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Trees on the Common: Thorn

Trees on the Common: Thorn

This week on the Common: Spring is advancing in leaps and bounds – the chestnut trees are decorated with their candles, the hybrid apple trees are laden with blossom, buttercups have begun to flower in the meadow and I spent a happy couple of minutes watching an amazing ‘beefly’ with its long proboscis, carefully hovering to  gather nectar from a patch of forget-me-not. Our conservation assistant, Will Scott-Mends, reported hearing a Cettis warbler in the reedbed. This is a first for us: we can only hope that it is undisturbed and chooses to make a home here.  Quieter times and reduced pollution make this is a great time to look skyward at night, to enjoy the buzz of insects and to drink in the scents of blossom and ground fresh with rain.

Blackthorn in April 2020

Ne’er cast a clout ‘til  May be out – and it very nearly is….We are fortunate to have two naturally occurring native species of Thorn on the Common.

Hawthorn (Crateagus monogyna), also known as May, can grow to a tree of about 15m. It is the only tree specifically linked to a month of the year. Flowers typically appear around May Day in a profusion of white, after the appearance of small, maple-like leaves.

The leaves are deeply lobed and quite small at 4-6cm long. The bark is reddish brown and breaks into rectangular platelets, while the trunk (which may be single or multiple) often has a knotted, fissured and wizened look. Its highly dense, pale pink wood is useful for turnery (for handles, boxes, even boat parts), as well as having high fuel value for wood and charcoal.

Fruits appear in clusters of red berries (‘haws’) later in the year and will hang until Spring unless eaten by birds. Haws can upset our own stomachs if eaten raw but when cooked – often with the vitamin C-rich rose hips – and sieved to create a jelly, they are a source of vitamins and antioxidants. Seeds have such a tough outer shell that they need to be in the ground for two winters before the tiny root (radicle) can break through and start a new plant.

Around the Common, you can find hawthorns in hedges and as individual trees. The tree in the main photo has with five large trunks and with the largest having a 1.2m girth at 1.2m from the ground, is designated ‘significant’. From this we estimate its age at 160-240 years, making this magnificent tree a strong contender for one of the oldest on the Common.

Blackthorn (Prunus s

pinosa) or Sloe, tends to grow as more of a bush, rarely exceeding 5m. Left unma

naged, blackthorn spreads by suckering, creating large thickets that can be seen in at least four parts of the Common (this means that rooted whips can be sourced and transplanted very easily in winter).

Large drifts of Blackthorn’s white flowers are among the first to herald the coming of Spring and appear several weeks before Hawthorn flowers as in this photo taken March 2020. Blackthorn differs from Hawthorn in that its flowers appear long before its leaves, that are small, elongated, oval and toothed. With sharp thorns along each twig that itself ends in a pointed thorn, blackthorn can be a vicious plant, as any gardener or woodsman caught by its thorns will confirm. The bark is dark brown, smooth and in winter the twigs look black and spiny.  The wood is tough and yellow, traditionally used for walking sticks and in Ireland, for shillelaghs.

The familiar fruits (sloes) are dark blue/black. Sloes are thought to be the crop-wild ancestors of our domesticated gages, damsons and plums.  They are extremely sour, full of tannins (another antioxidant) and used to infuse gin – wonderful for warming a cold winter work party (a much-appreciated FoBC tradition instigated by member Dennis Brown).

Hedging:  Both species have traditionally been used in hedging because as mentioned, they form a thorny and impenetrable barrier that is very useful for stock control (a possible an inspiration for barbed wire).  The ease of propagation and speed of growth for hedging led to the common name ‘Quickset’ and is applied to either species, but especially hawthorn.

A managed hedge will thicken when trimmed. Gaps at lower levels can be filled by hedge-laying (the craft of partially cutting and bending over the trunk, weaving it between stakes, typically of hazel – often planted along with blackthorn in a hedge.  So long as the stems have not been wholly cut through, the plant will re-shoot with new verticals, giving fresh life to the hedge as an effective barrier.

Putney Boundary: Competition between land, people and animals is not a new thing. In 1594, as the population began to recover from the effects of the Black Death, there was massive rivalry over grazing between residents of Putney and Barnes, when ‘heads were broken’ (someone was killed). This event led Queen Elizabeth I to order a boundary ditch be dug and a hedge planted to stop cattle (a term referring to any domestic animal owned as a chattel: cows, pigs and sheep) from crossing the boundary.  Is the thicket of blackthorn near the boundary today a remnant of that original hedge?   I certainly like to think so!

Biodiversity: Blackthorn is the food plant for numerous moths and other invertebrates, as well as where the rare brown and black hairstreak butterflies lay their eggs. We have also seen eggs of the blue-bordered carpet moth on our blackthorn, which can be confused with the eggs of the brown hairstreak. Its early flowering provides a vital nectar source for pollinators. Hawthorn hosts more than 300 insects and its profusion of berries supports many migrating as well as local birds.

Mythology and beliefs: Hawthorn are deeply rooted in our pastoral/pagan past (the term ‘pagan’, only recorded in English from around 1375, derives from Latin ‘paganus’ meaning rural or rustic and originally had no religious connotation). Hawthorn is a symbol of Spring, Fertility, and provided the wreath or garland of the Green Man.  In one tale,  its petals formed the Milky Way.  Pre-Christian Celtic culture revered the hawthorn and in Ireland it is associated with the Faery Queen and the Little People:  in 1999, a single tree brought the building of a motorway to a halt in Co Clare, necessitating a deviation. In England it is more associated with love and the arrival of Summer, with special mention for the Glastonbury thorn.

Thorns also have a dark side in mythology:  Blackthorn has long been associated with witchcraft: providing wands and staffs for witches, some trees appearing gnarled and hag-ridden, some with gall induced ‘witch’s broom’. There is also a superstition that you must not bring hawthorn into the home, as it will bring disease if not death with it as it was said to ‘smell of the Plague’. Interestingly, science has established that hawthorn blossom contains trimethylamine, a chemical which is one of the early releases when animal tissue decays – so there was good reason for the relationship, even if that is unfair on the hawthorn (a possible adaptation to attract pollinators).

Ne’er drop a clout ‘til May be outis today often thought to mean beware of frosts until the month of May has passed. More likely it is linked to the flowering time of the hawthorn, as a country sign that the risk of frost has passed and Summer arrived. It is interesting to note how things can become lost or change over time: some speculate that this would have been more salient before the adoption of the Gregorian calendar in 1752, when May 1 was shifted a fortnight earlier. In our time, climate change may play a part: from the look of the buds on the Common, this year May will be out several weeks earlier than ‘normal’.

Other thorns on the Common:

Midland Thorn (Crateagus laevigata) is a native, but due to its pretty pink flowers has also been bred as a garden ornamental tree. Any thorn seen on the Common with pink or red flowers is almost certainly a hybrid garden escape.  It is otherwise very similar to hawthorn, although its haws have double seeds and are a little bigger and brighter.

Purging Buckthorn (Rhamnus catharticus) has been introduced in recent hedge plantings as it is a good host plant for butterflies, especially brimstones, and other insects. Flowers, leaves and berries cluster on short stems with thorns (shaped like a buck’s antlers) whilst longer stems provide growth. The shiny black berries are poisonous to humans, having a purgative (laxative) effect in small doses.

Next week:  Willows

MH 20.4.20

Holland M FLS and Giordano P; 2020; I Ate Sunshine for Breakfast; Flying Eye Books: London


The Irish Times. Fairy Bush Survives Motorway Planners. Saturday 29th May 1999

Glastonbury Abbey; The Holy Thorn