ghItlhpu' Voragh, jatlh:
Actually qep’a’ 2016 produced something close to one of your desiderata: magh Klingon plant that most closely resembles grass (n) magh yotlh lawn (n) So I would say *{magh tIq yotlh} “field of long grass” for grassland, steppe, prairie, etc., though {Hatlh} might be better for open, uncultivated/unmanaged land.
Oh yes, I did know about those (and I'm grateful for your reminder of them!). I suppose I'm more thinking that we have {HuD} and {ngech} for hills and valleys, but for open flat land like a steppe or plain or prairie, I wasn't sure if {yotlh} would be appropriate, since KGT seems to imply that it's a cultivated plot of land: "The verb {yob} ("harvest") is used to refer to gathering up plants or plant parts, whether from a field ({yotlh}) that has been sown or out in the wild." (KGT p.89) I've been using {Hatlh} as a stopgap, but it'd be nice to know what the semantic range is on these words. QeS 'utlh