp saw.
2. prune to maintain or develop a strong leader.
3. avoid weak branch angles.
4. cut just above a bud without leaving a snag.
5. avoid gouging into the trunk or a main branch.
6. always make a clean slanting cut without damaging the surrounding bark, preferably facing south, so it drys and heals quickly.
7. paint pruning cuts with a wound sealant (Arbrex Seal and Heal or Medo).
8. many Eucalyptus have thin bark, so sharp implements are important to avoid tearing and ripping.
Being a little hairy around the trunk is OK.
For the first two to three growing seasons, leave on the side branches emanating from the trunk. They are photosynthesising, feeding and building up the strength of the tissues and their premature removal will weaken the trunk. They also help to prevent the tree becoming top heavy, which can lead to wind-throw.
The species with a more multi-stemmed habit tend to be bushy, pushing out many lower side branches (also known as 'feathers' in young trees). If you are after a single stem tree then retain these, but nip out the ends, keeping two to three pairs of leaves. If a branch becomes wayward, prune it back again, but do not remove it completely.
With time, the tree will naturally shed them as it becomes more mature.
Dead branches could and should be pruned out avoiding leaving dead snags.
Once mature, wispy bits can be trimmed off to clean up the trunk with no worries.
The faster growing species tend to shed their branches very quickly and require little pruning.
A little and often is best when young
It is best to keep an eye on your young tree for a few years, shaping it and controlling its growth a little and often rather than leave it to mature and be forced into lopping off large limbs.
Eucalyptus respond well to pruning and if the young tree becomes top heavy as it matures (approximately years three to eight), you can remove large amounts of branchlets and foliage without much ill effect. This will slow it down a bit, giving time to strengthen the stem and allow the root system to catch up.
Once established and growing with gusto, a young tree responds to heavy pruning by generating a great deal of epicormic growth from the trunks and larger branches, these tend to be vertical shoots and may require thinning out. It is also why initial placing of any tree is important, because you don't want it growing straight up into telegraph wires or power cables.
As long as you stick to the basic rules of pruning (see above), a healthy Eucalyptus can be seriously pruned every three years or so, to keep it under control. Select from the shoots that sprout as re-growth and keep the best well placed ones to continue the tree canopy, thinning out and removing the rest. This can continue indefinitely for the life of the tree and means you can enjoy a well managed otherwise large species, in a controlled situation.
Unfortunately, if you have inherited a large tree, which is in need of remedial surgery, you will not have much choice other than to call in the arboriculturist (tree surgeon) to give it a serious prune. However, this can lead to the ingress of disease and shorten the life of the tree. Large cuts (anything over 1 cm diameter) should be treated with a pruning compound to protect against infections. I have seen very large Eucalyptus that have been heavily pruned, re-sprout vigorously. They do look butchered initially, but given a few years growth, they do attain a degree of elegance, but not what they were. Far better to select the right species and prune from the beginning (as you would a Apple or Pear tree)
Time of year
The optimum time of year for pruning Eucalyptus, in the U.K. is between April and September. Pruning after late summer means that the wound will have insufficient time to heal prior to cold winter weather. Frost can attack the pruning wound resulting in the bark peeling away from the trunk and may even kill the whole tree. Timing is not so critical in counties where frost is not an issue.
Grow without a stake
After planting your tree, try to grow it only with a short stake to secure the root-plate in the ground, whilst establishing. Remove the stake after a couple of years.
Why and How to Coppice Eucalyptus
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 :
1. rejuvenate old shrubs that have become leggy or lack vigour
2. renovate an old hedge that is used to being hard pruned such as Beech, Hornbeam or Yew
3. control the vigour of large trees and shrubs
4. produce a multi-stemmed tree or shrub
5. produce a crop such as Ash for firewood, Hazel stems for bean sticks, Willow for biomass and charcoal
6. encourage young ornamental juvenile stem growth in Dogwoods (Cornus sibirica 'Westonbirt') and Willows such as Salix acutifolia 'Blue Streak'
7. 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:
1. To control growth so that a large tree can be grown and enjoyed as a shrub
2. 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
3. To produce juvenile cut foliage for flower arranging either in your own garden or as a commercial crop
4. 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.
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 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.
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).
1. 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.
2. Remove all side shoots.
3. 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.
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)
1. 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.
2. Remove ALL side shoots.
3. 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.
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. gunnii divaricata
E. pulverulenta 'Baby Blue'
E. risdonii in sheltered areas
Avoid the following species for foliage production as they have poor coppicing ability:
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
Pruning for windy locations
In this section you will find information on the following:
Pruning system for windy locations
It is assumed by now that you have selected the right species of Eucalyptus for your windy location and have arrived at the point of wanting to prune it, to keep it happy.
One suggestion to aid firm establishment and reduce socketing, is to prune off approximately half the current seasons growth in late summer-early autumn (August-September time, prior to the gales) for up to three consecutive years (see hedge pruning). Avoid pruning late autumn, as frosts could damage the wounds.
