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Posts tagged ‘pruning’

Time to prune your walnut trees

July 15, 2014

Gabriel Hemery

walnut wound early occlusion

walnut wound occlusion following pruning in July the year before

Remember to prune your walnut trees at this time of year. Traditionally walnut trees are best pruned on or around St. Swithin’s day. Read more

For more about growing walnuts for fruit production – see here

Prune your walnut trees on Saint Swithin’s day

July 15, 2011

Gabriel Hemery

Saint Swithin window at York cathedral

Saint Swithin window at York cathedral

It is Saint Swithin’s Day today, 15th July: the day on which people traditionally watch the weather.  Tradition says that whatever the weather is like on St. Swithin’s Day, it will continue the same for the next forty days.

There is a well-known weather-rhyme in Britain:

St. Swithin’s day if thou dost rain
For forty days it will remain
St. Swithin’s day if thou be fair
For forty days ’twill rain nae mair.

St. Swithin’s Day is also the ideal time of the year to prune walnut trees.  Pruning walnut trees in the dormant season (i.e. when the leaves are absent) is not recommended as it is for nearly all other broadleaved tree species.  If a walnut is pruned when the tree is dormant, or even worse when it is actively growing, the pruned wound will bleed profusely which will weaken growth the following season, and possibly increase risk of infection.  Pruning is undertaken ideally near the end of the walnut’s active growing season and St. Swithin’s Day, in mid July, provides a perfect marker.

Gabriel Hemery

Phenology and frost

April 11, 2011

Gabriel Hemery

It has been the warmest Spring for 60 years in the UK but it’s the time of year again when most gardeners will be watching out for a late Spring frost, hoping that they can protect their tender plants.  Horticulturists are well aware of the terrible financial impact of frost on the flowering of apples and pears, where a whole year’s potential crop can be killed off.  In forestry we’ve taken longer to get serious about frost.

Study of the timing of events in plants is known as phenology.  For several years I undertook research into the flushing (the phenology of spring leaf burst) for two of our most sensitive tree species: ash Fraxinus excelsior and common walnut Juglans regia.

Unlike the plants in a garden that can be moved to a greenhouse or protected with fleece material, the trees in a forest cannot be protected so immediately.  However the forester is not powerless.  There are practical silvicultural steps that can be taken to match carefully a species to its site; such as altitude, aspect, and micro features (e.g. avoiding frost hollows).  Perhaps the greatest potential advantage can be realised through genetic selection: using planting stock that have been selected to be late flushing – reducing the likelihood of frost damage as their buds will break later in the Spring.

walnut phenology

Walnut phenology and a flushing score

I made these drawings to illustrate scientific scoring systems that I had developed for use in the field to assess the phenological development of different trees (progenies or provenances)  in trials.

ash phenology

Ash phenology and a flushing score

Foresters have ignored phenology at great cost in the past.  Southern beech Nothofagus species were introduced to Britain in the 1950s with some excitement due to their fast growth and useful timber.  Field trials and some commercial plantations of roble beech and rauli beech looked promising for a number of years until several cold periods devastated hundreds of hectares.  Why?  The seed collectors for these plantations had gone to the wrong places in Chile to collect seed.  Had they considered better the phenological aspects, these promising species may by now have been more widely adopted.

Ignorance of phenology was also prevalent for several decades when the cheapest tree seed was sourced from Eastern Europe and imported into the UK.  These origins were often not appropriate for the UK and I have seen numerous plantations of ash with multiple forks, established during the 1980s and 1990s.  The impact is significant as these trees will never produce a valuable crop unless the owner repeatedly visits the trees to apply corrective pruning – and this costs time and money.

Gabriel Hemery

Pruning tools – my top choices

March 18, 2011

Gabriel Hemery

tree pruning tools

My own collection of well-used tree pruning tools: Bahco loppers, Silky Super Accel 21 folding pruning saw, and Felco #2 secateurs (and leather belt holster).

I have often been asked what tools I use for tree pruning; here’s my top personal choice of tools.

Go for the very best that you can afford.  I find that a combination of  by-pass secateurs, together with long-handled by-pass loppers and a top quality pruning saw, will tackle almost every job.  The only additional tool necessary may be a bow saw although if you need one it’s questionable whether you are technically pruning, rather coppicing, pollarding or felling!


I always try to work to the rule of thumb when pruning: prune no branches larger than your thumb.  This will minimise the time needed for the wound to heal (read more about pruning technique).  However, this requires you to keep on top of the pruning in your wood, orchard or garden, and inevitably there will be occasions when you come across a large branch that is too big for secateurs, and perhaps awkward to reach with a pruning saw.  This is where a good pair of loppers are a worthwhile addition to your pruning tools.

