Nitrogen fixing plants native to Scotland includes

Alnus glutinosa (Betulaceae)

Cytisus scoparius (Fabaceae)

Thank you so much Arvind!

Dear Matthew,

There are only four plant species endemic to Scotland but none of them are nitrogen fixing. Please have a look at this link for details.

https://en.wikipedia.org/wiki/Flora_of_Scotland

Good luck

Common Restharrow Ononis repens

Another widespread native Nitrogen-fixing plant (beside all the Fabaceae and Alnus) is the bog-myrtle (Myrica gale). Needless to say, the N-fixers aren't the plants themselves but their microbial symbionts.

i think Alnus sp.

Dear Matthew,

There are many members of the Fabaceae that are nitrogen-fixing in Scotland. http://livingfield.hutton.ac.uk/science/5000years/plants/legumes

@ Matthew Clare

Please also have a look at this useful RG link.

Article Nodulation and ecological significance of indigenous legumes...

Thanks!

Article Biogeography of nodulated legumes and their nitrogen fixing symbionts

https://www.permaculture.co.uk/articles/nitrogen-fixing-species-agroforestry-systems

http://www.livingfield.co.uk/living-field-garden/living-exhibits/legumes/

Article Nitrogen fixation by lichens in Scotland