All posts from

May 2007

Tricotyledonous sycamore: first true leaves

Below is a photo of my tricotyledonous sycamore (taken by my father on Saturday), 23 days after I discovered it. Its first true leaves are now developing, and I am glad to see that there are three of them. As the tree develops, growth (branches, leaves and so on) will be trifurcate (in threes), as opposed to normal dichotomous (in twos) growth. Basically, this tricotyledonous sycamore is to a normal dicotyledonous sycamore what a four-leafed clover is to a normal three-leaved clover (Trifolium repens). I am interested to see whether or not its offspring will be tricotyledonous, although it's going to be quite a wait to find out.

tricotyledonous sycamore seedling with first true leaves – 28th April 2007

Posted in Miscellany

A walk on Blackford Hill (27th April 2007)

horse chestnut inflorescence

Close-up of a horse chestnut (Aesculus hippocastanum) inflorescence.

gorse flowers

Vivid gorse (Ulex europaeus) flowers. I know gorse isn't technically a tree, but it can grow fairly big, woody trunks!

elm leaves

Some species of elm of which I am not quite sure - probably wych elm (Ulmus glabra.

elm bark

The bark of a close-by elm of the same species growing on a rocky substrate. Quite a big one; must have avoided Dutch elm disease.

Posted in Gone for a walk

Branch shedding in mature beech trees

I recently recieved an email with the following photograph of an old beech (Fagus sylvatica) attached.

beech near Burwash, E. Sussex (Tim Symonds)

The sender, Tim Symonds, included the following information:

The beech in the attached photo is near Burwash, East Sussex. It displays clearly how the beech can drop its branches if need be. This one is in clay soil, on a steep-ish slope, about thirty metres above a tiny brook. The Woodland Trust guessed it must be between 200 and 250 years old. It is 220 inches in girth at 5 feet.

A girth of 18 feet 4 inches (559 cm) would give the beech a diameter of appox. 178 cm (5 feet 10 inches)! This is much larger than the Loch Tay 'Mother Beech' which had a girth of 377 cm (12 feet 4 inches) and thus a diameter of approx. 120 cm (3 feet 11 inches).

But I digress, and let us get back to the beech in the photograph. Why would a tree want to lose its branches? It might seem like a ridiculous thing to do, considering the time and effort invested in growing them. Yet many biotic and abiotic stresses (e.g. water shortage or disease) may cause a tree to shed branches. However, given the size of this specimen, it is likely that simple old age is the causal factor - senescence. I believe the following article describes the whys and wherefores of geriatric branch shedding particularly well. I will reproduce it here in its entirety, but I found it here (FindArticles). The author is Peter Thomas (a lecturer in environmental science at Keele University (UK)), and the article originally appeared in the May 2002 edition of Natural History magazine.

To live long, a tree must stay small.

Old age is not the problem for plants that it is for animals. Being modular, plants can grow new limbs when old ones die off. More crucial to the longevity of a tree is its size. A tree reaches a stage when it cannot get taller, owing mainly to the difficulties of bringing water up from the roots, and when its side branches cannot grow longer, because they are too expensive to support. So the number of leaves a tree holds becomes more or less fixed, and this means that the tree's ability to produce food--the sugar made in leaves by photosynthesis--also levels off.

Yet each year the tree adds a new layer of wood under the bark, and the amount of wood needed to coat the whole tree increases, just as, in a set of Russian dolls, each new doll on the outside has to be bigger. As the tree grows, the amount of food needed for running it rises. The tree resembles a bank account whose income (sugary food) is fixed but whose outgo (respiration and new wood) keeps mounting. The tree compensates for a time by producing narrower and narrower rings, but there comes a point when a ring cannot get any narrower. Something has to give, usually the water-deprived top most branches. The result is a stag-headed tree, so named for the antlerlike dead branches sticking out of the top. A downward spiral begins: the loss of branches means fewer leaves, and fewer leaves means less new wood.

But many trees can slow the process. Some have buds in the trunk that sprout new branches. These may hold enough leaves to make up for those lost higher up, so the tree can keep the leaf area constant while cutting out the expensive-to-maintain upper trunk and its big branches.

Although these new trunk branches are fairly short-lived (a hundred years in oak, sixty years in hornbeam and beech, and less in birch and willow), an oak with plentiful trunk buds can stave off death for centuries. As the old saying goes: "Oak takes 300 years to grow, 300 years it stays, 300 years it takes to decline." Perhaps we should think of a stag-headed oak as merely entering middle age and, like many humans, just going a little bald on top.

A tree has no fixed life span. To live long, it must stay small. One way to do this is to grow slowly. Bristlecone pines are the supreme example: they live on poor soil in a dry, cold environment with a short growing season. One bristlecone in the American Southwest has been documented at three feet tall, less than three inches in diameter, and 700 years old! The other way to stay small and live long is, paradoxically, to be cut down repeatedly. (This strategy, of course, will work only for trees capable of regrowing when cut.) The ash Fraxinus excelsior normally lives for 250 years, yet Suffolk, England, hosts a coppiced ash with a stump almost seventeen feet in diameter. It is at least a thousand years old.

