Here are a couple of plants that we noticed for the first time this year. They are both members of the Daisy family and they both arrived on our shores in the 1700s. However the way that they came here was very different, the first arrived accidentally but the second was brought here on purpose.
Conyza canadensis - Canadian fleabane
Two specimens turned up growing close up by what we call the Queen apple tree. This fleabane is a plant originally native to North and Central America, where it has become a problem weed in soya bean fields and it is known there as Horseweed. Here with us it has a rather unassuming look, a tallish weedy annual growing in arable land and having very small colourless flowers and fluffy seed heads. It isn’t a problem in the UK. It also thrives in man-made environments such as the pavements in city streets. It can now be found from Cornwall right up to Scotland, and it seems to have spread rapidly north in recent years perhaps as a result of the warming climate.
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Canadian Fleabane:
leaves, flowers and seed |
In former times, it was used medicinally by the Native Americans. The crushed flowers could relieve nasal congestion and the prepared leaves were used to treat sore throats and dysentery. It is said that the seeds were first imported into the UK almost 300 years ago in the stuffing used by taxidermists to mount bird skins. It was later seen growing on walls in London in the early 1800s. Smoke from the burning leaves was said to kill fleas and lice, hence the British name. By the 1940s it had spread and was growing in much of England and Wales. A large plant can produce some 200,000 seeds and they have been shown to remain viable in the soil for at least 20 years. This seems strange as in dry storage conditions they only last 2-3 years, the wonders of nature.
If its strange journey to the UK wasn’t enough of a story, here is Canadian fleabane’s real claim to fame. In the USA this little plant has the distinction of being the first weed to have developed resistance to the powerful weedkiller Glyphosate (Roundup), which it did some twenty years ago in 2001.
Senecio squalidus - Oxford ragwort
At first glance this bright yellow-flowered species would not appear to have travelled very far to reach Chinnor, assuming it came from Oxford. However, life is not quite so simple!
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Oxford Ragwort:
flowers and seeds |
It has a wonderful tale to tell connected to the coming of railways in Victorian England, specifically the advent of the Great Western Railway (GWR). Even now it is possible to take a ride past the Orchard on a gleaming steam engine with the GWR markings proudly displayed. But to begin with we need to go back to around 1700 when plant-hunting botanists were exploring the slopes of Mount Etna in Sicily. They returned with Ragwort plants and eventually some were planted in the Oxford Botanic Garden, a garden which is even older than the one at Kew. Otherwise it might have ended up being called London ragwort I suppose.
Sometime later plants escaped from the garden and established themselves locally in and around Oxford, growing on stone walls and the college buildings themselves. Apparently some even took root on the Bodleian Library building.
Like the Canadian fleabane, Oxford ragwort has feathery seeds similar to those of dandelion (see photos) and they can spread a long way on the wind. But still it did need a suitable habitat to grow on, and it did not spread very far at first.
Stage two of its great escape came with the GWR in the 1840s. The clinker and stones used as the bed for the railway sleepers proved ideal for it to grow on. It was given a new environment that matched its former home on the lava slopes of the volcano. Probably it was helped by having no competition there from our native species. It quickly spread along the lines especially to the west of Britain. Stage three happened after WW2, when German bomb sites gave it a new opportunity to spread to eastern Britain. It can now be found in Scotland too. Finally it adapted to growing on the soil of any convenient waste land, such as might be found in our Orchard. And of course we are an easy ‘breath of wind’ away from the railway line.
It is a vigorous plant which is typical of hybrids. Indeed it comes from a hybrid between two different species that grow on the Sicilian mountain. They occur at either higher or lower altitudes but there is enough of an overlap to have allowed hybridization to happen naturally. The original collections were made in the hybrid zone but since the successful plants first escaped, they have altered so that they are no longer the same as the original hybrids or their parents. This is how they have come to be a separate species. It is known as a ‘neonative’, one that first arose here in Britain, so in a way it can be counted as a native plant. Its exact method of origin is not yet fully understood. In fact scientists at Oxford are still researching the evolution of these Ragworts, in collaboration with Naples and Bristol Universities. This surprising plant has become a model for studying how wild plant populations evolve.
As we continue to manage the Orchard site, who knows what will be revealed in 2024?
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Great Western
Railway Engine at Chinnor |
What is a native plant species?
To be considered native a plant has to have arrived here by itself, that is without human intervention, around 8000 years ago when we were still connected to the mainland of Europe. We later became an island when the Channel was formed, and only plants already growing here at that point are now considered UK natives.
A worrying report published last March showed that there are now more ‘alien’ species of plant in Britain than native species. Moreover, half of the natives are in decline. Looking at the Orchard surveys that we have been doing since 2021, there are certainly some ‘newcomers’ to be found here such as Verbena ‘Bampton’ and the Mock Strawberry. Scientists at Kew responded to the report in June and suggested that the worries about non-native species may be unfounded. Certainly it is only a very small percentage that are seriously invasive. In fact many aliens are actually beneficial to our struggling bees, blooming when native nectar is scarce.
When time allows I will look into the 90 or so species we have recorded and count how many are native.
See article below for a very interesting blog from Kew about the myths and complexities of ‘native’ versus ‘alien invaders’ and showing that the worries about the aliens is somewhat ‘exaggerated and misplaced’.
‘UK native’ plants and fungi, the meaning, the misconceptions and the science. Published 28 June 2022 at growwild.kew.org
Photographs © Christine Davis
Other sources used:
Botany in Scotland at botsocscot.wordpress.comGarden Organic at gardenorganic.org.uk
Natural History Museum news ‘Over half of British plants species are now non-native’ at https://www.nhm.ac.uk/discover/news/2023/march/over-half-britains-plant-species-now-non-native.html
(This information was picked up by the Daily Telegraph and the Metro which was where I first saw it)
Oxford Plants 400, Senecio squalidus at herbaria.plants.ox.ac.uk
Ragwort Facts at ragwortfacts.com
The Oxford Ragwort at obga.ox.ac.uk
Wikipedia
Christine Davis October 2023
Oxford Plants 400, Senecio squalidus at herbaria.plants.ox.ac.uk
Ragwort Facts at ragwortfacts.com
The Oxford Ragwort at obga.ox.ac.uk
Wikipedia
Christine Davis October 2023
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