Sabrina, my scape height is 20" and bloom size is 5 1/2". I have large clump that started blooming yesterday. Always Afternoon was kind of fickle for me also. Bloomed great 6 years ago and hardly nothing the next season. Last year i moved it into newly prepared bed and started using Milorganite on all my plants. Its has grown and sprouted buds like never before as have all my plants for the most part.
I tend to take scape height as an average and bloom size is more accurate i think.
Sorry i do not grow anything quite like your bloom. But it is a pretty one.
