During a recent visit ‘up north’ as a southerner would say, we visited several places along the Hadrian’s Wall and I encountered Harebell numerous times. It was of course growing across the region in the low grassy moorland, but it was also growing directly out of or on top of the wall.
This beautiful and delicate looking little species is a rhizomatous perennial herb. It is however far from delicate in its requirements, being quite tolerant of dry, open, and infertile habitats. It is also not too fussy about soil pH being found in both mildly acidic and alkaline soils also it can tolerate some heavy metal presence. All in all it is well suited to life on walls but is also encountered in grassland, fixed dunes, rock ledges, roadsides and railway banks. It flowers from mid summer onwards.
Its scientific name is Campanula rotundifolia and it has several common names as you might expect, one is Scottish Bluebell but in Scotland they often call it simply Bluebell. It is not related to what the English think of as a Bluebell the one that grows in woodlands. It is the flower emblem of Sweden and the county flower of Yorkshire. 
One of the places we saw it on Hadrian’s wall was mile fort number 37. it is the next fort along from Housesteads. Not surprisingly these milecastles (small forts) were built at one mile intervals all the way across the length of the wall.
This artists impression of how Milecastle 37 would have looked is by courtesy of HUKBMBEAR Thank you.
When it was up and running it would have had housing for 20 to 30 soldiers and they would have remained on site also each garrison would have manned the neighboring turrets. The milecastle’s garrison was a border post as well as being defensive in time of rebellion. It would have allowed the passage of people, goods and livestock across the frontier, and it is likely that the milecastle acted as a customs post to levy taxation on that traffic. Could Scottish independence could see the reintroduction of modern day equivalents?
Between each milecastle there would have been two turret structures these were located approximately one-third and two-thirds of the way between the milecastles; all very neat and precise just like the Roman roads.
The two turrets linked to milecastle 37 are named 37a and 37b. 37a is at Rapishaw Gap and was probably demolished before the Romans abandoned the wall and the only evidence for it now is some earthworks which can only be appreciated from aerial photographs.
Turret 37 b at Hotbank Grag is still visible but it is just a stone studded earthen platform so not that impressive now.
There were 80 milecastles and 158 turrets.
Walls and Flowers 