As the days shorten and the light levels fall the woods settle down for winter dormancy, but this season is worthy of a woodland walk for the rainbow of colours and the hidden activity that takes place to put on this glorious display. The green of the summer is disappearing into the yellows, reds and browns of autumn as a prelude to the trees finally shedding their leaves and the berries remain for the duration – until they are picked off by the woodland wildlife. Two walking routes, described in the new Woods and Trees Trail, give lots of opportunities to see a bumper crop of berries and to revel in the woods and trees at this time of year.
In summer, the predominate colour in the woodlands is green as the chlorophyll in the leaves absorbs all the colours of sunlight, except green, and we see this reflected light. As the days become shorter and temperatures cool, less and less chlorophyll is produced and once the rate of production falls below the rate of decomposition, the pigment’s presence in leaves — and its characteristic green colour — begins to dwindle.
At this point some leaves, such as those of birches, begin to appear yellow or orange because we now see the carotenoid pigments (such as carotene that gives carrots their orange colour). These are present all year, but hidden from our vision by the chlorophyll. Carotenoids aid photosynthesis by absorbing blue and blue-green wavelengths, so the light that they reflect appears yellow to us.
But the red in leaves and berries are special – they contain anthocyanins which absorb blue, blue-green, and green light so we see them as a scarlet or purple colour. Foliage that turns red in autumn expends energy, producing anthocyanins at a time when energy is less available with the shortened days. It is not fully understood why they do this, but there must be some advantage. It has been found that these trees can continue to absorb nutrients for longer, optimising the last rays of sunshine, they may act as a sunscreen to protect the leaves from damage as the chlorophyll levels drop, or they may enhance the plants defences against insect damage – no one is entirely sure.
Both permanent and transient conditions will influence colour – anthocyanin production is especially prolific in cold, sunny conditions but individual leaves will vary depending upon the ratio of carotenoids to anthocyanins. The reduction of light levels, is the most significant factor triggering the shutdown of chlorophyll production and triggering anthocyanin synthesis, alongside existing carotenoid levels, that gives rise to the beautiful range of colours we are currently seeing on the reserve.
High levels of anthocyanins is also the component that makes berries the rich red, or purple. Historically this was thought to be sign of bad weather to come, but we now know it is due to spring conditions – though flowering and fruiting can be idiosyncratic. Berries are rich in nutrients and vitamins – the dry pith of ivy berries contains nearly as many calories as Mars bars and whilst red berries are often thought to be consumed by birds and other wildlife, preferentially to other colours, the answer may be simply the colour contrast. Many trees that produce red berries do so whilst the leaves are still green, or are evergreen so they are easy to spot.
The scarlet berries of holly Ilex aquifolium are common along the track boundaries on the reserve and the berries that can be seen on mature trees are a vital source of food for birds and small mammals, such as our resident dormice during the autumn and winter. Holly is dioecious, meaning that male and female flowers occur on different trees so to produce berries there must be both male and female trees present in the woodland.
The proliferation of holly shrubs and trees on the reserve is mainly the result of bird sown seedlings rooting under roosts, a likely culprit is jays, or from suckering under the leaf litter. Holly leaves also provide fodder as it has one of the highest calorific content of leaves browsed by animals. In ancient times holly was pollarded to provide winter stock feed – our resident Dartmoor pony herd browse on young shoots – look out for the spineless leaves that often occur where browsing occurs and sometimes on whole specimens – called free or sloke holly.
Where grazing ceases holly can create a closed canopy and has been seen to grow around oak pollards and root in the forks of old oaks in Suffolk. Along the Old Manaton Road there are areas where the holly is being removed as part of the Building Resilience in South West Woodlands project, to open up light for the lichen assemblage and lower plants. Pagan tradition said lopping holly branches was allowed (if you asked permission first!) but there was a widespread belief that cutting down a whole tree brought bad luck. There is are common threads relating to pagan myths that runs through many of the tree species and fruiting berries that can be seen on the Woods and Trees Trail.
