Posted: 22/06/2012 at 15:06
Do you mean H. argutifolius or H. angustifolius? H angustifolius is probably H. viridis.
H. argustifolius is the one Jo4eyes refers to as 'the corsican one'. As he rightly says it may be cut down in very ealry Spring or later winter. Seed head can be removed about now, but they are short lived plants and it may be best to allow some seeds to fall, for replacement plants.