Viitapihlaja-angervo – Sorbaria sorbifolia

False spiraea is an erect, lush shrub in the family Rosaceae. It spreads by subterraneous runners and roots reach deep into the ground. In Finland, the false spiraea stock cultivated in the past had very poor seed production and it only propagated vegetatively. Today, stocks that produce seed are also available and their potential to spread is significantly higher.

False spiraea can grow 1 to 2 meters tall and form extensive stands. The large leaves burst in early spring and resemble rowan leaves. The are dainty pinnate with 6-15 pairs and the top of the blade is imparipinnate. The species blooms in mid summer, in July-August. The white-flowered panicles form inflorescences that can measure up to 30 cm long.

The false spiraea originates form the region stretching from the central parts of Siberia to Japan and the Kamchatka Peninsula, where it grows on riversides and coniferous swamps. It was introduced to Europe as an ornamental, but has since ran away from cultivation. Among other places, it is found as a fugitive on roadsides, wastelands and forest edges.

The false spiraea has proven to be an invasive species in several countries, including Sweden, Norway and Lithuania.

In Finland, false spireae thrives throughout the country, even in Lapland. It is quite unpretentious to the place of growth, but it grows and spreads faster in lush places. It has been found to spread even to protected areas.

Invasive alien species included in the national list (National list of alien species)

The false spiraea (Sorbaria sorbifolia) has nationally been regulated as an invasive alien species. It may not be released into the wild, imported into Finland from outside the EU or from other EU countries, transported, transferred, bred or cultivated, disposed of, passed on, sold, marketed, or otherwise handed over. 

After a two-year transition period, from 15th August 2025, the cultivation of the species will be prohibited .

False spiraea spreads by its subterraneous runners, and thus, local stands can be covering and spread strongly. In addition, pieces of runners thrown into a compost or a ditch may grow into thickets, which will be later laborious and difficult to dispose of. The dense stands covering the ground shade and block light from other plants, affect the composition and abundance of species, and reduce diversity.

In a Finnish study, some alien shrubs in the family Rosaceae (thicket shadbush (Amelanchier spicata), rugosa rose (Rosa rugosa) and false spiraea) have been found to have a clear effect on the vegetation beneath them: the number of species and moss cover were clearly lower under the alien shrubs than those of the native ones. On the other hand, there was more litter under the alien shrubs. The explanation for this may be that the chemical composition of the leaves of non-native shrubs is so different that our decomposer biota are not adapted to them. For example, the leaves and flowers of the false spiraea are known to contain large amounts of toxic cyanic acid, which contributes to slowing down the decay of leaves.

The false spiraea is challenging to eradicate. The species tolerates cutting quite well, but cutting the plant down to the ground every year can curb its spread. To ensure the eradication of the plants, the cutting down should be repeated 3-4 times during the growing season for several years. To enhance the eradication, rhizomes can also be dug out. In addition, the species can be controlled by covering the down-cut area with a thick tarpaulin or other cover. It is important to prevent the spread of false spiraea from the garden and courtyard into nature, e.g. by using a root barrier mat and/or by weeding and digging out suckers whenever they appear. Also, it is important to handle garden waste carefully to prevent the species from spreading with plant waste or soil.

As the species has nationally been regulated as invasive alien species, it cannot be imported, bred, sold or otherwise held, or released into the wild with the transition period of two years.

Do not buy or grow an invasive alien species. Ordering a false spraea online is also prohibited. It must not be handed over. Eradicate any invasive alien species in your garden and handle garden waste so that no seeds or plant parts capable of germination can remain vital. Make sure that the species cannot spread through soil material. Prefer domestic plants or plants that do not spread easily in your garden.

Professionals are obligated to prevent the spread of false spiraeas and its seeds and plant parts outside their area through dirt, soil or other plants.

Kim, D.K. & Zee, O.P. 2000. A new cyanogenic glycoside from Sorbaria sorbifolia var. stepilla. Chem. Pharm. Bull. 48:1766-1767.

Lanta, V. & Norrdahl, K. 2018. Different Germination Success May Explain Lower Species Richness of Herbaceous Vegetation Below Non-Native Than Native Shrubs. Annales Botanici Fennici 55(1–3), 7-15.

Lanta, V., Hyvönen, T. & Norrdahl, K. 2013. Non-native and native shrubs have differing impacts on species diversity and composition of associated plant communities. Plant Ecology 214: 1517–1528..