I can find no reputable reference for Diplacus grandiflorus 'Maximus'.
Erythranthe guttata 'Maximus'
There is a series of hybrid Erythranthe (formally Mimulus) that is called Maximus but isn't listed on our database.
http://floranova.com/products/...
I suspect that the name got messed up when the Mimulus genus was broken up.
All of the images posted under this entry look consistent with the Erythranthe Maximus series.
@zuzu
@Calif_Sue
