Short description of Spiraea salicifolia agg., Spiraea Bridewort group

The aggregate is poorly understood and has been much confused but is currently thought to comprise about 8 very similar species and their hybrids. All are suckering deciduous shrubs, growing 1-2m tall. They have entire, toothed hairless leaves and dense clusters of pink or white flowers 5-12 mm in diameter are borne in summer at shoot tips.

Impact summary: Spiraea salicifolia agg., Spiraea Bridewort group

Well established plants sucker vigorously and the resultant dense thickets exclude native vegetation and alter ecosystems.

Habitat summary: Spiraea salicifolia agg., Spiraea Bridewort group

Most frequently naturalised in hedgerows but also found in waste ground and other places as a result of garden throw-outs.

Overview table

Environment	Terrestrial
Species status	Non-Native
Native range	Middle Europe, Southeastern Europe, Eastern Europe, Mongolia, Kazan-retto, Nansei-shoto, Ogasawara-shoto, North Korea, Sakhalin, West Siberia
Functional type	Land plant
Status in England
Status in Scotland
Status in Wales
Location of first record
Date of first record	Unknown

Origin

Native to Central and Eastern Europe eastwards into parts of Russia, China and Japan. It has also been described as native to North America (USA and Ontario, Canada) but it is likely that those plants are a different species.

First Record

Distribution of naturalised species and hybrids of Spiraea is poorly understood because of obscure taxonomy and confusion between related species. However it is thought that true Bridewort (S. salicifolia s.s) had naturalised in GB by 1805.

Pathway and Method

Bridewort (S. salicifolia s.s) was introduced to cultivation by 1655. Numerous species and hybrids have been introduced into cultivation as an ornamental and at least some of the British naturalised populations are now thought to be of the hybrid S. x pseudosalicifolis (Confused Bridewort). In some places the aggregate has been popular as a hedgerow plant but many naturalised populations are likely to have developed from garden cast-outs.

Species Status

The BSBI Maps Scheme shows Bridewort scattered across the British Isles and present in 354 10 km grid squares by 2009. It is unclear which taxa are included within this distribution as Stace (2010) does not recognise S. salicifolia agg. and furthermore states that the true species (S. salicifolia s.s) is actually very rare and likely to be extinct. The New Atlas of the British & Irish Flora lists S. alba, S. canescens, S. douglasii, S. media, S. japonica, S. salicifolia, S. tomentosa and their hybrids within the Spiraea aggregate. The Flora of Northern Ireland includes six similar species and hybrids within the Bridewort aggregate naturalised there. It seems however, there has been a steady increase in occurrence and range of naturalised plants over the last century and the aggregate is still spreading slowly. In Europe, Bridewort has been reported as naturalised in France, Germany, Italy, Norway and Sweden.

Dispersal Mechanisms

Plants in this aggregate spread by suckers and are likely to be dispersed to new sites through human activities as root-bearing fragments in soil and garden cast-outs.

Reproduction

Shrubs bear white or pink flowers in dense heads in summer – these are visited by insects but if seed is produced then there is little documented information about its viability in GB. Pollen fertility is given by the Plant Crib as one of the most reliable ways of identifying these plants – those of hybrid origin have infertile grains which are mostly collapsed and do not readily take up acetocarmine-based staining agent. Plants spread readily through vegetative reproduction, from suckers.

Known Predators/Herbivores

It is not known whether grazing animals or other herbivores will consume Bridewort, but mature stems are woody and possibly unpalatable. Plants are known to be afflicted by a number of sap-sucking insects including the aphid Brachycaudus spiraeae and mildews (Podosphaera clandestina and P. spiraeae).

Resistant Stages

Plants drop their leaves in the autumn and become dormant until spring.

Habitat Occupied in GB

Naturalised populations are normally found in hedges and on waste ground.

Together species within the aggregate are found in scattered localities throughout GB. There are particular concentrations in the Midlands, parts of Wales and Northern Ireland (Co. Tyrone).

Environmental Impact

Together species within the aggregate are found in scattered localities throughout the country. There are particular concentrations in the Midlands, parts of Wales and Northern Ireland (Co. Tyrone).

Health and Social Impact

There are no documented health and social impacts of this plant. Some species have a long history of medicinal usage as most or all parts of the plant contain salicylate compounds with analgesic, anti-inflammatory and fever-reducing properties.

Economic Impact

There is negligible information available about the economic impacts of Bridewort, although costs associated with eradication of plants are likely to be incurred by land managers and owners.

Identification

Rich, T.C.G & Jermy, A.C. (1998) Plant Crib 1998, Botanical Society of the British Isles.

Silverside, A.J. (1990) The nomenclature of some hybrids of the Spiraea salicifolia group naturalised in Britain. Watsonia, 18, 147-151.

Stace, C.A. (2010) New flora of the British Isles, Third Edition, Cambridge University Press, Cambridge.

Biology, ecology, spread, vectors

Preston, C.D., Pearman, D.A. & Dines, T.D. (2002) New Atlas of the British and Irish Flora, Oxford University Press, Oxford.

DAISIE European Invasive Alien Species Gateway: www.europe-aliens.org

Distribution maps from the BSBI Maps Scheme: www.bsbimaps.org.uk

Flora of Northern Ireland: www.habitas.org.uk/flora

USDA Germplasm Resources Information Network: www.ars-grin.gov

Management and impact

Southeast Exotic Pest Plant Council: www.se-eppc.org/manual/

General

BioInfo (UK): www.bioinfo.org.uk