Some of the library plants created by Eric Linden track the terrain, for example

Leafy ground cover

Grass - short 1

Grass - short 2

Grass - tall 1

Grass - tall 2

The above also track the terrain as it is moved, which is simply fabulous.

I believe it would be a useful feature to allow the creation of custom ground cover that was able to use this system rather than the current mechanism of having to manually create a mesh that follows the contours only to have to re-do or hack something else in if the land needs to be changed.

I'll admit I was 6001 days old before I realised this when I decided to decorate some ground with Linden plants to match the surroundings!