I realise it's the direct translation, but in English I'm pretty much no one says "pruning the grass".
They probably don't say "podar a grama" in Portuguese either. At least that verb is not in my 5,000 word Portuguese frequency dictionary. Why doesn't Duolingo concentrate on the most used words?
As a horticulturist I have never pruned grass. Pruning involves the selective removal of limbs of shrubs and trees to enhance the plant shape, or improve conditions for better flowering, fruiting or general health. Grass I have cut, edged, trimmed and mown and just now I lost my heart by doing so.