I use a pair of Bahco Expert bypass loppers which are immensely powerful and will cut easily through green wood over 25mm (1 inch).  There are other models in the range including those with telescopic handles.  Be careful not to twist the handles if you are tackling wood that may be too thick: this can twist the metal blades and damage the tree.  If it is getting too tough, you may need to switch to using a pruning saw.

Pruning saw

Pruning saws are designed for the task: having  aggressive cutting teeth for green wood, which are angled to work on the pull stroke.  This means that cutting branches that you need to stretch to reach is easy work.  Their rigid blades allow you to accurately control the cut so that you don’t tear the branch collar while allowing you to to get close enough to the stem.

Personally I swear by the fantastic quality pruning saws made by Silky Fox.  I have owned and used many models over the years; from tiny folding models to the extendable pruning pole saws that allow pruning up to 6m or more.  My favourite is probably the Silky Super Accel 21, which is small enough to fit in a pocket but will cut through 10-15cm fresh wood as if it was butter.  The blade has two open positions for dealing with high branches or those lower down.  Its rubber handle provides super grip and is welcome in the cold of winter when you are most likely to be out in the woods pruning.


If you are on top of your pruning regime, and keeping to the rule of thumb, a good pair of secateurs (pruning shears in the US) will be your most-used tool for formative pruning of young trees.  The Felco range are used widely by horticultural and forestry professionals and renowned for their quality.  The Felco – Model #2 is the standard model and one that I’ve used almost exclusively.  Most Felco models are available in both right and left-handed models.  Model #2 includes a notch for cutting wire which can be very handy.  I use a leather belt holster which is very useful when you may have other tools to carry around, and prevents you putting the secateurs down in the leaf litter where they have an uncanny habit of disappearing instantly.

Don’t forget to sterilise your pruning tools between trees, and between different sites (read more).

Gabriel Hemery

Tree wound occlusion

March 17, 2011

Gabriel Hemery

The ability of a tree to heal itself quickly following pruning is important as it reduces the risk of infection, reduces the impact on tree growth, and improves the quality of its timber.

I’ve written previously about how to prune a tree and if you follow these guidelines correctly, the tree will be able to repair the tissue around the pruning wound or occlude the wound.  Here are some pictures of walnut and cherry pruning wounds occluding, and the results when pruning is carried out incorrectly.

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Three wild cherry images share in common the fault that all the branches removed were large in size.  To make the situation worse, whoever pruned these managed to damage the tissue around the branch-bark ridge, probably by cutting too close to the top or side of the main stem.

Notice on one of the walnut images the hole in the centre of the former branch, as walnut has a chambered central pith – but that’s another story!

Gabriel Hemery

Sterilise your pruning tools

March 14, 2011

Gabriel Hemery

I co-authored a pruning leaflet about eight years ago which has been a popular guide for woodland owners, managers and others who care for trees (see previous post).  However, there was a serious omission in the leaflet that has prompted an update: the importance of sterilising tools between trees, and between sites to reduce the risk of spreading infection.

The importance of phytosanitary control is now paramount, with the apparent increase in serious outbreaks of pests and diseases affecting our trees, such as Phytophthora ramorum (Sudden Oak Death) [apologies for incorrectly stating Acute Oak Decline in a former draft].  Knowledge about the impact on disease spread from pruning has existed for over a century: in the USA Waite and Smith (1906) linked fire blight (Erwinia amylovora Burrill) infections in plant nurseries to contaminated pruning tools.  More recently Goodman and Hattingh (1988) reported a 66% infection rate in trees pruned with secateurs treated with bacterial spot (Xanthomonas campestris pv. pruni Smith), although interestingly infection rates were only this high during cool and wet conditions.  The worst case of infection spread will come from pruning weeping bacterial wounds, e.g. cankers, where extreme care should be taken to clean tools after use – better still, wait until the oozing has dried up before pruning.  There is some evidence that even the best cleaning methods are ineffective at removing bacteria from the surfaces of cutting tools (Kleinhempel et al. 1987).

pruning tools to steriliseThe following action is recommended on sites where there is a biosecurity problem but I would go further suggest that it is good practice to follow these recommendations at all times.

Sterilise pruning tools between use on each tree by wiping with a cloth soaked in industrial methylated spirits (IMS).  You should also complete a more thorough sterilisation between sites, by soaking your tools in IMS.

Some suggest using household bleach, perhaps diluted nine parts water to one part bleach.  However, be aware that bleach is extremely toxic to plants, will ruin your clothes if splashed or dripped onto them, and it is a corrosive that will also spoil your tools.

After a hard day’s work in the garden or woods, and following disinfecting your tools using IMS as recommended above, rub some vegetable oil over the metal parts to keep your pruning tools in perfect working order.

Gabriel Hemery

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