Biology of Allium oleraceum

Allium oleraceum is a European  that has a southern distribution in Finland. It is quite common in the Åland Islands, fairly common in the southwestern part of Finland and common to rare in the rest of south Finland. Chromosome counts of A. oleraceum from more than 300 stands in Finland and nearby areas, have revealed two different cytotypes, tetraploids (2n = 32) and pentaploids (2n = 40). In a few places, both cytotypes can be found growing in mixed stands, or close to each other in the same stand. Pentaploid cytotypes are common in the Åland Islands and southwestern coastal Finland, whereas tetraploid cytotypes prevail in inland populations.

A. oleraceum is propagating both vegetatively by bulbils at the top of the scape, and generatively by flower and fruit production. The vegetative reproduction by bulbil formation is efficient in both cytotypes, and the number of bulbils formed is high. The bulbils drop to the ground in the autumn resulting in a high density of sprouting and dormant bulbs in the ground, and a high variation in the density of the stands. The generative reproduction is more frequent in the pentaploid plants than in the tetraploids, resulting in several fruit capsules per plant and fairly high seed production.

The first leaves of A. oleraceum are formed in the autumn, they remain green during the winter and resume growth during warmer periods. The risk of frost damage of the leaves must therefore be eliminated by formation of osmotically active substances. It seems that a significant part of the total yearly photosynthesis of A. oleraceum takes place during the winter and spring months. Therefore, A. oleraceum may benefit from warming winters through increased photosynthetic activity.

 

Selected publications:

Åström, H., Haeggström, C.-A. & Haeggström, E. 2015. Geographical distribution of Allium oleraceum cytotypes in Finland and Sweden. –Nordic Journal of Botany 33:120-125. DOI: doi.org/10.1111/njb.00521

Hæggström, C.-A. & Åström, H. 2005. Allium oleraceum (Alliaceae) in Finland: distribution, habitats and accompanying vascular plant species. –Memoranda Societatis pro Fauna et Flora Fennica 81:1-18.

Åström, H. & Haeggström, C.-A. 2004. Generative reproduction in Allium oleraceum (Alliaceae). –Annales Botanici Fennici 41:1-14.

Leaves of Allium oleraceum that have overwintered expand and new leaves are produced in spring.Inflorescences start developing in early summer. Photo: Timo Saarinen.Allium oleraceum flowers and produces bulbils in mid-summer. Photo: Timo Saarinen.Following senescence of leaves in late summer, new leaves start growing in autumn. The leaves retain their photosynthetic activity and even grow during mild spells in winter. Photo: Timo Saarinen.