http://www.mangago.me/read-manga/puchitto_hajiketa/ this one maybe?
http://www.mangago.me/read-manga/mankai_darling/mh/v01/c001/7/ maybe this one?
I know only this one that sounds a bit similar http://www.mangago.me/read-manga/kare_otoko_ni_izumi_o/
but the hair colors are the other way around. o_o
I know that manga :)
I don't remember, but I'll try to give details in case someone remembers,
The dude aka seme, (Who lost his memories) can speak to plants. His hair turns black when he loses his memories is due to him being unable to speak to plants. The uke, is a designer (I think) he recently got divocreced and the plants in his home are dying which comes in the seme. The seme helps the uke take care of the flowers and along the way the uke fell in love.
Hope that triggers someones memories, if this sin't the manga your looking for, I apologize
I don't think this is the one, but I thought I'd tell you :)
http://mangafox.me/manga/barairo_emperor/
I think this is what your looking for. Maybe?
http://www.mangago.me/read-manga/kare_otoko_ni_izumi_o/
I'm looking for this yaoi manga that I forgot TT-TT..
The Uke has a blonde hair (I think?)
The Seme has black hair
The seme love plants,I think he gave the uke one,
(FORGOT ALL OF THE SCENE, and all that I remember is..)
The seme has forgotten the uke (forgot why),
and he has this weird white hair?
the uke decide that it's okay (that the seme forgot him) for the both of them because I think he is afraid of falling in love? I also think that he run away from the seme >__< sheez,
Em sorry for this little bit of information TT-TT