IN RECENT days, I came across an old saying that summer begins when the flowers of the elder tree burst into bloom, and it ends when they ripen into elderberries.

On my morning walk today (slightly more than a fortnight before these notes appear in print), I noticed that the flowers of the elders along my daily route had suddenly blossomed, almost as if they had been awaiting the official start of summer before showing their wild beauty.

As a herald of summer, their timing was perfect and this ancient belief corresponds with another which goes: you may shear your sheep when the elder blossoms peep.

And as I settle down to these notes with the elder in flower all around me, the weather is fiercely hot and sunny, a real touch of summer. A hillside field opposite my study window is full of elders which are dripping with those large clusters of tiny white flowers, and the sun is beating down and scorching the earth.

In thinking of the elder so far as our weather is concerned, however, the countryfolk of the Middle Ages believed that witches could produce bad weather by stirring water with the branches of the elder tree.

I am not sure how that odd belief arose, but witches have long been associated with this most common of countryside trees.

Another very common but interesting bloom which reminds us of its presence at this time of year is the rosebay mallow herb, a tall, straggly weed which tends to grow in huge clumps on waste ground. Although it is a persistent weed, it is quite a handsome, elegant and colourful flower with a tower of rose-pink blooms and in fact it used to be cultivated by Victorian gardeners because of its attractive appearance.

It was prized as an ornamental plant and it was far from common, especially in the wild. Its rapid colonisation of rough areas seems to have occurred with surprising speed and efficiency in the period following the Second World War, so much so that it is regarded as a problem in some places.

This might be due to the fact that it thrives on land which has been disturbed and laid to waste, especially if the ground in question has been cleared by fire. For this reason, it is sometimes called the fireweed, and there is little doubt it loves derelict city-centre or industrial sites. Even now, that is where it is most regularly seen - disused railway sidings, tumbledown industrial premises and old factory sites are its breeding grounds.

There is no doubt the spread of the fireweed increased following the Second World War; it appeared on many sites which had been bombed or razed to the ground, but it loves the countryside too, often appearing on woodland sites which have been cleared of trees.

The problem is that it smothers everything else beneath it. It grows in such large, tightly-packed clusters that little else can survive. It is most effective at preventing the growth of other plants, whether wild or cultivated, and it does so by the sheer density of its presence.

Part of its ability to reproduce with such efficiency is due to the fact it has two methods of regeneration. In the autumn, it produces a long thin pod and when this is ripe, it splits along its length and the two parts curl back to scattered masses of seeds. Each seed is equipped with a tuft of down which enables it to float on the slightest breath of wind and many of us will recall the downy white clouds which rise from beds of rosebay willowherbs in the autumn.

The seeds float away in huge numbers and travel long distances on the wind, later to settle in places where the new plant can be rapidly established. In addition to this very efficient seeding system, however, the plant's roots also throw up new shoots at intervals. The established roots of a mature plant are very strong and woody, and they tend to extend horizontally rather than vertically, thus enabling the weed to spread quickly over a large area.

This dual means of reproduction ensures that its survival rate is highly effective and although it can be a troublesome weed, its lovely pink blossom does attract masses of bees - it is said that bee-keepers know when their bees have been to a willowherb site because they return covered in dusty white pollen, and the resultant honey is highly prized.

Ambush update

Following my notes about sparrowhawks ambushing their prey near places of human habitation (D&S June 16), I have received a letter from a lady in Ripon who writes of several similar experiences. She lives in a mews house in the town, very close to Ripon cathedral. She tells how last year, a sparrowhawk caught a greenfinch and plucked it on her garden fence, then this year the hawk dived on to an unsuspecting blackbird, having followed it onto a neighbouring lawn. My correspondent did her best to drive away the sparrowhawk and it did leave - but it took the blackbird with it. Only a week later, it chased another blackbird on to her patio but she managed to scare away the hawk leaving a very shaken blackbird crouching there. It flew off a few minutes later, leaving behind a pile of feathers. It had survived the attack, albeit possibly with some injuries. However, some good appears to have resulted from the sparrowhawk's liking for this town area. My correspondent tells how her conservatory roof was adopted by a lost racing pigeon which settled there for a long time. Unfortunately, it made a dreadful mess during its stay and steadfastly refused to leave.

She had to go away for ten days though, and when she returned the pigeon had left - thanks, she thinks, to the activities of the neighbourhood sparrowhawk.

Remarkable heritage

I was surprised to learn that, little more than a century ago, there were plans to construct a railway bridge across Aysgarth Falls. The proposal was that the bridge should be built of brick and its purpose was to link the line from Skipton with the Wensleydale line.

One might expect that, at a time of vast industrial growth when many similar developments were commonplace, such a proposal would have found ready acceptance but it did not. There was a massive outcry, not only in Wensleydale but throughout the country.

An association was formed to protect the falls from this kind of official vandalism and it attracted some of the best known and most influential people of the time. The president was Lord Wharnecliffe and he succeeded in taking his appeal to the House of Lords with the eventual result that the project was abandoned.

Some bridges were built in spectacular settings, however, and today we regard them as assets - for example, there is the remarkable viaduct which forms part of the Settle-Carlisle railway. This is the famous Ribblehead viaduct with its 24 arches spanning more than 400 yards and rising to 100 feet in height.

It took 6,000 men seven years to build the 73-mile long railway; the bridge alone required the work of 1,500 men and they all lived in shanty-towns in the area. Ribblehead viaduct was opened in 1876, and although I am not familiar with the protests which might have been generated at the time, if anyone proposed to demolish it now, there would be a huge outcry.

Happily, the viaduct is now part of a wonderfully spectacular route which is enjoying a revival in both passenger and freight traffic. Another spectacular brick viaduct spans the River Esk between Ruswarp and Whitby. This was opened in 1884; it required seven million bricks, enough to build 500 six-room houses, and the viaduct is 120 ft high with 13 arches.

With the closure of the Scarborough-Whitby line in 1965, the viaduct fell into disuse and although it has not borne a railway train for many years, it continues to dominate the scenery as people wonder what on earth to do with it. What can be done with such a massive structure, handsome though it is? I think there would be a huge fuss if someone suggested its demolition.