The Celtic name for the rowan Sorbus aucuparia, a common understorey tree in Yarner Wood, is ‘fid na ndruad’ which means wizards’ tree and was historically planted outside homes and in churchyards to ward off spirits. The berries are a rich source of autumn food for birds including thrushes and waxwings that prefer the rowan’s smaller seeds as they are only interested in the flesh, the seeds are not ingested and ultimately dispersed by the birds. Unlike the holly, the rowan is hermaphrodite, having both female and male parts on the same tree so produces berries on a single specimen after fertilisation by insects.
Berries are an important source of winter food for woodland birds with some species like thrushes, blackbirds, redwings and fieldfares finding most of their winter food from berries. The size of both the berry and seeds can be relevant to which bird species feeds on a particular berry types.
Larger berries like dog-rose hips from the wild rose family generally prove too large for birds smaller than blackbirds. Rosehips, sometimes called ‘heps’ or ‘Itchy-coos’, have a higher proportion of Vitamin C than any other common fruit or vegetable – a cup of rosehip pulp contains more than 40 oranges. With the lack of fresh fruit imports during the Second World War a voluntary collection scheme to process hose-hips into syrup was set up. County Herb Committees (who knew these existed!) harvested and processed 450 tons by the end of the war with collectors paid 3d a pound. National Rose Hip Syrup was sold or could be made using a Hedgerow Harvest booklet recipe from the Ministry of Food. Anyone attempting to do this needed to carefully remove all the prickly seeds as the hairs and lining of the seed are a dangerous internal irritant.
Birds that can make use of the seeds themselves are attracted to berries with large seeds, such as Hawthorn Crataegus monogyna. The haws are rich in antioxidants and said to taste of whey cheese (or for the 21st century shopper – avocado) and are eaten by migrating birds, such as redwings, fieldfares and thrushes. They provide a good overwintering food source for hazel dormice and other woodland mammals. The tree supports more than 300 insects and is the foodplant for many moth caterpillars.
It is also known as the May tree, the only UK plant named after the month in which flowers – although the flowers are often not out till late May as the change to our current Gregorian calendar in 1782 meant 11 days were ‘lost’ and the old May Day now occurs on 12 May. This may account for some of the discrepancy, although hawthorn has notoriously erratic flowering and is influenced by late winter/spring temperatures, as well as altitude and soil. Hawthorn has more positive pagan associations than noted for previous species – it is a symbol of fertility and has ancient associations with May Day celebrations however superstitions about not bringing into the house are now thought to be due to the triethylamine contained in hawthorn scent which is the first chemical produced when living tissue starts to decay – a gangrenous smell.
The dark fruit of the common Ivy Hedera helix form and ripen over winter providing much needed fruit for birds and mammals in early spring. The flowers heads are abundant at the moment providing an essential late source of nectar. Note the different shaped leaves on the fruiting stems.
Another black berry producing tree on the reserve is the Alder buckthorn Frangula alnus which had a reputation for causing a bang. It was cultivated historically in wartime as its timber made charcoal used in the production of high-quality gunpowder. On a more peaceful note, it is the foodplant of the brimstone butterfly and the small berries ripen from green to red in late summer and eventually to a dark purple or black in autumn.
An unusual but not to be missed footnote is the Spindle Euonymus europaeus tree on the trail. It’s shocking pink berries can be seen in the hedgerow as you exit onto the public highway by Drakeford Bridge, well worth a few steps off the trail to look at. Spindle is an ancient-woodland indicator that can live for more than 100 years with bright pink pumpkin shaped fruit containing bright orange seeds. Both the leaves and fruit are toxic to humans – the berries/seeds having a strong laxative effect. Despite this historically the fruit was baked and powdered for use as a headlice treatment. Whilst not recommended for humans, on a more positive note wildlife loves its leaves and fruit, and aphids flock to it, bringing with them an array of predators. Spindle’s hard yellow wood was used for making weighted sticks for hand spinning wool as the wood is heavy and smooth enough to rotate between fingers like a dowel, hence its common name.
So enjoy the array of autumnal colours in the woodland, whilst it is available, until it disappears for another year…
You can download a copy of the Woods and Trees Trail or you can pick up a paper copy at the Reservoir Bird Hide in Yarner Wood.
Written by Linda Corkerton
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