Helsingin kasveja 7. Liitosalueen antia

Vascular plants of Helsinki 7. Contributions of the latest annexed area

As of 2009, adjacent land areas in Helsinki’s neighbours Sipoo and Vantaa were annexed into Helsinki. The land area of Helsinki increased by nearly 30 km2 and the water area by about 2,6 km2. The vascular flora of the annexed area was accurately mapped in 2011‒2015 as a supplement to the mapping of the former area of the city (land c. 187 km2, water c. 500 km2). Despite its relatively small size, the annexed area strengthened considerably the populations of many native or archaeophytic plant species in the capital of Finland by adding numerous new occurrences and often also by increasing the average size of the occurrences. Due to the basically forested and rural nature of the annexed area, the greatest winners of the flora include especially plants of the following environments: (1) slope groves and mossy heath forests, (2) open bogs and pine swamps, (3) oligotrophic inland waters, (4) tops and precipices of high rock outcrops, and (5) semi-natural grasslands. Only two species, viz. Filipendula vulgaris and Hypochaeris maculata, were gained as new to the all-time flora of Helsinki.