In real life, does grass follow surface normal or vetical?

[anicg 12]

Try to scatter some grass and get it a bit accurate, but places that I reach are all flat. anyone lives in an area where you can see (photos are not enough) if the grass grows following the surface normal or just vertical like trees?

[Rence 9]

By looking at the attached image, it does look like it follows the surface normal. I'm assuming the longer the grass gets, the more "vertical". So maybe a blend of the two for a realistic setup.
Where the lower part of the grass follows the surface normal and as it gets longer, it begins to grow vertically. Just an idea, not sure if it's completely realistic.