The Whitebeam { A study of Trees}-11

Whitebeam Sorbus aria surrounded by oil seed rape

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Introduction

This is the 11th article in the series 'The Study of Trees' where the intention is to help those interested in identifying trees but are unfamiliar with the species. Most people start their identification progress by recognizing the form and colour of their leaves.This is fine during the summer months but of little use when the foliage has fallen and the branches are left naked and bare. Yet every tree has a characteristic{s} that will help to identify the species even in the depths of winter. Here we review the Whitebeam Sorbus aria and its allies, a flowering tree that produces fruits.

Whitebeam late summer.

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General information and background.

The Whitebeam belongs to the Order of plants known as the Rosales and is placed in the family Rosaceae. they have been allocated the genus name of Sorbus and the scientific name of aria. For a long time it was referred to as Pirus aria before it was renamed Sorbus aria,but still a bone of contention among botanists and dendrologists And to the layman even more confusing in respect of the scientific name. DNA evidence show that our forefathers has some justification for their placement in Sorbus.

The two groups however, have marked differences particularly the foliage. Another tree of the Surbus genus the Rowan** has pinnated {leafs divided into leaflets},while the whitebeam have leaves that are simple with toothed or in some cases lobed margins. Both groups have trees that produce flowers and fruit. {berries}

The pinnate leaved Rowan is thus left in the genus Sorbus and joined by the White beam which in some cases is till referred to as being in the genus Pirus/Aria,and it may be some time before all the books make the change. Sometimes the two groups hybridize in the wild but this is uncommon.

The Whitebeam is a broad-leaved deciduous tree native to southern England but widely planted in the north. It is also native to many European countries. It is very commonly planted in parks and gardens though it is relatively rare in the wild.

** see my hub The Rowan a charming name and a charming tree.

Whats in a name?

The Whitebeam meaning white tree,beam deriving from the German baum a tree, { Hornbeam** also takes its name from the same source. The specific name of aria seems to have derived from the time of Theophratus a pupil of Aristotle.

Of the many local names this tree bears in the British Isles-" Cumberland {Cumbria} hawthorn" would seem merely to be one of Gerard's {1500's} deliberate coinages. Sea-Ouler quoted by Parkinson, in that part of England is merely sea alder,the tree being especially luxuriant on the exposed seaward front of the mountain limestone hills of Lancashire,and the leaf being sufficiently similar to that of the alder***

Incidently there is a unique species of whitebeam that grows in my native county of Lancashire {NW England}, the Lancaster Whitebeam,it grows nowhere else in the world.

** see my hub History of trees Hornbeam

***see my hub The Elegant Alder Tree

You may also be interested in my hub the Lancaster Whitebeam.

Components of Sorbus aria

Jacob Sturm
Jacob Sturm | Source

Description of the Whitebeam, Sorbus aria

The bark.--- The old bark tends to be reddish brown and smooth,but the young shoots are covered with a white mealy down. The twigs later become smooth and have a shiny surface of a warm reddish or olive brown, marked with conspicuous round tenticels or cork-warts of a paler bluish colour

These long flexible shoots have given rise to such names as 'whip-crop' and 'whip-beam' the former shared with the Guelder roses** The tree also bears dwarf shoots of strikingly contrasting characters.These ' spurs' are also pubescent,but are rugged throughout their entire surface with prominent rings of leaf scars,the inter-nodes of the stem between them being practically undeveloped,so that the leaves are borne in tufts.

The spurs are given off from the stems at angles approximately 45 degrees and not infrequently several of them, each one or two inches long,spring in succession from earlier shoots of the same character. The conical egg-shaped ,olive green buds are directed upwards ,but are not flattened against the stem the one which terminates the shoot may well be larger than the lateral ones. The bud scales are green with brown margins,which are are slightly downy and exude a sticky secretion.

The down on the young twigs and on the margins and inner surface of some bud scales,are over-lapping protections. The viscid secretion with which they are bound together is an adaption for the exposed situations of the tree. However, the warm blanket like wrappings do not act in the manner as might be supposed. They are not mere 'blankets' to keep out the frost,for the delicate bud tissues may frequently be encountered during the winter with their moisture congealed to ice in spite of these wrappings,and without any permanent injury to the embryonic shoot.

It is probably the sudden freezing or thawing out which proves so fatally destructive to plant tissues,expanding the water they contain into ice crystals, so that the cells are ruptured and torn in the process. leathery scales,gummy excretions of hair, and thick felts of hair,would seem therefore,to be mainly effective at keeping out damp and moisture from the outside and by moderating any changes of temperature within the protected structure, in either a downward or upward direction.

** See my hub The Guelder rose.

trunk of Sorbus aria

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Close up of the foliage

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The leaves of Sorbus aria

No part of the tree,suggests this care for provision against the cold so much as the leaves themselves. When they are young they are 'plicate' or plaited in a somewhat fan-like manner,but as the secondary veins spring from the mid-rib in a pinnate manner this folding is not that of an ordinary fan but rather an elongated central axis.

In addition to this plication the two sides of the leaf are so folded towards one another that as they emerge from the bud, only the under surface is exposed and whatever the position of the shoot that bears them, they always assume an upright position. the position of the young leaf is explained as exposing a minimum of surface of the leaves to the cold radiating from the ground beneath them.