Alternatively, every couple of years, you could elect to coppice your young tree by cutting it back hard to around 300-400 mm tall, at around Easter time. This action encourages the tree to build up a very robust thick trunk. The ensuing bushy growth could then be thinned out later in the summer if required. Once a firm set of roots has established after a few years of pruning, you could allow the tree to grow up without further pruning, although in very windy situations an annual hair-cut might be prudent!
Both of the above pruning systems reduce the tree's resistance to the wind (resistance put up by the lush foliage) and further reduces the risk of the tree being rocked around violently, damaging the root system (or worse, the tree being blown over). Now this may seem to be a rather drastic approach, but it is vitally important for the long term health and stability of the tree, when grown in windy locations.
One school of thought (which we do not promote) to prevent Eucalyptus from falling over in windy locations is to 'grow them hard' as they do in Australia. To ensure the tree does not produce lush top growth: don't mulch, do allow grass competition around the trunk, don't water in dry weather. The problem with this approach is that the young tree could fail to establish at all or in the worst case scenario, you could simply kill the tree! We think plant small and keep it pruned is the best approach when growing in windy locations
If you are yet to purchase your Eucalyptus, make your selection from our list of wind tolerant species and pruning back will not damage the appearance of your mature tree, but it could help it establish properly and survive.
What is Windthrow?
Windthrow occurs when a top heavy Eucalyptus, with a small rootball is planted, particularly in an exposed location. Sometimes it even happens with smaller stock. It often occurs under stormy conditions in poorly drained ground, such as a boggy clay soils. This is why it is important to select the right species for your location and if the site is known to be prone to strong winds, plant a small grade of tree from the outset.
See also notes on Choosing where to plant - Exposed and windy growing conditions
Overcoming Socketing and Windthrow
If you possess a young Eucalyptus that has been thrashed around by the wind and it is now flopping around at an unattractive angle (i.e. suffering from windthrow), do not be tempted to secure it to a tree stake; this is the worst possible thing to do. Strapping the tree to a straight piece of wood is like tying someone up in a straight jacket; over time the 'muscles' weaken. Eucalyptus need to gently sway in the breeze to strengthen their trunks.
Having said that, you need to gently tie the tree (using a soft tree belt or broad fabric strap that will not cut into the bark) in as upright a position as possible, to a substantial object. This could be a fence post, remote stake etc. a metre or so away from the Eucalyptus, such that the tree can still move and flex with the breeze. Alternatively, three guy ropes held in place with short ground stakes and secured to the tree using soft tree belts will support the tree and still allow it to sway.
You will also need to check that the root ball is firm in the ground; it may need gently firming down with your feet and the application of a thick mulch of bark chips. At the same time, it will be necessary to reduce the tree canopy by pruning out some of the branches and lightening the crown. It is important to carry out this pruning in a balance way so the tree does not take on a lop-sided appearance.
In cases where mature trees have been windthrown to the point where the root plate has been up-ended and the tree is now resting at a peculiar angle; our advice is to have it professionally felled by a tree surgeon and have the stump ground out. It is unfortunate, but either the tree was the victim of unusually strong gales, as many species of tree can be or it was the wrong species of Eucalyptus for that location - better to start again with a more robust species.
How to grow Eucalyptus as Hedges and Screens
What we mean by a Eucalyptus Hedge
The more bushy forms of Eucalyptus lend themselves to being pruned and trained as loose hedges. Not so much in the traditional sense of a square, tightly clipped Box or Yew hedge, but more as a linear, shrubby hedge, as you would find with Photinia or Pittosporum.
This is a practical way of managing these trees. You have the benefits of their robust evergreen foliage, in a range of silvery blue or green colours, with their wonderful fruity or spicy aromas (depending on the species). The 'hedge group of species' respond very well to pruning, to keep them under control; both shearing and coppicing work well. They can be comfortably managed at around 2 to 3 metres tall (approx. 6-10ft).
What we mean by a Eucalyptus Screen
This is where a single species or a couple of different species are planted to work together. They will form an evergreen screen of anything from 2 metres up to 4 metres tall (approximately 6 to 15ft) depending on which species are selected, what is required of them and how they are managed. They are planted either in a linear fashion to make a loose hedge or, where space allows, in a group like a copse or mini plantation, which may be used to visually block out a distant building or blot on the landscape.
Species to choose
Small leaved species which respond well to both clipping, shearing and coppicing are best. Also species which tend to have a bushy habit and keep their lower branches are good. However, please bear in mind that a Eucalyptus hedge cannot easily be maintained at 1.0 - 1.5 m (3-5 ft) tall as they will open up a little at ground level; it is the nature of the plant.
Choice of species for a fast screen:
Creating a Copse or small Plantation
Eucalyptus make excellent cover for game birds and wild life.
