Yesterday, right at the side of the street, I had found a strip of land between two fields, that had been left as a wild flower meadow, and at the moment it is full of wonderfully blue flowers. As yesterday’s attempts had been completely fruitless, I decided to return today and try it again, this time not with the 85/1.8 but with the 18-200 at 200 mm. 
Seems like I was right. What you need in such a case is not shallow depth of field (it will be shallow anyway, don’t care), what you need is compression. Look for a lump of blue flowers, go near, shoot right through it onto some yellow or orange flowers in the middleground. That’s exactly what I wanted.
The Song of the Day is “Pleasantly Blue” from the 1992 4 Non Blondes album “Bigger, Better, Faster, More!”. Hear it on YouTube.