Plant of the week – October 4th 2021 – Japanese Rose (Rosa rugosa)

This is not the rose of England, nor the ‘red red rose’ of Robert Burns and definitely not the red rose of Lancaster. It’s an Asian rose that has been repeatedly introduced into British gardens beginning in the 18th Century (when its name was Rosa ferrox or R. kamtchatica). Then, it was confined to gardens. In Britain it was first recorded in the wild from the 1920s following a re-introduction in the 1870s. Recently, its capacity to spread has become evident.

There are many species of wild rose in the British Isles. Stace (2019) lists 25 main species and numerous hybrids. Rosa rugosa is relatively easy to tell apart from the others from its rugose (rough) leaves, its many bristly prickles of unequal length and its large bright-red hips (2-2.5 cm) with conspicuous sepals. It forms dense bushes up to 2 metres tall. Its fragrant flowers are usually red but white forms are common and pink ones can be found.  Bean (1980) points out that this rose hybridises readily with other roses; potentially, this creates a problem in identification. Moreover, the repeated introduction of the species from different parts of its natural range will have added to the diversity within the British populations.

Prickles: numerous, of variable size and length. Photo: John Grace.

It became ‘naturalised’ throughout north-west Europe, propagating itself by the production of rhizomes with ‘suckers’ and by dispersing seeds in the faeces and vomit-pellets of birds, as well as being carried by tides and floods. Thrushes and pigeons are said to be most frequent bird vectors, with contributions from redwings, all being attracted to the large red fruits (rose fruits are called ‘hips’). The hips float in water for many days, and so do the individual achenes.

It has remarkable tolerance of salt. Although the plant has none of the visual characters of typical halophytes (fleshy leaves, waxy surface) an experimental watering of seedlings every day with sea-water-strength NaCl produced no symptoms of injury (Dirr 1978). Of the seven woody species compared by Dirr, it was the most tolerant. This salt tolerance allows the species to excel in coastal sites in Britain and along winter-salted roads and motorways in Scandinavia and Germany. It doesn’t mind sand, even thriving when occasionally sand-covered. For this reason it has been planted for sand stabilization and coastal protection.

Large red fruits (‘hips’) with extended sepals. Photo: John Grace.

However, in many countries the species tends to invade coastal dunes, threatening their biodiversity. In Great Britain, this plant is an Invasive Alien and prohibited under the terms of the Wildlife and Countryside Act of 1981. The definitive list of UK’s prohibited species is surprising hard to find but I eventually found it as Part II of Schedule 9 of the Act:

https://www.legislation.gov.uk/ukpga/1981/69/schedule/9#reference-c22562891

These are the species that you must not ‘plant or cause to grow’ in the wild. However, Rosa rugosa is easy to buy for your garden. You will find many internet suppliers who will tell you such things as “Rosa rugosa will add colour and wildlife interest into a mixed hedge”. But they do not tell you that if you plant it near the boundary, its suckers will ‘cause it to grow’ outside your garden and thence ‘in the wild’ and you will be breaking the law.

Its natural range is east Asia where it occurs predominantly as a coastal species on sandy and gravelly beaches, dunes and grasslands, in cool damp climates. According to Bruun (2005) the range is “from the Russian Far East in the north, including Kamchatka (to 55°N), Sakhalin and the Kurile Islands, Khabarovsk and Primorye, to northern Japan, including Hokkaido and Honshu (to 35°N) in the south, also the Korean Peninsula and northeastern China, including eastern Jilin (Hunchun Xian), coastal Liaoning and islands, and eastern Shandong (Yantai Shi), where it is classified as an endangered species due to over-harvesting”.

The over-harvesting in Shandong is for herbal medicine and perfume. The pharmaceutical properties have been described by Lu and Wang (2018). It has essential oils, flavonoids, polyphenols, polysaccharides, pigments and vitamins. In China, petals and flower buds are commonly consumed for production of jams, teas, pies, juices and beverages. Extracts of petals, hips and roots have been widely applied in China, Japan and Korea for treatment of diabetes, pain, anticancer and cardiovascular disorders. Its cultivation in China dates from 1100 AD (Bean 1980).