To achieve a small copse to provide a wild life habitat (or simply just for fun), combine a mix of fast growing and moderate slower growing species and under plant with shade tolerate shrubs, such as Aucuba japonica, Viburnum davidii, Mahonia aquifolium.
Plant the Eucalyptus at a spacing of 3.0 - 4.6 metres (10-15ft). Do not be tempted into planting at a higher density. If you plant the trees too close together, they will compete for light and become tall and narrow with high crowns. Bushy Eucalyptus species will be less bushy when planted close together. Further, close spacing combined with their natural tendency for rapid growth will result in the trees being floppy. They may lean and the trunks will not be as sturdy as they should. Counter this by pruning the leaders down, in April, by up to half the height, to a thicker shoot. This will help improve stability and allow the roots to catch up with the shoots, making more robust trees. To maintain a healthy copse, the trees should be cut down to just above ground level every 5 to 10 years in April. Cut down a few trees each year to maintain your visual cover.
Water, Mulch and Feed Mantra
During periods of dry weather, water your hedge or screen during its formative years. Once established it should not require watering.
Continue with the mulch to keep the roots happy
Feed your hedge or screen during the growing season as you would any other Eucalyptus.
See Care after planting.
A high potassium feed in August will help increase the Eucalyptus resistance to cold winter weather.
A feed of Bonemeal in the autumn will build a healthy, robust root system.
Why and How to Pollard Eucalyptus Trees
General Notes on Pollarding
Generally the activity of pollarding is done to reduce the overall height of a tree or shrub to less than they would grow naturally. It is done once a tree has reached a considerable size. It has to be carried out every few years thereafter and may be on an annual basis, to keep the tree at the desired height.
Common tree species that undergo this technique are Willows, Lime, Oak, London Plane and Eucalyptus. In particular, it is used to rejuvenate Oaks of 300 years of age or more, that are showing die-back in the canopy. By reducing the crown, the root system is relieved of some of its work and the tree responds by producing new vigorous growth. As a result the whole tree becomes healthier in its twilight years.
It is a serious job, usually involving working at height and is best given to a tree surgeon to carry out. Very often, this is a case where one needs to choose the right tree for the location, prior to planting. However, pollarding is frequently carried out on mature neglected trees that a householder has inherited, as a result of acquiring a new property.
The process involves leaving the main trunk untouched and pruning off the crown of the tree leaving the main five or so branches. These are also reduced in length and after several weeks or so, new shoots emerge from the ends of the main branches and in the case of Eucalyptus, very often up the trunk too. The new shoots emerge from meristematic tissue just under the bark and are loosely secured to the old branch structure by callous tissue. The adhesions lignify and strengthen with the passage of time, as the tree lays down woody tissue.
Eventually with repeated pollarding sessions, the tree takes on the characteristic swollen head of a 'pollard' as seen in many town and city streets (think wind in the willows Salix trees).
Eucalyptus are pyrophytes; they have the ability to regenerate after forest fire. One of their survival adaptations is that they have a great deal of meristematic tissue lying dormant in their cambial layer, deep under the bark. Released from suppressive growth hormones in the shoot tips of branches, this tissue quickly develops epicormic shoots just below the pruning cut, a couple of months after pollarding. The leaves on these new shoots will pass through the juvenile stage very quickly (they may miss it out altogether), fly through the intermediate phase and reach adult foliage.
The new shoots soon re-establish a tree canopy with a network of branches, but very often one shoot will become dominant, suppressing the development of the other shoots. Pollarding can be a short term solution for a fast growing Eucalyptus species, but genetically they are geared towards the fast and furious end of the spectrum; more Hare than Tortoise.
With fast growing species, the tree will quickly grow away again and may need pollarding annually to be kept under control. Fast growing species that would undergo the practice would be:
E. dalrympleana, E. deanei, E. glaucescens, E. gunnii, E. nitens, E. obliqua, E. regnans, E. rubida and E. urnigera.
These species want to produce a very straight trunk, tend to drop their lower branches early on in life and so the crown of the tree rises up the trunk very quickly. Pollarding reduces the height of the crown again, forcing the tree to form branches lower down, just below the cut. The crown is the point at which the main branches begin to sprout from the trunk.
Age of tree at pollarding
The tree needs to be over two years old when first pollarded, otherwise it may not have enough energy stored to facilitate regeneration. Beyond eight to ten years when pollarded, Eucalypts will look a little challenging until they have re-grown branches with a substantial mount of foliage.
Technique and Timing
The best time of year is spring, from the middle of March onwards. Using a very sharp saw or loppers, prune off the trunk 1.8 to 3 metres (6-10ft) from the ground, with a sloping cut, (facing South, so the sun helps to heal the wound). Treat the cut with pruning compound. Leave any side branches and leaves on the tree; this encourages sap to rise up the trunk and feed the dormant buds.
We currently have no experience of the long term effects of annual pollarding on young Eucalyptus trees, but will be carrying out trials at our nursery.