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Pruning Guides for Eucalyptus

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Pruning your Eucalyptus, at the right time of year, is essential for you to achieve your goal of a well-behaved screening tree or bushy shrub

Why prune?

You don’t need to prune a Eucalyptus if it is to be grown to its full potential height and where it has the space so to do. Eucalyptus gunnii in a rural field doesn’t need pruning. Eucalyptus gunnii in an urban back garden definitely requires pruning to prevent it from achieving an 80 feet tall tree with a trunk some 3 feet in diameter. That’s 25m x 1m in new money! This is the same thinking as taking a yew tree and pruning it as a hedge or a massive beech tree and training it as a piece of topiary. Eucalyptus can be trained into many forms: a hedge screen, shrub-on-a-stick (lollipop or small tree shape), bushy garden shrub.

When?

Timing is everything, in many ways. The short answer is National Eucalyptus Day March 18th followed by the Chelsea Chop at the end of May AND every year, if you are looking for total control. March 18th or thereabouts is ideal for structural pruning; pollarding etc. If the weather is frosty or rainy or snowy, delay the pruning until it is slightly warmer and dry.

Chelsea Chop is more of a Chelsea Shave with Eucalypts. You can tip prune young trees and shrubs and removing up to as much as 90% of the new growth produced since March, but don’t cut them hard back into the old wood this late in the season. Tip pruning, trimming off a couple of centimetres, can still be carried out in June and into July if you need to keep very tidy.

Eucalypts only heal when the sap is rising in the Spring. Large open pruning wounds can leave them at risk of catching the fatal Silver Leaf Fungus, Chondrostereum purpureum. Always treat pruning wounds of 1cm and larger with wound paint. If you want to try killing a Euc – prune it hard in November!! It may take a few years, but you will be successful.

Miss a year’s pruning date and you will have allowed your tree to build extra root collateral to throw out more growth year on year. More foliage up top = more food factory returning carbohydrates to be stored and build the root system = bigger root system to throw out even more growth next year. Even though you prune hard the following year, you have still allowed your Eucalyptus to build bigger real-estate below ground. This is why it is so hard to tame a 12m tall monster down to a passive 3m shrub-on-stick. That ship has sailed my friend! Start as you mean to go on; if you want to keep your Euc small and bushy, prune every spring as a minimum.

Why do Flower Farmers prune in the autumn and winter? Well, that is when they want to take their harvest. They knowingly run the risk of losing a few cropping bushes every year. Its just the nature of the business.

After hard pruning in Spring, your Euc may sit twiddling its thumbs for a good couple of months before throwing out new growth, so please be patient. It needs time, warmth and a degree of understanding from you!

What?

What equipment will you need? Sterilised sharp secateurs or loppers, we also use wood saws as they give a fine cut. Pruning wound paint such as Prune & Seal by Growing Success. Sterilise your pruning kit by cleaning in hot soapy water and sterilising using raw alcohol or cheap vodka. Long reach pruners are great for taller shrubs and small trees. If you need a ladder, this will require you to do sensible things like having a responsible adult present to shout at you – Please be careful!

If you own a large tree where you are pollarding on a 3 or 5 yearly cycle – you will need a specialist piece of equipment called a ‘fully qualified tree surgeon who knows what they are doing’! Make sure you book a March appointment.

How?

How to prune: avoid cutting back into the trunk where possible. This is counter intuitive to pruning say an apple tree, but with a Euc, leave a short snag. It’s a smaller pruning wound and there is less risk of diseases getting into the main trunk and running riot through the rest of your tree.

Use a slanting cut to drain sap and rain away from the wound, and facing south so the sun helps the healing process.

For pruning ‘style’ – we hope the following cartoon sketches help illustrate what you need to do.

If you want bushy, remember the following mantra.

MANTRA: Broad bottom, narrow shoulders and a flat head

Not a good look on a human, but what every bushy Eucalypt is wearing this season!

Here are 7 different ways to prune your Eucalyptus tree.

1) Growing a ‘Standard’ Eucalyptus:

If you want to let your tree reach for the skies and reach is potential, the only pruning you may need to do it check for a competing leader and prune it back.

This is how you prune back a Eucalyptus of almost any age to produce or maintain a ‘standard’ tree shape. A ‘standard’ tree with a single stem and a fluffy top, where you will allow the branches to grow taller year-on-year. Treat young trees with care – you don’t want to remove too many lower branches whilst they are very young and spindly as this removes too many leaves for photosynthesis i.e. you starve them!

2) Producing a bushy ‘shrub on a stick’

This technique allows you to control the overall height of your tree. Bringing in the sides as well as the top encourages bushy regrowth all over. Removing the lower branches (called ‘crown raising’ or creating a ‘clear stem’) neatens up the tree and encourages top-growth. You might get some opinionated sprouting lower down the stem – remove these with care throughout the year.

N.B. if you are growing a screening tree for privacy, remember that it is always open and see-through where the crown (handful of main structural branches) begins at the top of the single trunk. To avoid looking through a twiggy gap at the top of your fence panel, ensure that you start the crown low down. You can always crown raise at a later date by pruning off lower branches. Its the devil’s own job to crown reduce a Euc if the crown is too high – you will have to prune off the entire head by pollarding down to around 30 to 50cm below where you want the crown to start.

3) Pollarding a mature or semi-mature Eucalyptus

Pollarding means to remove pretty much all of the existing growth on a mature or semi-mature tree. Picture an avenue of Lime trees just after the Council has chopped off all their branches – that’s the effect you’re going for! This bold pruning method is useful for gardeners who want to bring down the height of the foliage and is perfect if you wish to maintain a tree at a certain height with shrubby growth down most of the stem. If you’re looking for shrubby regrowth all over, we find this method works best when you pollard the tree into the ‘magic zone’ – ground zero up to around 1.2m (4ft). If you pollard a very tall tree and leave the main trunk taller than 6ft, you will only encourage regrowth towards the top of the stem – this is ideal for those wanting to create a tall ‘shrub on a stick’.

4) Coppicing a Eucalyptus down to ground level (to produce a multi-stem)

A bold and quite frankly scary manoeuvre! Ideal for those looking to grow a multi-stem Eucalyptus. This may be for firewood production, or to start growing an ornamental multi-stem as seen in image no.5. This is where ages and girth matter! Please don’t attempt this activity if your tree is less than around 5 inches (125mm) in diameter at the base – it will very likely kill it. Younger trees and those that have been through this ritual before, respond better than say a 15 year old tree at its first rodeo. The 15 year old may not appreciate being sawn off at the ankles for the first time in its life and may well simply give up the ghost. It will be an ex-Eucalyptus tree! Slanting cut, in Spring, facing south. Taking a firewood harvest may have to happen in February, before the roots push sap up into the trunk and make the timber too wet and heavy.