Both surfaces of the leaf is at first grey with a webbing of fine hairs, but these soon disappear from the upper surface,leaving them a shiny dark green, while the under surface becomes covered by the dense snow-white down which gives the tree its characteristic appearance as it sways in the breeze.

The leaf stalks are downy and soft, not much exceeding one fifth of an inch the length of the blade,and the stipules soon disappear. The blade of the leaf may vary considerably in size and form. the typical tree in the south of England has broadly elliptical leaves from three to five inches long with the margin coarsely and irregularly toothed,except at the wedge of the base.

there are from nine to fourteen prominent secondary veins from each side of the mid-rib running nearly straight to the periphery. These secondary veins are sometimes opposite to one another,sometimes not, and are connected by a network of very fine tertiary vein-lets.

paler under side of Leaf

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Whitebeam flowers and the simple undivided leaves.

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Sorbus flowers,fruits and foliage

courtesy of the BHL
courtesy of the BHL

The flowers.

The flowers of the whitebeam appear in May or June,its blossoms being in a loose flat clusters with downy stalks,each individual flower being half an inch across,larger individually than those of the Rowan flowers,although the clusters themselves are not as large.

As is typical of the Rosales they have five petals ad the styles vary in number from 2-4, but seem to be most commonly in threes and are thickly covered by hairs at the base. The flowers are in botanical parlance Hermaphrodite { each flower contains both male and female productive organs.} the flowers are pollinated by insects.

Fruits forming

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The fruits.

By October the fruits which succeed the flowers are ripe having turned from green to a bright scarlet colour dotted over with little brown points which give rise to the country name of Chess-apples.

They are sub-globose and about half an inch in diameter, their orange-coloured flesh is mealy and acidic and astringent until bletted {decayed or over ripe} The case is leathery and contains two seeds.

Squirrels,hedgehogs and birds gorge on these hedgerow 'apples'.

Ripe fruits of the Whitebeam

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Rock Whitebeam Upper Leaf

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Whitebeams in cultivation

Though several varieties have been described in cultivation,such as Sorbus obtusifolia {blunt},S.acutifolia {sharp}, S,undulata {wavy} S.angustifolia {narrow},and S.rotundifolia {round}which differ from the typical type merely in the minor characteristics of the leaves which their names indicate. of all the species which were recorded in the past, only six or seven of them presented features worthy of note.

Sorbus rupicola or Rock Whitebeam,described from exceptional exposed situations, may merely be a depauperate form. However, it has smaller fruit than the 'type' and its leaves, not only differ in form, being obovate,deeply lobed in their upper half and narrower and entire below, but have secondary veins reduced to from five to eight pairs. It is now regarded as a distinct species and is also found in Norway,Sweden and Russia.

Sorbus rupicola or Rock whitebeam in its natural habitat

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Leaf of Sorbus intermedia

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Other species

Sorbus rotundifolia forms a small tree 18-30 feet high {rarely 50'}, with broad oval or oblong or sub-orbicular lobed leaves with grey felt on the under sides. The flowers have a remarkably sickly and disagreeable smell. The globose fruits may exceed half an inch in diameter, and are at first olive brown with lighter dots, but by October or November become reddish but never as bright as the common whitebeam. Their flesh becomes an apricot colour.

Sorbus intermedia, is a native of Sweden and has frequently naturalized in the British isles. In its native surroundings it grows to an altitude of 4,500 feet in the Alps and at 6,000 feet in the Pyrenees. A small tree, its leaves are oblong,toothed and pinnatified near the base and white beneath. The fruit is scarlet with a pulpy yellow flesh

Sorbus intermedia Fruits and leaves

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Other forms

Professor Babbington designated another form S fennica with partly divided leaves which were grew webbed and producing sweet scented flowers which is almost certainly a hybrid between the whitebeam and the Rowan Sorbus acuparia.

The Rev Augustin Ley discovered a species in the Breconshire mountains growing at an altitude of 1,66 feet.Its leaves were divied, but narrower than those of S.intermedia,its flowers have the perfume of the hawthorn,and its small globular fruits ripen by the beginning of September to a bright coral red. It appears most closely allied to s.intermosa.

Sorbus aria autumn colours and fading fruits

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4 comments

D.A.L. profile image

D.A.L. 2 years ago from Lancashire north west England Author

aviannovice,

Hi Deb, Your welcome, glad to have introduced this species to you. Best wishes to you.


aviannovice profile image

aviannovice 2 years ago from Stillwater, OK

I didn't know about this beautiful tree! Thanks.


D.A.L. profile image

D.A.L. 2 years ago from Lancashire north west England Author

DDE,

Hello Devika, glad you enjoyed this one. You are so right about trees having a beauty in our landscapes I would not like to be in tree-less place. Thank you for your vote up ,you are appreciated. Best wishes to you .


DDE profile image

DDE 2 years ago from Dubrovnik, Croatia

Incredible photos. A wonderful sight of this kind of tree and of its importance. You always show me the best of your hubs. This is amazing of how much of beauty trees have to our environment. Voted up, interesting.

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