THE AGE OF FRUIT TREES - Part 3

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The Life-Cycle of Survival

A young tree, seen in cross-section, looks regular and circular. There are three significant circular areas within. The inside is made up of vascular cells which deal with the transmission of water and nutrients within the tree. They are produced by a ring of rapidly growing cells, called the Cambium Layer or the Meristem, in the language of the cell biologist. The inside cells are constantly produced and each year they add a ring to the centre of the tree, reflecting growth followed by dormancy. These cells live for a while but as new rings are formed, the inner ones start to die. This dead material does no harm and adds strength to the tree. It becomes the wood that is harvested in some species.

 
 
 
 
 

 

The surrounding Cambium Layer can be viewed as the engine of the tree and the cells here are akin to stem cells. They can differentiate themselves into cells that grow into buds or shoots, annual tree rings or bark. The bark is the outer layer that the Cambium Layer throws out for protection. Each year more bark is added, in the same way as tree rings but, unlike the tree rings, the older bark is on the outside.

While the Cambium Layer is alive and connected down the tree to the cambium layers in the roots, the tree will remain alive. The inner wood and the bark are not essential to life. We have seen trees where the centre has completely gone and 80% of the surrounding trunk is missing, with just a thin wall of cambium layer and a bit of flaky bark remaining.

 

 

Each year the young tree grows and stays circular. If it stays healthy, well-tended and accident-free (though there are many reasons why a tree can be tipped into a different growth mode, such as abnormal weather, lightning, animals and competition) it will probably continue to grow evenly. In these cases, with plenty of examples still to be seen, it might reach an age where it stops growing, now sufficient for its survival needs, and yet still be fairly circular in section. As it slows its growing and stops, the tree rings become closer and the bark starts to become weathered. Sections from old trees clearly show the tendency to grow less each year.

The reason tree bark looks the way it does is simply because the outer growth is that from earlier years when the tree had a lesser circumference. As the circumference grows the inner growing bark is wider and pushes out the narrower outer bark, causing it to fissure. When the bark stops growing, wind and rain, perhaps helped by insects and woodpeckers, erode the outer bark and gradually the fissuring becomes less evident and shallower. For a tree that ceased to grow many years ago, the bark can become scaly and very much smoother. This cannot reliably date a tree, because trees stop growing at different ages and weather factors vary from site to site, but a smooth bark is a sure sign of significant age.

Whether or not it goes hollow, such a round, post-growth-phase tree is undoubtedly capable of a long life thereafter, barring any accidents. Even when hollow, the cylinder still maintains great strength. It might also be capable of growing again, if the need should arise.

In other cases, in growing trees, the trunk reaches a point where something provokes it into uneven growth. The photo of the apple tree section on the previous page shows that some points in the circumference have grown relatively slowly, or even not at all, while at other points the growth has continued, perhaps accelerated, producing a fluting at the slow growth lines and pillars at the fast growth lines. In time, these pillars can round themselves off to produce the conductus or conducti that are visible in the Milton Wonder and the Appleford Serendipity. The use of the word conductus is our own, in this scenario, since it conveys not only a shape but a function, as the carrier of sap when the rest of the trunk is incapable. What causes a tree to leave regular concentric growth is not known. It might just be within the genetics of some trees, but is more likely to have some environmental cause.

The Dorton tree (see photo on previous page) is clearly old and appears healthy, yet it has a remarkable trunk, continuous with fledgling conducti. It shows signs that it might be hollow and perhaps hollowness/inner rot are the triggers for the rapid growth of the convolutions, though tree sections show that convolution is still possible in solid trunks.

At some point in the rounding process, the cambium layer grows much faster at the edges and curves its growth to begin the formation of a new circular stem. This is clearly seen in the photos of the Appleford Serendipity (previous page). The normal cambium layer, encountering a break in itself, would grow until it rejoined the remainder of itself. If a stem/trunk is incised vertically, deep enough to go through the whole of the cambium layer, both sides of the cambium will usually grow back together again. This is the case in wounded trees, provided the cambium layer has an intact inner core and template to grow against. If that trunk core is missing or rotting, then the cambium growth is not restrained to a particular path and can grow in its (perhaps natural) way, along a curve, until it encounters itself and joins up.

In the case of Milton Wonder something different has happened. A piece of cambium has encountered decay on either side and the core of the trunk has gone. The bark is falling from the outside. This piece of cambium has the misfortune to be rather narrow, but has the good fortune to be firmly connected to the roots. It falls away from the trunk (inside) and gets on with the business of re-growing. Either it grows from the inside out, or the route to rejoin itself is short. It is probably the former, given its size. Nevertheless, it is rounded, growing and producing a thin bark. It will become a new tree in time. Being akin to stem cells it differentiates itself into whatever is needed, and that would be hard wired from the DNA and its switches. This tree has been a remarkable find.

