Have grown the above plant for several years and always had plain green leaves.
Last year I noticed a self seeded plant which had attractively variegated leaves. Flowers exactly as normal.
Just out of interest, I saved and sowed seeds of this particular plant earlier this year and all the seedlings are already showing the variegation.
Having looked in my RHS book of plants, I don't see anything listed with a leaf variegation altho I haven't yet had time to check out anything online.
I wondered if anyone else grew these plants and have noticed a similar thing ?