Another thing I have learnt while shooting cyanotype.

 Here is a scene I shot this afternoon:

Here is the same scene as a cyanotype (reflected, unwashed, and still a negative):

One thing really stands out for me - and that is how little the grass reflects UV. Here is a crop of the two images overlaid and scaled. There are some inconsistencies, due to the differing characteristics of the lenses, but you can see how little the unshaded grass is exposed.

And the shaded grass is almost completely unexposed. 

And, indeed, checking the research, I find that one of the lowest natural UV albedos is from grass, at 0.02. (https://www.tandfonline.com/doi/pdf/10.3846/1648-6897.2008.16.83-88)

So my little hypothesis appears to have been borne out by independent research, and a source of other information about things I cannot see when taking the cyanographs, which will help me plan future exposures.