Management of lapsed and new pollards

Management of lapsed and new pollards, de Ted Green

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Cork oaks in Extramadura are an example of centuries old cultural tradition of cutting pollards.

There are also examples of ‘trasmuchos’ in the UK. These are now massive old lapsed pollards. Past term for this type of tree is – ‘compass’ tree. Compass means curved – trees planted and trained for future use for building of houses and ships.

There are still kilometres of these pollards or ‘trasmuchos’ in the Basque country. There were many different uses for the products from these trees down the centuries – one use taking over from the other as technology moved on. They were originally cut for the shaped limbs for building or ship building but then it became possible to bend wood under steam. So they cut the limbs to make charcoal to heat water for steam. Then they cut them for charcoal for iron/ steel production. Now they are valuable for their cultural heritage and biodiversity values.

Beech pollards could be shaped for a purpose. These ‘orchards’ of pollards are in Basque Spain – in Aiako Harria Natural Park south of San Sebastian. There are now concerns over regeneration of these trees, however it is important that we do not cut down trees to make gaps for regeneration. It is necessary to get regeneration around the outside of these areas.

In the UK we have very many, very old pollards that we now call ‘lapsed’ because it is a long time since they were last cut in rotation. The limbs on these trees are very large and our major concern is that trees collapse under their own weight. Hence the need to intervene to lighten the crown to prevent catastrophic collapse. We cannot afford to allow any of these trees to collapse in this way – we wish to see no further avoidable loss of ancient trees.

In the UK, originally we tried cutting ancient, lapsed, oak pollards back to the original cuts or ‘bolling’. However, the cutting of this size, age and diameter of branch resulted in killing many of the trees.
The same happened with old lapsed hornbeam (Carpinus).
Members of the Ancient Tree Forum started to meet at different sites to discuss why trees were dying and how they could be managed better.

This is the Ancient Tree Forum having a discussion under an ancient oak – I call this 50 brains working together to come up with good solutions.

There is so little written down about the tradition of pollarding and nothing about how to care for lapsed pollards. So we have to learn everything for ourselves. We also look at old paintings to see if we could learn about old techniques. This one is full of pollards and shreds in Romania. Each one of the trees in this picture has been cut for different products.

And we can look at old tapestries to see cut or pollarded trees.
We can even compare old drawings and paintings with the trees today. This example is comparing a drawing of 1815 with the same tree today. Remarkably this tree seems to have grown very little in nearly 200 years. These examples give us an insight into how ancient trees change over time.

A diagram showing the process of how trees grow and become ancient – the changes to the shape of the crown and due to hollowing. Shown from the side and in cross section of the trunk. Note the stag heading as the tree goes beyond the mature stage and a new crown is created lower down. Retaining dead and decaying wood in the crown is very important.

We looked in the countryside for examples of trees ‘growing downwards’ (crowns reducing in size/height) as they age and their responses to high winds which are frequent in the UK. Here is a stag – headed oak tree that has started to grow down. In this case the cause of the loss of the upper crown is probably due to a long drought.
A natural example of a tree recovering from the impact of a very high wind. One part of the old crown remains and a second very vigorous crown is developing on the other side.

In this case all the major limbs except one of the tree were reduced by a high wind. The tree has responded by creating a perfect new crown. This sort of example gave people the idea to try ripping limbs or break out limbs to naturally mimic crown reduction by wind. An open grown beech that hasn’t responded as well as all the previous oak trees. This made us consider the responses of different species of tree to wind and the aging process.

We are still unable to explain how trees respond to leaf fall in autumn. In the case of this mature beech tree, it has developed two ‘crowns’ – the top one has lost all its leaves already. Can this help us decide where to cut trees when we want to reduce them as naturally as possible?

Even younger trees such as this hornbeam (Carpinus) may produce two crowns in some circumstances.
The following sequence of pictures shows recommended practice in tree management in the UK. In this case a mature oak has had its crown reduced by approximately 2-3m, reducing wind resistance very significantly. Look at the size of the diameter of the cuts limbs – the cut ends are less than 15cms which is important in the first phase of cutting on some species.

This is the response of the tree a few years later – in summer. Note that there has been very good regrowth, particularly lower down on the limbs and trunk. At this stage the tree could be considered for further reduction as the living wood all the way down the tree to the roots is being kept working.

The same tree in winter – showing response. Because of the significant response at the end of the limbs, further intervention will be necessary before this re-growth shades out lower growth and makes the limb vulnerable to wind again.

In high use, urban areas, crown management may save trees. These two oaks were threatened with complete felling and removal but tree work meant they could be retained.

Ancient beech pollard that has had the first phase of tree retrenchment pruning, however in the case of poplars the first restoration cutting could be lower down. Each tree because of its species, age, condition and location needs to be treated individually.
Two Examples of crown reduction of old, hollow elms near Madrid. Parallel thought in tree management by two nations.

