C.-A. Hæggström’s research while affiliated with University of Helsinki and other places

Allium ursinum L. is a perennial bulbous herb of broad-leaved woods of Western and Central Europe. Of two subspecies subsp. ursinum is distributed in Western Europe including the Nordic countries. The general distribution of A. ursinum in the Nordic countries is outlined. The localities for A. ursinum in Finland are the northeasternmost in Europe. The rather few localities are concentrated to the Åland Islands (Al) and the archipelago of Regio Aboënsis (Ab). They are described in a chronological order of the first find in each municipality. Several localities with A. ursinum as a cultivated plant or as a garden escape are referred to. The habitat requirements for Allium ursinum are discussed. Although A. ursinum has a broad distribution with a clear tendency to occur as a weed, it is still a habitat specialist with a rather narrow range of ecological tolerance as it requires a mesic well-drained soil and drought as well as waterlogging seem to be unfavourable. A. ursinum is moderately calciphilic in the southwestern archipelago of Finland. Many of the accompanying species, 32.5 % of all species, are regarded as calciphilic. Allium ursinum has been used as a spice by man since ancient times. Many of its localities point towards a fairly strong hemerophilic tendency. Of the 53 localities in Finland described, 17-19 can be regarded as more or less natural, 30-32 as cultivated or otherwise introduced and 4 as uncertain, because of insufficient information. Therefore we regard A. ursinum as a moderately hemerophilic species. The dispersal of the seeds by autochory or by myrmecochory is discussed. A possibility for hydrochorous dispersal of seedling is referred to. A. ursinum is most probably going to be more common in the future due to introduction to gardens as both living plants and seeds are sold in garden shops. Further, the warming of the climate will be favourable for this in Finland southern species. As a strong competitor in the field layer, A. ursinum may become a problem in protected areas in the future.

The Åland Islands in SW Finland are known for their luxuriant vegetation with numerous calciphilic vascular plants. Ruderal plants are rather few compared to the adjoining regions of Finland and Sweden. However, new ruderal plants are occasionally found in Åland. We came across a ruderal site in the centre of the village of Godby, municipality of Finström, in 2002. Most of the organic topsoil had been removed and several rare ruderal species grew then on the open ruderal site. The site became more closed, resembling a meadow rather than a ruderal ground already in 2006 and later the vegetation developed into a tall and rough grown meadow with some shrubs and young trees. The following ruderal plants are treated more in detail: Agrostemma githago, Anthemis tinctoria, Centaurea cyanus, Cichorium intybus, Dianthus deltoides (cultivar), Echium vulgare, Holcus lanatus, Leontodon hispidus, Lotus corniculatus var. sativus, Papaver dubium subsp. dubium, P. rhoeas, Phleum phleoides, Rumex thyrsiflorus, Senecio jacobaea, Thymus pulegioides, Trifolium dubium and Vicia tenuifolia. Besides some trees and shrubs, 133 vascular plant taxa, most of them common in the Åland Islands, were observed growing in the ruderal site during the period 2002-2015. The origin of the ruderal flora is not known. It is suggested that at least some of the plants have originated from seeds in the former cultivated field. A deliberate sowing of flower seeds of foreign provenance cannot, however, be excluded, although we have not been able to prove it.

Echium vulgare L., chiefly a weed in the Nordic countries, was previously rather rare in the south part of mainland Finland and very rare in the Åland Islands. It has suddenly became much more common during the last twenty years. E. vulgare has been found in all municipalities of the Åland Islands, except Brändö. The reason for the rapid expansion of the species is partly road construction with possible introduction with grass seed mixtures sown on the newly constructed road slopes and verges, and partly deliberate sowing of E. vulgare along roads in the municipality of Lemland and perhaps elsewhere. A few cases of the species sudden appearance are described.

Chromosome numbers from a total number of 226 populations of Allium oleraceum were determined in Finland, Sweden and seven other countries. Two different chromosome numbers or cytotypes were found, tetraploids (2n = 32) and pentaploids (2n = 40). In Finland, samples were collected for chromosome counts from a total of 190 populations, which fairly well covers the distribution area of the species in Finland. The majority of the populations of A. oleraceum in Finland contained only one of the two cytotypes. A clear pattern in the geographical distribution of the cytotypes could be distinguished. The pentaploid cytotype predominates in the Åland Islands and in the archipelago of Regio aboënsis. The tetraploid cytotype predominates on the mainland of the Regio aboënsis and along the coast of the Nylandia. In south Häme, all studied native populations were of the tetraploid cytotype. Of all the studied populations in Finland 43.7% were tetraploid and 51.6% pentaploid. A few mixed populations with both tetraploid and pentaploid plants occurring in the same population were also found (4.7%). The chromosome numbers of 19 populations of A. oleraceum from the southern part of Sweden were pentaploids, with the exception of one tetraploid population. It seems that the pentaploid cytotype is predominant in Sweden, but no conclusions about a geographical pattern between the two cytotypes could be drawn. Based on the occurrence of the cytotypes, it is suggested that the pentaploid cytotype might have spread to Finland from the Swedish east coast via the Åland Islands to Kaland on the Finnish west coast and along the coast of Nyland to the archipelagos of Kotka and Hamina in Karelia australis. The tetraploid populations in south Häme are clearly connected to Iron Age activity and to old inland trade routes, and may be of eastern origin.

