Grasses are like people - when winter's over they need a good cut and colour. There are various schools of thought on how to achieve this, and they probably all work.
But there's an inner hairdresser in all of us, so we each have our own, special styling tip. Mine is this: take your invaluable three-pronged cultivator tool and comb your grasses till they shriek. When there's a pile of dead hair as large as the remaining grass, the first part of your job is done.
Then find a pair of sharp, robust scissors. Unless you want your grasses looking like Grace Jones, don't cut them straight across the top. Employ the same technique as your hairdresser does when "texturing" your hair.
Hold a section of grass flat between your forefinger and third finger, and slice out sections of grass, moving the scissors from your fingers to the top of the grass. Take care not to nick your knuckles.
This technique gives the newly trimmed grass a natural look without any demarcation line. If you can't find your inner hairdresser, check out a couple of texturising clips on Youtube. And no matter how well your grasses turn out, best not to try this on your own tresses.