lightmaps look really bad

i have scene i wanted to lightmap. shaders are all standard, lightmap-resolution is 100 texels.
with realtime-lighting:



with lightmap:


aside from the blocky texture, the colors are strange. and the lightmap in the small tree gets white.
on a sidenote, i cannot select the lightmaps in the lightmap-tab. they are listed there and i see the scrollbar, but i can not...

lightmaps look really bad