For generations, the people of South Tawton village have gathered for funeral wakes and christenings in their early 16th-century village hall and commented on the blackened thatch on the inside of its roof. Perhaps by chance, every time the outer thatch on the roof has been replaced over the years, this ebony-coloured underthatch had been left undisturbed.
What no one in this picturesque south Devon village realised was that this pitch-black underthatch - kept dry by the waterproof thatch on top and preserved by soot from former open fires below - consisted of a cornucopia of plants grown hereabouts and included in the thatch when their hall, known as Church House, was built. In fact it is an amazing historic record of land use and farming in the middle ages.
"We are planning to restore Church House," says David Youle, treasurer of its management committee, "so we asked Deborah Griffiths, head of archaeology and historic buildings at Dartmoor national park, to give us some advice. She noticed the blackened underthatch straight away and realised its significance. Luckily, no one had boarded it over on the inside years ago or we would have forgotten that it was there."
Church House is not unique. Not quite. But it is one of only 250 or so medieval buildings left in Britain whose underthatch has never been replaced. Compared with fragments of charred or waterlogged plant material and seeds preserved in burials, or scant references in parchment manuscripts to crop growing, these armfuls of plants cut and carried by medieval thatchers five centuries back - of wheats, rye and other cereals, wild flowers, ferns and vegetables - are a veritable treasure trove of information.
John Letts, an archaeobotanist at Reading University, has documented the underthatch contents of 50 or more of these special buildings and is looking at samples from Church House.
"Archaeologists used to assume that, although some thatched buildings date from the middle ages, their thatch was modern because it was replaced every few decades," says Letts.
"But some thatchers left the original underthatch in place rather than disturb it. They replaced only the thick outerthatch that waterproofs the building. So, on some buildings, the plants comprising the underthatch are perfectly preserved, albeit smoke-blackened. Soot from open fires in the past and dry conditions have limited insect and fungal degradation."
Most of Letts' samples of this ancient cultivated flora comprise bread wheat straw, rivet wheat - now never grown but which may then have been used for beer-making, rye varieties that grew as tall as six feet, and oats.
"What's striking," says Letts, "is the huge variety of cereals which must have produced different grain yields, straw [stem] lengths and ripening times, virtually guaranteeing that at least part of the crop would flourish in any one year irrespective of the weather. This enormous crop diversity has been lost as farming has become increasingly dominated by plant breeders and monocultures." Letts has identified 35 or more plants mixed in with this ancient thatch other than cereal straws. Today's cereal farmers equally despise some, such as charlock, mayweed, docks and thistles. Easily annihilated now with selective herbicides, medieval farmers would have had to pull them out or hoe them by hand. Sky-blue cornflowers and mauve corncockles, flowers on the brink of extinction these days, must then have been common among the wheat.
Letts has found pieces of pea and broad bean plants, leftovers perhaps from a previous crop rotation as well as bracken, that toughie fern now never seen in intensively managed farmland. It may have been grown commonly in field margins and damp furrows and harvested for animal bedding and fuel. Some of it got into the thatch, presumably by accident.
So the strip fields of medieval lowland England would have varied considerably in cereal colour, texture and crop height. They would have been speckled with a variety of flowers. Strips of leguminous vegetables, patches of bracken and wooden hurdle-bounded pasture for livestock grazing would have added more variety.
From the types and sizes of wheat straw preserved in the thatch, Letts believes that, contrary to previous opinion, medieval farmers didn't fertilise their fields much, if at all.
"The soil was often poor. But many of their cereal varieties were incredibly tall. If they had fertilised the soil, I think these cereals would have grown so large they would have fallen over. They were letting fields lie fallow for a year not to recover their fertility but so that they could hoe and plough the soil using oxen to keep weeds at bay. Weeds must have been a real problem," says Letts.
According to Chris Wood, senior architectural conservator at English Heritage, there are perhaps 50,000 thatched buildings in England, 24,000 of them listed for their historic significance. Most are in southern England, and Devon has a particularly high proportion. The vast majority have no original underthatch left.
"The problem is that most re-thatching, especially in recent years, has involved removing all of the old thatch," says Wood. "Local authorities have seen thatching as artisan rural employment and have rarely made it subject to the development control that other aspects of building modification are subject to. "We have been advising them to insist on old underthatch being retained and John Letts called in if they think the underthatch is ancient. He's the foremost authority and is respected as a good historian."
In recent years, the problem has been exacerbated by the modern fad to replace straw thatch with supposedly superior water reed. When this happens, all of the old straw thatch is cleared away.
But thatched buildings with medieval underthatch are still being discovered. "There may be some in Suffolk that remain to be discovered," says Letts. "There hasn't been any systematic survey. Many owners of thatched buildings simply won't realise what they might have because the underside is usually boarded over from below and modern thatch covers it entirely on the outside."
Surprises do occur though. Near Llandeilo in western Wales recently, Letts came across a farmer who knew of an isolated, long derelict farm building with blackened thatch.
But, because of the very different farming history of the area, the thatch consisted of a base of bracken, a layer of rushes and blackberry stems, and a top layer of wheat straw full of corncockles, cornflowers and other plants, knotted into bundles and entwined in the middle layer.
It is the first known building in Wales with smoke-blackened thatch. And it would not have survived if it hadn't long been covered with a corrugated iron roof to keep the
rain out. Letts believes that many local authorities are responding positively to the need to identify, document and retain old underthatch and that many thatchers are agreeing to retain it.
Doubtless, though, medieval underthatch is still being discarded, perhaps more out of ignorance than mendacity. But this incredible resource, a preserved history of farming and farm practices in the middle ages, is already as scarce as a corn marigold in a modern-day field of wheat.
To order a free copy of Thatch and thatching: a guidance note, call English Heritage on 0870 333 1181, or write to Customer Services, English Heritage, PO Box 569, Swindon SN2 2YR