Epilobium hirsutum L. is an introduced species in Finland with the first reliable findings made in the late 19th century. The number of new findings accumulated slowly during the period 1900– 1929. From the 1930’s onwards, the number of findings grew rapidly and E. hirsutum has been found in 153 grid squares of 10 km × 10 km size in the southern part of Finland until 2012. The first information of the species in the Åland Islands is a note in the literature from 1821 and the first collected specimen in the Åland Islands is from the municipality of Sund in 1873. However, both these are doubtful as they were not noticed in Finnish vascular plant floras later on. The first reliable finding is from 1973 and thereafter the localities with E. hirsutum increased with four more during the 1970’s, eight new during the 1980’s, fourteen new during the 1990’s and 35 new localities during the period 2000–2013. It thrives chiefly in man-made habitats in the cultural landscape and the most common habitats in the Åland Islands seem to be roadsides and road ditches. Although E. hirsutum has expanded during the last fifty years in Åland, it is not common yet and it has not been found in most of the eastern archipelago area. As an immigrant in our flora, E. hirsutum is now well established in the Åland Islands and it will probably be more common in the future. However, it seems that it is not a harmful invasive weed in Åland.

Three species of the genus Aira, viz. A. praecox, A. caryophyllea and A. elegantissima, have been found in Finland. The geographical range of each species is outlined. Whereas A. praecox has been known since 1912 in the Åland Islands, A. caryophyllea was found as a new species for Finland on the mainland of Kumlinge, Åland Islands, in 2008. A. elegantissima has been found as an introduced plant (weed or sown as an ornamental grass) in five localities in different parts of southern Finland between 1868 and 1985. All seven known localities with their separate stands of A. praecox were studied in detail in the Åland Islands in 2009. Of these localities, one was found in 2005 and two in 2009. The accompanying vascular plants were noted and their calcium dependence was assessed according to previous studies. The accompanying species comprised 113 field layer taxa, most of them common in the Åland Islands. The majority of the accompanying taxa belong to the calcium-neutral group. However, 27 calciphilic species were found, about 24 % of all the accompanying taxa. The amount of calciphilic species was compared to previous studies in Åland. Soil samples, chiefly fine sand, from all but one of the seven localities were analysed for pH, exchangeable Ca++, Mg++, K+ and PO4-. Further, NO3- and NH4+ were determined and soluble nitrogen was calculated from values on NO3- and NH4+. The pH values of the soil samples were mostly rather low for the Åland Islands. The concentrations of exchangeable Ca2+, K+, Mg2+, PO4- and soluble N were also mostly rather low. A. praecox often grows by bathing beaches, and thus a possible way of dispersal is by bathers and campers, e.g. with blankets. The locality in Kumlinge seems to be on ballast brought ashore from a sailing ship long ago. Although A. praecox has disappeared in some stands in localities 1 and 2 in Eckerö, much larger stands and three additional localities are known today. However, A. caryophyllea may be endangered, as it is hitherto known in one locality only and the number of specimens was about 50 in 2009.

A small stand of Slender Rush or Path Rush, Juncus tenuis Willd., was found on trampled gravelly and stony ground at the edge of a car park on a path to café Soltuna on the hills of Geta (Getabergen). There were only 3 larger and 13 small tussocks of the species growing on approximately one square metre. The accompanying vascular plants were few; Agrostis cf. capillaris, Juncus effusus, Leontodon autumnalis, Plantago major subsp. major and Poa annua were the only taxa observed among the rush tussocks. Juncus tenuis was not seen during investigations of the vascular plant flora at Soltuna in 2003 and 2007. Juncus tenuis is introduced from North America to Europe and elsewhere. It is rather common in southern Scandinavia. It has been found in a few places in southern Finland from 1950 onwards; a somewhat uncertain find in the Botanical garden of the University of Helsinki exists from 1894. As Soltuna is a popular touristic place, it is suggested that Juncus tenuis was introduced at Soltuna with car traffic from Sweden.

The northern amphi-atlantic seashore sedge Carex mackenziei V. I. Krecz. was found by us in four localities in 2008-2011, two in Kokar and one in Brando in the eastern archipelago and one in Sund on the mainland of Aland. The hybrid C. canescens L. x mackenziei (C. x pseudohelvola Kihlm. ), which occurs regularly together with C. mackenziei, was found in Sund in 2010 and 2011. The general distribution of the two taxa is outlined. The previous finds of C. mackenziei and the hybrid in the Aland Islands during the 19th and 20th centuries are referred to. The future of Carex mackenziei and its hybrid in the Aland Islands is discussed.

The Arctic Bramble, Rubus arcticus L., was found in Gottby in the municipality of Jomala, the Åland Islands, SW Finland, in June 2009. It was both flowering and fruiting, although rather sparingly. This boreal species has not been observed in the Åland Islands since 1950. The total distribution of the species is outlined. An account is given of the pre-vious six observations of R. arcticus in Åland. The dispersal of the seeds (endocarps with seeds) of R. arcticus is treated.

The Wood Stitchwort (Stellaria nemorum) is common in most parts of Scandinavia and Finland. However, until now only two finds, one in Sund and one in Hammarland, are known from the Åland Islands. We found it on a new locality in Sund in 2008. Stellaria nemorum grows along a brook where vegetative shoots only were seen. We re-visited the locality in Hammarland, but the species could not be found by us. We noted that these two localities are similar, with moving soil water. The soil of the new locality was studied for pH and exchangeable macronutrients. The accompanying vascular plant flora was annotated. The dispersal of S. nemorum and the common species S. graminea and S. media is briefly discussed.