In both of these significant trees, and in the others which are part way along the process, the powers of re-generation are now evident and so very important. In much the same way, trees which fall and re-root/re-shoot in moist soil are adapting to circumstances in a way that allows them to continue existence. Fruit trees, and particularly apple trees, have the capacity to retain moisture and vitality in their cells, long after other trees would be stone dead. They also appear to have a strong capacity to live off air moisture, when disconnected from their roots, long enough to avail themselves of the opportunity to send out new roots if conditions are auspicious. We once took scions from the extremities of a tree that had been at least two years out of the ground and with no living material in contact with the ground, from which to root. The cuttings were successfully grafted.

Never write off a fruit tree. They can do astonishing things. In other hands than their caring owners, both the Milton Wonder and Appleford Serendipity would probably have disappeared many years ago. We are sure that both Mrs Marlow and the Brices would concur that there is a vital and very rewarding symbiosis between such trees and those who care for them.

Conclusions
(-and we think they are rather important ones)

Lawson, when reflecting upon the potential age of fruit trees, made the distinction between trees that suffered harm through accident or poor husbandry and those that had a good life, free of harm. For the latter he proposed three phases of life, of roughly equal duration; one each for growing, standing still and decaying, as with most animals on the planet. Observations suggest he was right, as far as it goes. To suggest 300 years for each phase might seem excessive, but might also be close to the truth. It remains to be seen - but not in our lifetime. No other writers have turned their attention to how fruit trees can cheat the ultimate third phase and re-grow from decay (though Forsyth made some observations on extending life).

We all know that the single-celled Amoeba can divide interminably and preserve itself forever– but as a separate entity. In the higher life forms, the possibility does not seem to have been considered. The natural philosophers might enquire into the lifespan of man or trees, but did not appear to think the unthinkable. Nevertheless, there is no escaping it! Fruit trees (well- apple and pear trees, at least) are theoretically capable of living forever as one indivisible corpus. This is quite momentous, when travelling on to consider just how many really ancient fruit trees we still have with us.

In our article on Identification on this website we have already covered much on the subject but, statistically speaking, we might easily still have living trees (and certainly varieties) that go back a thousand years. As we said, before, “In extremis two grafts might be all that is needed to keep a 900 year old variety alive today. Three grafts could keep extant a variety that existed in the dark ages – one graft for a tree from the French revolution or four grafts for a tree planted just after the Romans left”. A tree could fall over several times, or re-grow while standing. That old tree in your garden or unexpected on some divorced piece of land could be older than Westminster Abbey.

Our old fruit trees have seen too much history to deserve casual removal for the sake of 'the latest thing'. They rank along with ancient monuments in their importance and need our protection. They are not getting it. If we tampered with a grade 1 listed building, the penalties would be severe, yet we can destroy an even older, more unique, living thing with impunity. They have no real protection in law, despite the availability of tree protection orders, which are never used for fruit trees. Conservation Areas should protect them, but the practice and the theory are very different. This must change. An old tree properly cared for will fruit very well, and is a positive enhancement for property values. They look and feel good, even if decayed, leaning, flat, hollow or split. They might also be the last of their type. All they need is understanding and time to renew themselves. Becoming aware of their possible age and endurance makes it more likely we will value them and keep them. Alas, our work with old trees is littered with examples where a tree seemed safe but disappeared within a few years.

From 1947 to the 1980s the Ministry of Agriculture, Fisheries and Food promoted the view that fruit trees were not worth keeping after 30-40 years of productive life, through a series of bulletins to the growers and the public. How many old trees were lost? This ethos has proved itself quite enduring and is still commonly believed. DEFRA, the successor to MAFF, maintains the tradition with its soul-less disinclination to feel the sense of history and mystery. They want to keep trees - until a proposal turns up to cover them with concrete, tarmac or an HS2, in the name of ‘economic growth’. Make a fuss if you can, but meanwhile we will get back to the point.

It is simply this – old fruit trees are magical and can live forever if we treat them well. They are steeped in folklore and the annual practice of wassailing them, to appease the spirits within and promote vitality, is but one example. Get to know them, befriend them and defend them -and please tell us if you know of a significantly old or interesting tree. There is always more to learn.

Derek and Judy Tolman, 6th May 2012