"Palynology supports ‘Old Norse’introductions to the flora of Greenland" by Schofield, Edwards. Erlendsson and Ledger (2013) takes up this question and answers it affirmative: yes, according to their pollen research, some plants did not occur until the Norse colonists settled in Greenland. In a table (above) they show how, through the ages, ever smaller numbers of plants were suspected to be invasive. Their research is for only three plants: Rumex acetosella (sheep's sorrel), Polygonum aviculare (common knotgrass) and Achillea millefolium (common yarrow) which is perhaps not much but still fascinating. These are plants that are weedy almost everywhere but the Norse connection still makes it something magical. The conclusion from the paper:
In this paper we have demonstrated the utility of integrating pollen-analytical data from a network of sites as a series of maps in order to add an objective historical perspective to a long-standing debate over which plants were introduced to Greenland by the Norse settlers. A convincing case has been shown for three taxa – Rumex acetosella, Polygonum aviculare and Achillea millefolium. The patterns that have emerged from this exercise, particularly those for R. acetosella, appear to open wider debates related to the pattern and character of the Norse colonization of Greenland. For example, were there key differences in the function/role of some ‘farm’ sites that led to the creation of more favourable habitats for ‘Old Norse’ flora in some locations relative to others, and could differences in the patterns of colonization and the spread of ‘Old Norse’ elements in the flora of Greenland be accounted for through the initial introduction of these plants at only a few key sites? Palaeoecology may be able to pose but never fully answer these questions. A next step would be for geneticists to try and advance this debate by exploring the links between the floras around the Norse farms of western Iceland (or further afield), and those sites in Greenland where it is believed that the first settlers disembarked around ad 985.