A tree's bank balance is also influenced by savings in the form of food reserves. As a tree gets bigger, however, it has less food left over. At the same time, the larder--the sapwood--gets smaller. Eventually, infections penetrate inner structures, and storage capacity is lost behind a barrier zone, a layer of new cells produced in the inner bark to seal off infected wood. The living part of the tree is walled into a thinner and thinner space under the bark. Part of the tree dies. New branches on the trunk can still save its life, but a large old tree is not good at producing new shoots, perhaps because it is running out of stored buds or because they are trapped behind thick bark. New sprouts on weak trees often die just when people think the tree is going to live. This may be because the barrier zone is missing or because there are too few reserves left for the tree to grow a strip of tissue from the new branch down to the roots. Either way, disease easily overtakes the tree, and the branch withers away. At this point, the tired old tree bows out gracefully.

COPYRIGHT 2000 American Museum of
Natural History
COPYRIGHT 2003 Gale Group

Posted in Miscellany

Wild cherry and gorse (30th April 2007)

wild cherry flowers

Wild cherry (a.k.a. gean) (Prunus avium) flowers in the garden.

wild cherry in blossom

Wild cherry blossom.

gorse with Arthur's Seat in background

Gorse in flower, with Arthur's Seat in the background.

Posted in Gone for a walk

Blackford Hill gallivanting (3rd May 2007)

young sycamore leaves

Sycamore (Acer pseudoplatanus) - flower and new leaves.

young sycamore leaves - backlit

Young sycamore leaves backlit by the Sun.

early elder inflorescence

Early elder (a.k.a. elderberry) (Sambucus nigra) inflorescence.

young sycamore leaves

The young leaves of a small sycamore which was decapitated when a patch of gorse was cleared. The sycamore is a lot quicker off the mark in terms of recovery, by the look of things.

gorse shieldbug

The gorse shieldbug (Piezodorus lituratus). Tenuous tree link: feeds on gorse, which is almost a tree. A wannabe tree.

Posted in Gone for a walk

treeblog seedling update (Day 40)

It is Day 40. A whole forty days since Set A was planted. Almost 6 weeks. Seedlings have grown, but progress is disappointing. There are a fair few grey alder seedlings (I apologise for a lack of precise figures). Unfortunately, these do not appear to have made any progress in the week or so since the last update. Neither have the cider gum seedlings. In fact, the number of cider gum seedlings has apparently declined! This is a bit of a mystery; the seedlings are missing, and so presumably haven't just shrivelled up, and yet there is no sign of anything that may have eaten them. If they are being eaten, it must be a pest small enough to get through the wire mesh that protects them at night. And there is no sign of any slug or snail trails. And on the Scots pine front... well, there aren't any Scots pine seedlings (yet). Bah.

The photos below were taken on Saturday morning (Day 38).

The grey alder tray. Lots of seedlings - a pity they are so small.

A grey alder seedling.

Cider gum seedlings. Where are they vanishing to?

A cider gum seedling.

No sign of any Scots pine here...

...or is there?

Posted in The treeblog trees

The Capon Tree (May 2007)

Last Saturday I travelled back home from Edinburgh. The Capon Tree at Jedburgh is en route, so it was no trouble to stop and check it out again. The old veteran has made it though another winter and is now in full leaf. These photos just don't do justice to the Capon Tree's impressive size.

the Capon Tree

the 'front'

the 'back'

the lower bough

the upper bough

the Capon Tree

Posted in Notable trees

treeblog seedling update (Day 47)

Well, today is actually Day 49, but my photos are from Day 47 - Monday. So it is now seven weeks since Set A was planted. In the cider gum and grey alder trays, there are quite a few seedlings (roughly twenty in each), but these are still very small; somewhere in the order of a few millimetres to a centimetre or two. There is now a definite Scots pine seedling (and possibly a second), but this is also very small. Just about a centimetre. I predict that by this time next week, we should be seeing further Scots pine emergence and hopefully an increase in the size of the other seedlings. Compared with a sycamore seedling of similar age, the cider gums and surprises are tiny... but then again, sycamores do produce much larger seeds, and hence probably contain larger initial food reserves.

The last week has seen almost continual rainfall. An unusually high amount of rainfall. Yesterday's paper reported that some places in the UK had received half of May's expected rainfall in just 24 hours! We have also seen very heavy rain, which thankfully hasn't appeared to damage the treeblog seedlings. Nevertheless, the soil in the seed trays is pretty waterlogged. I hope that this won't cause the base of the seedlings to rot. That would be a shame.

A typical grey alder seedling.

A typical cider gum seedling.

The Scots pine alpha seedling.