In the same town. We use this as an example to many arborists in the UK. It shows crown reduction so that an important hollow tree can be retained in a very public place.

Behind the statue of Queen Elizabeth II are 250 year old Tilia that were reduced by two metres so that they could be retained.
Tree surgeons undertaking phase 1 retrenchment cutting of the crown of an old oak pollard. They are cutting with hand tools half way through small branches and tearing off the remainder to mimic natural pruning by wind.

Beaver coppicing. Beavers evolved with coppice. They leave stub ends and sap risers. We should mimic their methods when coppicing or we increase the risk of the coppice failing. The right hand coppice stool is a good example of leaving sap risers – in other words not taking all the stems at one time.

This diagram from a French research study shows the location of starch storage when a tree is cut. The darker the shading the higher the starch reserves. It supports the reason why beavers leave stub ends – because the starch is stored near to the cut ends ready for utilisation in spring growth.

Restoration cutting of an old, pollard hornbeam (carpinus) pollard. Stub ends have been left and sap risers. Where limbs are less than 15cms in diameter leave stub ends that are 6 x the diameter of the limb being cut. Hornbeam is one of the species of tree that usually responds successfully to cutting so in theory can be reduced further than other species at the first retrenchment cut. However trees must have sufficient light around them in order to respond effectively.

Two illustrations of an ash that has been cut in Spain on a regular, short rotation by axe. Where cutting is done by axe on a very regular basis and no lapse in the cycle, the trees appear to live very long lives – longer perhaps than maiden trees. Close up of the cutting which was done by axe.

Traditional, 60 year rotation cutting of beech pollards in Leitza, Navarra by a local woodsman. In the Basque mountains, the climate is cool and the rainfall is very high. Presumably these conditions allow the cutting of larger limbs. This degree of cutting in the east of England would kill similar trees because of the low rainfall.

A series of illustrations of Black Poplar pollards that have been cut leaving sap risers. It was in this region, 30 years ago, that the Ancient Tree Forum saw this practice for the first time. Sap risers and abundant re-growth on an old pollard.

Black poplar in the Sierra Guadarama where the practice of leaving sap risers on old trees was first seen in the 1970’s.

Trees that produce wispy epicormic (shoots) growth, like on these old beech trees on very old common land, are more likely to respond to cutting. Man may have recognised such trees that could be cut and grow again readily and successfully for long term cropping.
Whiskery beech on an old iron age, hill top fort – maybe the practice of cutting has been perpetuated down the centuries.

Shading by ivy or other creepers or moss, can prevent the shooting of dormant or adventitious buds on pollards after cutting and can lead to the death of the tree.

The living sap wood rings of this tree have recently died after cutting and are being decayed by endophytic (dormant inside the living wood) fungi that are activated once the wood has become dysfunctional.
A column of dysfunctional wood created by the cutting of a very large old limb on this ancient beech pollard is being decayed by an endophytic fungus.

Comparison of two limbs on the same tree following different types of cutting. Sap risers keep the living columns in the sapwood working to the benefit of new growth in the crown and root system.

The growth on the right hand side has new branches that are knitted into the stem and will not break out easily. By contrast the new branches on the hollow stem on the left have no support from the thin ring of sapwood. The left hand limb is of such an age and diameter that it may have too little living sapwood to provide the strength to support regrowth and cannot form a bolling.

If we are starting new pollards, is this the age at which to make the first cut and just above the stem that retains its leaves?
In the UK we are learning about starting new pollards. We believe that they should be when the trunk and limbs are less than 4cm diameter and to the form of the tree.

The second cut above the bolling on a young ash pollard to continue the rotation. On this occasion the limbs below the bolling are also removed to prevent competition.

Second cut immediately after cutting. Leaving stub ends, mimicking what we have learnt from Spain.

Close up of regrowth after third rotation cut. Regrowth has been successful all round the cut stubs and all the new growth has knitted in well into the stem.

All nations have thousands of kilometres of autoroutes that have been ‘landscaped’ and planted with trees and shrubs. We say ‘trees with no future’ because when they reach a certain size they are cut down. We believe there is a great opportunity to cut the trees to produce the different, local forms of age-old, cultural traditional practice and provide some sustainable products at the same time.
Prince Charles starting new willow pollards. If we are able to inspire our future king to cut his trees in this traditional way, let us hope we can persuade others across Europe to help preserve part of Europe’s cultural heritage.

It took 9 members of the Ancient Tree Forum with outstretched arms to encircle the trunk of the Bowthorpe Oak – one of the oldest oaks on the planet. The ATF is a group of people from many walks of life that are passionate about old trees and the part they play in our cultural history. Come and join us!
Interview on Spanish TV.

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