17 March 2001

Smothered to the brink of extinction

Some species of annual arable flowers are on the brink of extinction, and our conservation measures could be threatening them still further, reports Tom Allen-Stevens.

FOR years agronomists have come to your farm with advice on how to control your annual weeds. How would you react if someone else arrived who was keen on you preserving them?

It sounds like complete folly, but our war on weeds has been remarkably successful. So much so that the future for some species of arable weeds looks bleak indeed. The difficulty is that few organisations have accurately documented the scale of this decline, so how much of a problem it is can be hard to gauge.

This has been one of the aims of the Northmoor Trust. Based in Oxfordshire, the trust has been detailing the incidence of these weeds. "We prefer to call them rare arable flowers," says Northmoors Steve Gregory. He believes that many of the books and registers that document the incidence of these plants are hopelessly out of date. "If you look up a flower like the corn marigold, itll say its locally common. Local botanists and our own experience suggest this is no longer the case in Oxfordshire, however."

Surveys

So to gauge whether the plants still exist and where they are, the trust has carried out extensive field-by-field surveys, 50% grant-funded by English Nature. With the owners permission, the trusts researchers have studied arable farms along the Midvale Ridge – a limestone ridge that runs from Buckinghamshire to Swindon. Its light soils make it an area of high weed diversity.

The main species the trust is looking out for are 51 local annuals – those that complete their life cycle within one year and require some soil disturbance before seeds will germinate. Of these, 31 "A-list" species include those that are nationally scarce or so rare that they are listed in the British Red Data Book, which documents very rare and vulnerable species found in the UK. The remaining 20 species on the second list are more common, but believed to be rapidly declining.

But just how important are these weeds? "I suppose you could query whether they really are an important part of the native flora. Many have been imported over the ages – some dating back to Neolithic times – while others came over with the Romans. But this in itself gives them historical significance, while they are also an important food source: some plants provide a home for saw fly larvae, which are a valuable food for game chicks and other farmland birds."

They can also help you get grant funding. In areas such as the Midvale Ridge, rare arable flowers are a high priority on the local biodiversity action plan. If a high incidence of some of these flowers has been recorded on your farm, it may weigh in your favour when it comes to making an application under Countryside Stewardship.

For local Countryside Stewardship adviser Vicky Price, the value of these weeds should not be underestimated: "Some are very beautiful as well as being rare and we dont want them to disappear. Like all wild flowers, they are also an important food source for corn bunting and skylark as well as for invertebrates. You can liken them to our much-prized chalk grassland – both have developed through the long association between nature and the farming community."

Margins

Those growers who are joining the scheme in the area are encouraged to look out for them, especially if they have any lighter soils on the farm. In one case, Miss Price asked a grower to carry out a survey before advising on margin management.

But here lies one of the schemes apparent anomalies, as Mr Gregory explains: "A serious problem is the perennial margin. Planting six-metre grass strips is one of the actions encouraged under Countryside Stewardship. But these smother the rare arable flowers since their seeds are usually only found in the outer four metres and they need annual cultivation in order to germinate. Arable flowers are one of the key factors for Countryside Stewardship in this area. Were hoping that the scheme may change to encourage nurturing these plants."

This has always been the case according to Miss Price: "There is an option to establish a rare arable weed margin specifically to encourage these flowers. We also strongly encourage conservation headlands."

Rare arable weed margins consist of a six-metre uncropped strip which is cultivated annually or biennially, in spring or in autumn, depending on the types of plants found locally. Conservation headlands are usually established alongside six-metre grass margins. Herbicide use on these outer six-metre strips of the crop is restricted, although not banned completely. With careful planning and management, it has been shown that some rare arable plants can migrate from margins into headlands.

Stewardship would always be tailored to the field in question, however, points out Miss Price: "Rare arable weeds may be appropriate on thin, sandy or chalky soils, while permanent margins, with or without conservation headlands, may provide a better solution on richer soils or in weedier areas."

And you dont have to be part of a scheme to encourage the flowers, says Mr Gregory: "It doesnt take a big change in management to make a lot of difference. Just a slight reduction in herbicide use or nitrogen inputs can help many of these plants survive. When we survey we often find arable flowers surviving in the corners of fields where farmers have difficulty spraying."

Mr Gregory also supports the use of bare, uncultivated strips to encourage the plants, pointing out that trials in the Brecklands of East Anglia have proved quite successful. But in practice there are a myriad of problems to get over. Charles Flower farms 70ha (170 acres) near Marlborough in Wiltshire. Its an all arable unit, but in recent years he has established many small tree plantations and areas of wild flowers.

"We have six-metre headlands, two-metre headlands, a two-acre clay meadow and a five-acre chalk bank meadow. There is also a wild flower cliff where 150 wild flowers are set out and labelled." He also sells wild flower seed and runs workshops and nature trails so that growers can come and see how it works in practice.

"Relatively speaking, perennial margins are easy. But trying to look after rare cornfield arable weeds is difficult. Whether youre growing organic or conventional crops, the density of modern cropping is such that theres simply not enough room for them to grow. We have corn buttercups and have tried to encourage them in the field, but tying them in with a modern farming system is a nightmare."

So he has looked outside the main production areas to encourage corn buttercups and mousetail, for example in new tree planmtations or grass margins. "We make passes of the rotavator on the headland and broadcast some wheat into it. If you simply rotavate you get wall-to-wall pernicious weeds. But you have to be dedicated to make it work: its one thing establishing perennial strips. Its quite another carrying out operations every year to encourage a plant like mousetail than you can hardly see."