Posted in The treeblog trees

The Plane Tree of Hippocrates

the Plane Tree of Hippocrates (June 26th 2006)

On the Greek island of Kos, an ancient plane tree occupies Platanou Square in the capital, Kos Town. Located close to the harbour and the Castle of the Knights, it is under this plane tree that Hippocrates, oft regarded as the 'Father of Medicine', is according to legend said to have taught many of his students some 2400 years ago. Another legend tells of St Paul the Apostle standing beneath the plane tree, speaking to the inhabitants of Kos and spreading the word of Christianity. According to Wikipedia its crown has a diameter of about 12 metres, which is currently supported by a cage of green-painted metal.

the Plane Tree of Hippocrates (June 26th 2006)

Contrary to the legends, the current tree is almost certainly not as old as they require. Yet it is likely that this tree is a descendant of the original tree, or perhaps a new tree that grew from the still-living roots of the original tree once its above-ground parts had expired. Thomas Pakenham, in his Remarkable Trees of the World (2002, Weidenfield & Nicolson), writes:

For centuries people have believed that this is the tree under which the great healer sat when he taught medicine to his disciples in the 5th century BC. I would like nothing more than to share their faith. [...] But kill-joys will point out that the wood of the oriental plane tree, Platanus orientalis, rots relatively quickly. Today the main trunk is a hollow shell like an old gourd. True, there are large branches growing out of the cage from the east side of the gourd; and there is a new trunk, layered from a branch on the west side about a century ago, now forming a delightful dome of young branches. But I doubt whether the original tree, whose trunk is now a shell, is older than 600 or 700 years.

But wait, say the fans of the great healer. Suppose there was a plane tree there in Hippocrates' day. Of course, it didn't live 2500 years. But its roots did. [...] The trunk, this old gourd, may be the fourth generation of the great healer's trees sprung from the roots.

the Plane Tree of Hippocrates (August 3rd 2004)

I have visited the Plane Tree of Hippocrates twice; in August 2004 and again in June 2006. I must confess to being disappointed upon first seeing it, after hearing rumours of this legendary, ancient tree. But after visiting it for a second time, I could imagine its true size, as if its hollow trunk was still solid and whole.

the Plane Tree of Hippocrates (August 3rd 2004)

Posted in Notable trees + Holidays and field trips

treeblog seedling update (Day 55)

Bad news: The cider gum and grey alder seedlings seem to be in arrested development. I think it might be worth trying a different sort of soil. Only two Scots pines have germinated.

Good news: One of the Scots pines is looking nice and strong. It is definitely the pick of the treeblog crop:

The most advanced treeblog seedling yet (photographed yesterday).

The Scots pine seed tray. The alpha seedling is circled.

Posted in The treeblog trees

Scots pine (Pinus sylvestris) flowers

I took the following photographs of the reproductive parts of the Scots pine yesterday near the little village of Bolsterstone. The accompanying information comes from Forestry Commission Booklet No. 15, Know Your Conifers, authored by Herbert L. Edlin, B.Sc. and published by HMSO in 1970.

Male flowers.

Male flowers... consist of clusters of golden anthers, set some way back from the tips of the twigs; they shed clouds of pollen in May, and then wither.

A click beetle (Athous haemorrhoidalis) close to a male flower. Adult click beetles feed on pollen, nectar and flower and leaf tissues, but they do not feed exclusively on Scots pine.

Female flower.

The female flowers appear at the same time [as the male flowers], at the very tip of a newly expanded shoot; they are tiny, crimson tinted globes. After fertilisation they grow into brown structures no larger than a pea; they need two years for full ripening.

Two-year-old unripe cone.

Mature cones... which are always "one whorl back" from the tip of the shoot, owing to its continued growth, are at first green with tightly-shut scales. [...] Their symmetrical, "pointed-cone" shape helps the tree's identification; each scale bears a knob, but no points. In spring they turn brown and the scales open, to release the winged seeds... As in all pines, the seed is lightly held in a curved "claw" at the base of the wing.

A ripe, woody Scots pine cone, open for seed dispersal.

Posted in Miscellany

Whitwell Moor perimeter wander

The enemy in our midst. Rhododendron ponticum on heather moorland. The moorland appears to be under succession by birch woodland, although Rhododendron might end up taking over instead.

Photos taken on the 23rd of May 2007.

R. ponticum inflorescence.

Looking across fields towards the village of Bolsterstone between the branches of a hawthorn (Crataegus monogyna).

Female beech (Fagus sylvatica) flowers - these will transform into beechnuts over the next few months.

The twisted and tortured-looking trunk of a stunted Scots pine (Pinus sylvestris).

A beech seedling with one pair of cotyledons and one pair of 'proper' leaves.

A nice bit of semi-natural mixed woodland. Lots of beech and Scots pine and plenty of oak off-camera. The low shrubs in the foreground are bilberry (Myrtillus vaccinium).

Posted in Gone for a walk

treeblog seedling update (Day 62)

Better news than the last treeblog seedling update! Even though only two have germinated so far, the Scots pines are powering along. Both seedlings are looking strong and healthy, and the beta seedling is doing a good job of catching up with the alpha.

The alpha seedling is on the left, the beta seedling is on the right (photographed yesterday (Day 62) - not to scale).

And after what seems like an eternity with no change in the germinated cider gum and grey alder seedlings, they now appear to be on the verge of a growth spurt. A few of both the cider gums and the alders are now developing their first pair of real leaves. The grey alders are also looking sturdier than they were last week.

Two typical cider gum seedlings.

Two typical grey alder seedlings. Are those red twiddly things on the left seedling new leaves?

Posted in The treeblog trees

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