Early autumn leaves

click photo to enlarge
Autumn is upon us with the leaves of many species of tree starting to change colour. Leaf fall has begun too and our first collection from lawns and gravel can't be too distant. In my garden the flowering cherries are among the earliest to reflect the change that autumn brings, though the maples and silver birches aren't too far behind. The other day I was reflecting that even though, in recent years, the onset of autumn hasn't been marked with quite the dip in temperatures that I remember from, say, twenty or thirty years ago, nonetheless the change in the colour of trees is happening distinctly earlier. Moreover, this is down to a single species - the horse chestnut.

In a post of October 2010 I commented on the impact of the horse chestnut leaf miner moth (Cameraria ohridella) on trees in south-east England and parts of central England: how the burrowing larvae cause leaves to turn brown, become dry and crisp, then fall earlier than they would were the trees not infected. This activity begins in summer, but the way it appears to accelerate the onset of autumnal colour becomes very obvious in late August and September. My photograph of the River Welland and Deeping Gate bridge that I posted a couple of weeks ago features a horse chestnut on the left of the frame exhibiting quite deep browns and oranges due to the activity of this insect pest.  I don't have any data on which to base my opinion, but I have the distinct impression that I'm seeing increasing numbers of horse chestnuts that are affected. Certainly if the trend shown in these maps has continued during the past three years then the damage will be quite widespread across much of England and have made significant inroads in the west and north.

Today's landscape photograph doesn't show a horse chestnut but it does show a carpet of leaves from one that has been affected by the leaf miner (the tree is just out of shot). I took it when I recently spent a few days in the area where Cambridgeshire abuts Bedfordshire and Northamptonshire - in what was once the county of Huntingdonshire. More photographs from that trip coming next.

photograph and text © Tony Boughen

Camera: Sony RX100
Mode: Aperture Priority
Focal Length: 13.1mm (35mm - 35mm equiv.)
F No: f5.6
Shutter Speed: 1/40
ISO: 200
Exposure Compensation:  0 EV
Image Stabilisation: On

Hard times for horse chestnuts

click photo to enlarge

The horse chestnut (Aesculus hippocastanum) is thought to have been introduced into England in the sixteenth century, probably from its native haunts of south-east Europe. In our country it has rarely been put to any practical use. Early planters were often rich landowners, and they valued its appearance and its seeds which are a source of food for deer. The wood of the tree is soft, white and easily cleft, with no strong heartwood. Consequently it has few uses apart from firewood or cheap boxes, and its great popularity stems from its value in ornamental planting. Its majestic shape and size, the big, "fingered" leaves, the "candle" flowers of spring, and the prickly seeds with their mahogany coloured seeds (conkers) are the reason for it being so widely seen across our islands. It is found in parkland and on playing fields, along streets, on village greens, in copses and clumps, and intermingled in woodland, a delight for children and adults alike.

The photograph above shows an avenue of horse chestnuts at Kirby Hall, Northamptonshire. It was planted by the county's Girl Guide Association in 1935 to commemorate the Silver Jubilee of George V. A typical autumn photograph you might think, the conkers littering the drive, the leaves turning brown and orange. But all is not quite as idyllic as it looks. Those conkers are small, have fallen early, and the leaves shouldn't be quite so shrivelled and brown on the first couple of days of October. In years gone by they would be a multicoloured display of green, yellow, orange, red and brown. The reason for their premature fall and crisp, dark appearance is the horse chestnut leaf miner moth (Cameraria ohridella). The scourge of this species advanced rapidly across Europe, and was first detected in Britain in Wimbledon, London in July 2002. Since then it has spread throughout much of southern and central England as is advancing northwards and westwards at a rate of 40-60km a year. Unlike bleeding canker, the other principal disease of the horse chestnut, a leaf miner moth infestation is not terminal, merely an aesthetic problem. Nonetheless, research is being undertaken to try and control the disease.

My photograph was taken with the camera somewhere below the level of my knees. I felt the need to get away from shots taken from eye level.

photograph and text (c) T. Boughen

Camera: Lumix LX3
Mode: Aperture Priority
Focal Length: 5.1mm (24mm/35mm equiv.)
F No: f2
Shutter Speed: 1/30
ISO: 100
Exposure Compensation: 0 EV
Image Stabilisation: On