project reflections #20


In order to escape the violent winds that blew in these parts throughout early January, I took to rambling through the scattered woodlands along the banks of the river Don. Here I found many large sycamore maples or Acer pseudoplatanus  – a magnificent tree that will sometimes grow to a height of over a hundred feet.

I have observed that, in wet ground at the base of these sycamores, the rocking movement of the tree in high winds – transmitted from the upper branches down through the solid trunk – results in oscillatory movements within pools formed from groundwater. This fluid moves up and down with the back and forth movement, resulting in the water rising up and withdrawing – almost like breath – and often expelling the liquified soil to create cavities amongst the roots. These cavities are, I am led to understand, known as oscillants …

Acer pseudoplatanus, the sycamore maple, is a species of maple native to central Europe and southwestern Asia, from France it is naturally distributed eastwards towards the Ukraine, and south to northern Spain, northern Turkey, and the Caucasus. It is not related to other trees called sycamore or plane tree in the Platanus genus. Its apparent similarity to the species of that genus led to its being named pseudoplatanus, using the prefix pseudo- (from the Ancient Greek for “false”). Other common names for the tree include false plane-tree, great maple, Scottish maple, mock-plane, sycamore or Celtic maple.

It is a large deciduous tree that reaches 20–35 m tall at maturity, with a broad, domed crown. On young trees, the bark is smooth and grey but becomes rougher with age and breaks up in scales, exposing the pale-brown-to-pinkish inner bark. The leaves are opposite, large, 10–25 cm long and broad with a 5–15 cm petiole, with a leathery texture, palmately veined with thick veins protruding on the underside surface, with five lobes with toothed edges, and dark green in colour with a whitish underside. The leaves are often marked with black spots or patches which are caused by the fungus Rhytisma acerinum. The monoecious yellow-green flowers are produced in spring on 10–20 cm pendulous racemes, with 20–50 flowers on each stalk. The 5–10 mm diameter seeds are paired in samaras, each seed with a 20–40 mm long wing to catch the wind and rotate when they fall; this helps them to spread further from the parent tree. The seeds are mature in autumn about 6 months after pollination.

The name “sycamore” originally belongs to the fig species Ficus sycomorus, which is native to southwest Asia (this is the sycamore or sycomore referred to in the Bible). The name was later applied to this species by reason of the superficial similarity in leaf shape.

The sycamore is cultivated and widely naturalised north of its native range in northern Europe, and it now occurs throughout the British Isles, having been introduced in the 17th century. It is considered to be an environmental weed in environmentally sensitive locations.

The wood is a medium weight hardwood, weighing 630 kg per cubic metre. It is traditionally used in making the backs, necks and scrolls of violins. The flowers produce abundant nectar, which makes a fragrant, delicately flavoured and pale-coloured honey.

Paul Evans, 8 January 2012

project reflections #19

Briar and Bracken

On the clearest day in December I visited the long-abandoned burial grounds of Wardsend. These range across a hillside that faces roughly south west, somewhat towards the setting winter sun as it falls below the occupations on the valley ridge of Upperthorpe. About the many forgotten memorials, each delicately graven with the names of the dead, I observed an abundance of the growth-fronds of common bracken Pteridium aquilinum – now brown, friable and themselves long dead after the summer blaze of green – and also many dormant briars or brambles of the blackberry Rubus fruticosus

 Part I: Briar or Bramble?

Briar or brier is a common name for a number of unrelated thicket-forming thorny plants, including species in the Rubus genera. Rubus is a large genus of flowering plants in the rose family, Rosaceae. Blackberries  are a common, widely distributed member of the genus. Blackberries, as well as various other Rubus species with mounding or rambling growth habits, are often called brambles. The genus Rubus is believed to have existed since at least 23.7 to 36.6 million years ago.

Most of the Rubus briars have woody stems with prickles like roses; spines, bristles, and gland-tipped hairs are also common in the genus. The Rubus fruit is an aggregate of small units known as drupelets. In blackberries the flower receptacle is elongate and part of the ripe fruit, making the blackberry an aggregate-accessory fruit.

The generic name means blackberry in Latin and is derived from the word ruber, meaning “red”.

The  word bramble comes from Germanic bram-bezi, whence also German Brombeere , Dutch Braam and French framboise. In popular UK usage the term primarily refers to the blackberry bush; in Scotland and the north of England it refers to both the blackberry bush and its fruits.

The scientific study of brambles is known as batology.

Bramble bushes have a distinctive growth form. They send up long, arching canes that do not flower or set fruit until the second year of growth. Many types of brambles bear edible fruit, and many have recurved thorns that dig into clothing and flesh when the victim tries to pull away from them. Some types also have hair-like thorns. Brambles usually have trifoliate or palmately-compound leaves.

One cup of blackberries contains approximately 0.029 mg of thiamine (vitamin B1).

Part II: Bracken

Pteridium aquilinum (Bracken or Common Bracken) is one of several species of large, coarse ferns of the genus Pteridium.

Ferns (Pteridophyta) are vascular plants that have alternating generations: large plants that produce spores and small plants that produce sex cells (eggs and sperm). Brackens are in the family Dennstaedtiaceae, which are noted for their large, highly divided leaves. Brackens are cosmopolitan, being found on all continents except Antarctica and in all environments except deserts. The genus probably has the widest distribution of any fern genus in the world. In the past, the genus was commonly treated as having only one species, Pteridium aquilinum, but the recent trend is to subdivide it into about ten species.

The word bracken is of Old Norse origin, related to the Swedish word bräken, meaning fern.

Evolutionarily, bracken may be considered to be one of the most successful ferns. It is also one of the oldest, with fossil records stretching back over 55 million years. The plant sends up large, triangular fronds from a wide-creeping underground rootstock, and may form dense thickets. This rootstock may travel a metre or more underground between fronds. The fronds may grow up to 2.5 m (8 ft) long – or longer with support, but typically are in the range of 0.6–2 m (2–6 feet) high. In cold environments bracken is winter-deciduous, requires well-drained soil, and is generally found growing on the sides of hills. The spores used in reproduction are produced on the underside edges of the leaf in structures called sori. The linear pattern of these sori is different from other ferns which are circular and located towards the centre. Dead bracken provides a warm microclimate for development of the immature stages.

Pteridium aquilinum is the most common species. It has caused such a problem of invading pastureland that at one time the British government instigated an eradication programme. Special filters have been used on some British water supplies to filter out the bracken spores.

Bracken fronds contain a variety of poisons: ptaquiloside or PTQ, pterosins and some metabolites. The plant is carcinogenic to animals such as mice, rats, horses and cattle when ingested, although they will usually avoid eating it unless nothing else is available. The spores have also been implicated as a carcinogen; Danish scientist Lars Holm Rasmussen released a study in 2004 showing that the carcinogenic compound in bracken, ptaquiloside or PTQ, can leach from the plant into the water supply, which may explain an increase in the incidence of gastric and oesophageal cancers in bracken-rich areas.

Uncooked bracken also contains the enzyme thiaminase which destroys thiamine (vitamin B1).

Paul Evans, 5 January 2012