In western Europe its main use has been as an ornamental plant. As well as decorating gardens and forming hedges it is sometimes used as a rootstock by rose growers and breeders, but not so often these days because the joint between the rootstock and the rose has been found to break more often than with other wild roses.

A 60-metre stretch of shore colonised by Rosa rugosa at Ballantrae Bay, South Ayrshire. Photo: John Grace

It is perceived as a threat to coastal vegetation in Europe (Giulio et al 2020). It is hard to control. Digging can only work when all rhizomes have been excavated. Burning does not work- it comes back. Grazing by goats is reportedly successful, but then the goats become the pest! Systemic herbicide such as glyphosate does work but several applications are needed. Here in Britain, it is not yet at the stage to be considered an important threat except at a few sites (Smith and Deed 2019). In South Ayrshire I have seen masses of it, forming dense thickets and blooming from June to August. No-one minds, it adds colour and gladdens the heart; it reduces erosion of the coast. Often it is near to settlements suggesting that these plants are descended from ornamental plantings around houses and cottages, and perhaps to provide some garden shelter.

From a nursery catalogue 1902 (USA). https://upload.wikimedia.org/wikipedia/commons/7/75/Everything_for_the_garden_%2816668109789%29.jpg

My favourite recent research paper on Rosa rugosa comes from Belgium, where 96 woody species were grown at a common garden in Antwerp to see which ones were most effective at trapping urban pollution. The best of all was the Butterfly Bush, Buddleja davidii whilst Rosa rugosa was in sixth position in the pollution-trapping league table (Muhammed et al 2019). Evidently, invasive aliens do have their uses.

Rosa rugosa in Britain and Ireland. From the BSBI website.

The author of Rosa rugosa, Carl Peter Thunberg  1743 – 1828, was a Swedish botanist and physician, and a pupil of Linnaeus. He travelled to Japan at a time when the country was beginning to open up and collected plants and coins. He cured some people of syphilis which was known in Japan as ‘the Dutch disease’, and became famous. The usual vernacular name ‘Japanese Rose’ does not acknowledge its wider distribution. Bruun (2005) lists translations of names used in other parts of the world: Ramanas Rose, Turkestan Rose, Potato Rose, Saltspray Rose, Beach Egg-Plant, Sea Apple Blossom, Wrinkled Rose.

References

Bean WH (1980) Trees and Shrubs Hardy in the British Isles, Vol IV. Eighth Edition. John Murray, London.

Bruun HH (2005) Rosa rugosa Thunb. ex Murray Journal of Ecology · March 2005 DOI: 10.1111/j.1365-2745.2005.01002.x

Dirr, M.A. (1978) Tolerance of seven woody ornamentals to soil-applied sodium chloride. Journal of Arboriculture, 4, 162–165.

Giulio et al. (2020) Alien flora across European coastal dunes. Applied Vegetation Science 23, 317-327.

Isermann, M. (2008) Effects of Rosa rugosa invasion in different coastal dune vegetation types. In: Tokarska-Guzik, B et al. Plant Invasions: Human perception, ecological
impacts and management. Backhuys Publishers, Leiden, The Netherlands, pp. 289-306.

Lu and Wang (2018) Medicinal Components and Pharmacological Effects of Rosa rugosa. Records of Natural Products 12:6 (2018) 535-543.

Muhammad S et al. (2019) Atmospheric net particle accumulation on 96 plant species with contrasting morphological and anatomical leaf characteristics in a common garden experiment. Atmospheric Environment 202, 328-344. DOI 10.1016/j.atmosenv.2019.01.015

Smith PH and Deed B (2019) Japanese Rose (Rosa rugosa): its invasion and colonisation of the Seffon Coast, north Mersyside, UK. British and Irish Botany 1, 185-201.

Stace CA (2019) New Flora of the British Isles. C&M Floristics.

John Grace

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