Worcestershire Record No. 26 April 2009 pp. 17-19

Bert Reid

When botanists talk about change, the emphasis is normally on plants or semi-natural habitats that have been lost or are in serious decline. There are many examples in Worcestershire of local extinctions or once common plants becoming rarities in unimproved grasslands, woodland, heathland, wetlands and arable areas. When discussion turns to plant increases the tone is still usually negative, with worries about the effect of about invasive aliens like Indian Balsam Impatiens glandulifera, Rhododendron Rhododendron ponticum, New Zealand Pigmyweed Crassula helmsii and Japanese Knotweed Fallopia japonica. But not all news is bad news, and while the damage to our tradition flora is undeniable it is important to recognise the positives. There are now more species “in the wild” in Worcestershire than ever before, and this is a good opportunity to welcome the newcomers and to celebrate their contribution to our flora now and in the future.

The gains and increases in our flora far outweigh the losses and decreases and it has been very difficult to select the species to cover here. Those I mention are a personal selection of those which have changed the expectations of local plant recorders since the start of the Flora Project in 1987 or that I think may do so in the near future. Other botanists would certainly produce different lists and I could easily have tripled the number of species included or selected different examples.

I have split the selected plants into six groups, and for each species give indications of the rate of increase by showing the number of tetrads recorded up to the end of 1986, 1997 and 2008. The groups are not natural groupings based on geology, soils, history and land use but are more related to the sources and causes of increase. A number of plants could have appeared in more than one group and some have been forced into a group when they could have had a group to themselves.

In Worcestershire, as in many areas of the country, the large-scale use of salt on roads in winter has created an inland habitat with conditions similar to the upper levels of coastal saltmarshes. Although this new inland habitat is very narrow, it stretches for great distances as a connected ribbon, allowing newcomers to spread across the country and the county. The first three plants listed here show the most extraordinary change in our flora since 1987. Danish Scurvygrass was first at Stoke Works in 1977 as a casual, but from 1989 it appeared on the M50 motorway and from 1990 rapidly spread to M5 and major trunk roads. It next reached other main roads and finally even minor roads – a recent record was from a house drive in a small urban cul-de-sac. Reflexed Saltmarsh-grass and Lesser Sea-spurrey both had earlier records from salty areas around Droitwich but have since followed much the same pattern as Danish Scurvygrass, although not yet reaching many minor roads. The Grass-leaved Orache and Sea Fern-grass have not taken off yet but might. Other plants have appeared in this habitat outside the county and should be sought for here. Common Scurvygrass Cochleria officinalis may already be here on the M5, but collecting a specimen for checking here is both illegal and dangerous! Sea Barley Hordeum marinum, Hard-grass Parapholis strigosa and Sea Pearlwort Sagina maritima are all potential newcomers apparently increasing on inland roadsides elsewhere.

These are a rather mixed bunch of plants, only connected by their appearance on road verges that are not necessarily salted. Buck’s-horn Plantain does appear on salted roads, but the early records were mainly on sandy commons. The recent increase is on road verges both salted and not salted, and it is not clear why the increase has occurred. Narrow-leaved Pepperwort was previously found on wasteland, railways and by canals, especially Droitwich area . It is now becoming much more widespread on roadsides. Keel-fruited Cornsalad was known only as a rare casual but is now our most common Cornsalad, by roads and is still spreading. Cornsalads can only be safely identified in fruit, and this plant could have been mis-recorded earlier, but the increase is nevertheless clear. The earliest records for Summer-cypress were as casuals, presumably garden escapes but for a number of years we have been aware of a northward spread along the M5 towards our area. In 2007 it reached a slip lane to Strensham Sevices and I will be surprised if it stops there. Early Meadow-grass has long been well known as a native plant on the south coast; it is now being found more generally and we have four recent records between Pershore to Evesham. As with several other plants, the mild winters associated with climate change may have facilitated the spread of this little grass.

In this man-made habitat a great many plants have increased. Guernsey Fleabane spread from the London area, reached Worcester in 1995, and is now increasing explosively. The related Bilboa’s Fleabane was found in Worcester in 1999 and 2005 and Yardley Wood in 2007. It may well spread. Other Conyza species such as C. bonariensis are perhaps even more thermophilic but may follow later. Narrow-leaved Ragwort is now starting to take off in Birmingham and could easily spread from the urban environment along man-made corridors of roads, railways etc. Hoary Mustard has show a significant national spread on wasteground and this spread has been mirrored in Worcestershire. Common Amaranth is much increased on nutrient-rich waste ground: increasing eutrophication may be a cause here. Round-leaved Cranesbill was rare but is now relatively common and widespread as part of a national northward expansion. Climate change seems a likely reason. Yellow-juiced Poppy shows a similar pattern but better recording may have had an effect. Shaggy-soldier only flowers after long hot summers but can persist as tubers. The steady increase on wasteland, arable etc. is surely due to the recent run of hot summers. Annual Mercury has shown no great change in overall distribution but has become much more common, filling in the gaps. Cockspur and Common Millet are just two of many possible examples of plants originating from bird-seed. This pair persist and spread more effectively than many of the other bird-seed plants.

Arable plants have suffered badly over the last fifty years from improved seed screening and ever more effective herbicides. Many of our arable plants are highly threatened. Rye Brome was a local plant of arable but almost disappeared in Britain post 1950. We re-found it in wheat fields by 1993 and it is now quite widespread in arable areas. The pattern of increase suggests introduction with crop-seed but our experience is not general nationally with few other areas showing the same sort of increase. Awned Canary –grass has also increased but is used in game-bird seed mixes and now seems established in Worcestershire. Borage comes from many sources - garden escape, bird-seed constituent and minor crop and now seems much more persistent for poorly understood reasons. Purple Viper’s-bugloss was only a casual but there are a few recent records of good quantities in arable.

Almost any plant grown in gardens has the potential to escape into the wild by seed, vegetative spread or from throw-outs. An ever increasing number of plants are readily available to the gardener and each year provide new county records. I have just selected five plants out of many: garden plants that have become common and widespread in recent times. The Yellow-sorrels are both warmth-loving plants escaping from rockeries to lawns and then pavement cracks, wasteland, churchyards, other mown grasslands etc. They both show surprisingly explosive increases. The Bellflowers are commonly grown on garden walls and escape to pavements and wasteland but more slowly and less far. The Garden Lobelia is an example of seeds dropped from hanging baskets to germinate in pavement cracks and wall bases. This plant is now often persistent.

Least Duckweed is a recent addition to the British Flora, being first recorded in 1977. The first Worcestershire record was in 1982 and there has been a great spread since 1988. It competes well with other Duckweeds and is clearly going to become a common and widespread plant. Nuttall’s Waterweed is also showing major spread, in part replacing Canadian Waterweed. It is tolerant of eutrophic water and spreads vegetatively with great efficiency. Only female plants are found in Britain. The Pigmyweed is a more serious worry since it increasing distribution threatens good habitats such as pond vegetation on commons. Greater Dodder was apparently only a casual with scattered sites until discovered over good stretches of the Avon and small part of the Severn. It is rare example of a native wetland plant that has done well locally over the last 20 years.

Although most of the newcomers are non-native plants, on balance they should be welcomed. For better or worse, the mankind’s activities have become the main driver of change within our flora. The constant stream of new arrivals has brought many unusual plants from around the world to our doorsteps, adding much interest to plant recording in the county, especially in the towns and cities where most of us live. We must treasure and protect our semi-natural habitats and long-standing native plants, but we should also rejoice when new arrivals take over our ruderal environment.