hair and join objects

hi, i’m trying to put a beard on my character, but when i join the objects, the beard goes all weird and stubbly, and the emitter becomes visible.

i made a small beard root shaped object created the beard with the partical emiter and it all looks good. but as soon as i attempt to join it to the face of my character object it stops being hairy.

how can i join the objects but keep the hair partical things rendering properly?