Rubus spectabilis (Salmonberry) is a naturalised neophyte in the British Isles, having been brought here from North America in 1827 by the Scottish Botanist David Douglas. It was first recorded in the wild in 1874 and is now found in many parts of Scotland, especially around Glasgow, Edinburgh and Aberdeen. I therefore consider it a worthy subject for study by our Urban Flora Project!
Rubus spectabilis (Salmonberry) in full flower. Image: ©Richard Milne
It is a member of the Rose Family (Rosaceae). Its morphology resembles blackberries and raspberries but is more like raspberries than blackberries, with prickles that are straight, not curved backwards. Its leaves are ternate, the leaflets are rhomboid, not circular like those of blackberries, and the serration of its leaflet margins more uniform in shape than those of blackberries, but diminish in size from the base to the apex of the leaflet. Leaves are a lighter (more yellow) shade of green than those of blackberries. The flowers are 2-3 cm diameter, usually solitary on lateral branches, so that the yield of fruit is rather small for the size of the plant. The petals are a rather deep pink, and the fruit when ripe is as large as a large blackberry and is orange/yellow in Britain (but often red in North America). The chromosome count of Salmonberry is the same as that of Raspberry, 2n = 14.
It is stated in Wikipedia that Rubus spectabilis is a deciduous, rhizomatous shrub growing to 1–4 metres tall and 9 metres wide. About 30-40% of the plant’s biomass is underground. Salmonberry shrubs sprout mainly from buds on rhizomes, stumps, and root crowns of the plant. It grows about 0.3–0.6 metres per year. It has perennial woody stems that are covered with fine prickles especially on new growth and it readily forms thickets, like many plants in the genus Rubus.
Images from the field. Left and centre: flowers (images: ©Richard Milne). Right: a fruiting branch (image: ©John Grace).
The leaves are alternate and trifoliate, 7-22 cm long with the terminal leaflet being larger than the two side leaflets. They are shed in late Autumn and Winter months, and the plant remains dormant or maintains minimal shoot elongation during the winter.
The flowers are produced between April and July. They are 2–3 cm in diameter, with five hairy sepals and five pinkish-purple petals that surround a cluster of stamens. They are bisexual with many (75–100) stamens and many individual pistils with carpels above the petals. They are pollinated by a variety of insects, perhaps mainly by beetles in the British Isles but in parts of North America hummingbirds are important pollinators. There are about 10 fruits per m2 and 17-65 seeds per fruit.
Salmonberries ripen approximately 30–36 days after pollination, from July to August in temperate climates. They are an aggregate of drupelets, 1.5–2 cm long, and resemble large shiny yellow to orange-red raspberries. The fruit pulls away from its receptacle, differentiating it from blackberries. In North America the fruits are polymorphic in colour, often either red or a yellow-orange. The red berries are more commonly consumed by birds, although this is probably not a strong enough selection pressure in itself to determine colour morph distribution.
Arrangement of flowers on the stem. Image: ©John Grace
A similar species from Japan, the red-flowered raspberry was once considered to be R. spectabilis subsp. vernus. It is now reclassified as R. vernus.
Much more information, from a North American perspective, is given by Oleskevich et al. (1996) or, alternatively, via this link. We learn that the name ‘salmonberry’ may derive from the natives’ fondness for eating the berries with salmon roe. One suggestion is that the berries resemble the salmon eggs themselves.
Here in the UK, Salmonberry is widely available from nurserymen, or by taking cuttings from existing material. The plants are perennial and prefer moist, even boggy, soil, and tolerate shade. The Edinburgh records are often from woods, parks and public places where they may have been planted, but there are other records by streams and rough ground that suggest dispersal by birds.
Examples of rather early fruit (Edinburgh, 8/06/23). In Rubus, many carpels are arranged around a cone-shaped receptacle and each carpel matures into a fleshy drupelet. Here, not all carpels have been pollinated, especially in the right-hand image. Note the colour contrast in the right-hand image. Both fruits came from the same plant but the one on the left is not fully mature and a paler shade of orange. Images: ©John Grace
The ripe fruit is slightly acidulous, and would make an excellent jam, but I have eaten all the fruit I ever found immediately! In North America it is likewise enjoyed by large mammals. Bears have been known to deposit 50,000 to 100,000 seeds in a single pile of faeces.
An American fan of the salmonberry extols it thus:
The species can be crossed with Raspberry, and it has been used in breeding raspberries for early fruiting and resistance to Phytophthora (Knight 2015). Native Americans have used it for food and medicine. The website of Plants for a Future finds many other uses, see here.
A hedge in a suburban garden, Edinburgh. The Salmonberry has grown vigorously and invaded the entire hedge. Image: ©John Grace
The distribution in the British Isles shows a tendency towards northern latitudes. Salmonberry is, rather strangely, almost absent from London and the south, but frequent in the Northern Isles (Orkney, Shetland) and on the North-East coast of Scotland. Likewise, the global distribution map shows it to be almost absent from southern Europe. It is clearly a northern species.
Distribution of Salmonberry in the British Isles. Left: before the year 2000, right: from 2000 to the present time. A slight increase is evident. Data: BSBI.
In Northern regions it does have the potential to become invasive, as recognised by a Risk Assessment from the National Botanic Gardens of Ireland (click here to view). Likewise, in Scotland, the Highland Council has shown concern for the threat posed to biodiversity. They say “this invasive plant has been present in Caithness for decades but is taking over large areas of woodland and hedging”. Once established it is hard to get rid of because it spreads by rhizomes (‘suckers’) which are difficult to dig out.
Salmonberry, global distribution according to GBIF.
If you grow this species in your garden, I would advise you to plant it in large plant pots, buried to within about 10 cm above soil level, from which it cannot escape!
References
Binggeli P & Paterson JPH (1995) Status and distribution of Rubus spectabilis Pursh in Ireland. Miscellaneous Notes & Reports in Natural History, Ecology, Conservation and Resources Management. http://www.mikepalmer.co.uk/woodyplantecology/docs/MNR-Rubus_specta.pdf
Knight VH (1991) Use of the salmonberry, Rubus spectabilis Pursh., in red raspberry breeding, Journal of Horticultural Science, 66:5, 575-581, DOI: 10.1080/00221589.1991.11516186
Oleskevich C et al. (1996) The biology of Canadian weeds. 105. Rubus strigosus Michx., Rubus parviflorus Nutt., and Rubus spectabilis Pursh. Canadian Journal of Plant Science 76: 187–201 doi:10.4141/cjps96-037
©Roger West
Botany in Scotland 
Very interesting. Happened to come across this plant in the car park of Glasdrum Wood, a National Nature Reserve. It took me a few minutes to work out what the plant was, but the flowers were distinctive.
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In Orkney this plant is the most serious invasive plant species and often germinates amongst areas of native willow carr, in other woodlands and on open hillsides and moorland. It is seriously difficult/ almost impossible to eradicate and is spread widely by birds, so appearing in more and more places and threatening valued habitats. I suspect in the northern coastal areas of Scotland, our maritime climate allows it to thrive unhindered by low winter temperatures (or grazing bears and moose!) A classic example of a plant that is likely in balance in its natural habitat in North America, but when removed to a new one like ours, is an absolute menace! I wouldn’t suggest anyone plants it.
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