This week’s plant will be familiar to anyone who has a garden with a herbaceous border. We are at a critical point where a well-know species is escaping the comfort of its many garden residences and ‘going wild’. But do not be alarmed, it is unlikely to ever become an invasive pest; rather, it looks like becoming a benign alien that will become a familiar part of our urban flora.
Inflorescence visited by butterfly (Large White, Pieris brassicae). Image: Chris Jeffree.
Verbena bonariensis is a South American plant that reached Britain in 1726. It was first grown in a private garden at Eltham (in south-east London) using a few seeds taken from a dried specimen collected in Buenos Aires, Argentina. The Eltham garden belonged to William Sherard, a plant collector who travelled around Europe and endowed a new Professorship at the University of Oxford called the Sherardian Chair of Botany. Other Verbena species from South America came to our shores later, but V. bonariensis is the one we find in nearly every garden centre. It’s a pretty plant, with many purple flowers on a long (up to 1.5 m) stiff stalk, often seen swaying in the breeze when celebrity gardeners appear on the TV.
Structure of the inflorescence. Note ridged hairy stems. Image: Chris Jeffree.
No doubt the seeds were shared with other 18th Century gardeners, and perhaps they were available commercially when seed companies developed their businesses in the middle of the 19th Century, reaching out to the public. Escape of this species and many others from gardens must have become commonplace in the 20th Century; and in 1949 V. bonariensis appeared ‘in the wild’ in Bristol.
Flowering head, with flowers and seed capsules. Image: Chris Jeffree.
In truth, we cannot be sure that Sherard’s garden was its single origin – it is also likely that more seeds came in later, stuck to imported wool from Argentinian sheep, and therefore multiple introductions are likely.
It is a perennial plant that survives average winters but is killed if the winter is severe. Its dense pattern of distribution in the southern half of the country is surprising, as central England can experience very low winter temperatures. I tried to find information on the climate of its homeland in Argentina. I found data for La Peregrina Mountain range, in Buenos Aires province. The mean annual temperature is 14 °C, with maximum temperatures reaching 32 °C, and minimum temperatures around 0 °C. In winter, frosts occur and sometimes it snows. The annual rainfall is around 850 mm and although the rain are distributed throughout the year they are most intense in winter and scarce during the summer. Oxford’s mean annual temperature is around 11 °C and the rainfall is around 700 mm, not exactly the perfect match with the homeland of this plant. What about Scotland? Glasgow’s rainfall is wetter, and the average temperature is lower, but the milder winters may suit the plant.
Inflorescence in winter, seed capsules remaining. Presumably the seeds are shed when the stems sway in the wind. Perhaps they are visited by small birds, but the seeds are tiny (see below). Image: Chris Jeffree.
I have seen V. bonariensis growing in southern England, along the edges of pavements and on derelict land. I’ve spotted it along an urban street in Yorkshire. However, in our Urban Flora of Scotland project it has been recorded only six times, always in or around Glasgow.
Seeds of Verbena bonariensis. They are about 1 mm long. Image: Chris Jeffree.
We may explore its recent distribution using BSBI/Maps. In the map below we show the spread from the year 2000 until 2025. The ‘jump’ to Scotland, Wales and Ireland suggests distribution via the many garden centres, with occasional escapes from gardens, and survival being aided by the milder winters we have been having lately. The distribution we now see probably could not have been sustained without a continuous supply of plants from the network of garden centres, because there have been some severe winters in the ensuing 25 years which would have wiped out local populations. We plan to look at this more closely, on a year-to-year basis, to see whether disappearance occurs in the year immediately following severe winters.
Remarkable increase in V. bonariensis records since 2000, from BSBI/Maps. Although recording ‘effort’ increased in the years up to 2020 in preparation for Atlas 2020, we believe the general pattern is ‘real’: consolidation in England and appearance in Ireland, Scotland, Wales.
The largest of our cities, Edinburgh and Glasgow, are home to hundreds of alien species. Grace (2025) found that about half of all the species recorded in these busy locations were introductions, many of them originating from the first half of the 19th Century. In those early days, every well-to-do gardener who saw Himalayan Balsam, Giant Hogweed or Japanese Knotweed growing in the botanic gardens would want their own. Seed companies sprang up, like Sutton’s Seeds in Reading, 1806 and Dobbies in Renfrew, 1865. No-one realised at the time how these splendid plants would eventually cause so much trouble to remove and be demonised as ‘thugs’ or ‘trifids’.
Verbena bonariensis is not thuggish. It is currently surviving as a benign alien in some parts of Britain. Further spread may occur as winters become warmer and it may become common along our Scottish pavements and in our parks. If so, its nectar will provide much-needed fuel for our pollinators, and some of these flying insects will prove food for birdlife. We should not complain about alien plants in our towns and cities – rather, we should teach our children the names of all the plants we see, and we should certainly protest when Local Authorities attempt to eradicate them.
References consulted
Cornwell I et al. (2025) Sown and self-seeding species in planted wildflower meadows increase floral abundance and richness in a Scottish semi-natural coastal grassland. Plant Ecology & Diversity 18, 249-266.
Echeverría ML et al. (2017) Survey of the vascular plants of Sierra Chica, the untouched area of the Paititi Natural Reserve (southeastern Tandilia mountain range, Buenos Aires province, Argentina). Check List, 13(6), 1003-1036.
Grace J (2025) The remarkable species richness of the urban flora of Scotland. Plant Ecology & Diversity, 18, 317-330.
Hicks DM et al. (2016) Food for pollinators: quantifying the nectar and pollen resources of urban flower meadows. PloS one 11, e0158117.
Morcelle, M et al (2012) Stem and leaf anatomy of six species of Verbena native to Buenos Aires province, Argentina. New Zealand Journal of Botany 50, no. 1 (2012): 3-14.
Salachna P and Piechock R. (2016) Effects of sodium chloride on growth and mineral nutrition of purpletop vervain. Journal of Ecological Engineering, 17(2), 148-152.
Woodward FI (1997) Life at the edge: a 14-year study of a Verbena officinalis population’s interactions with climate. Journal of Ecology 85, 899–906.
©John Grace
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