Working on a neglected maple forest last week reminded me of Lee Wright’s warning about mondo grass in a previous newsletter. The under-plantings in this setting were totally overgrown and needed radical thinning or removal. Military grass, violets, miniature ivy and even Lonicera willingly vacated the pot, but not mini mondo grass which stayed firm and could not be removed so strong were its roots. It had formed a thick solid mat and only repotting will enable its removal.
While it looks attractive, it has a darker side as it robs your bonsai of water and nutrients. In severe cases, it can out compete the tree leading to serious weakening of or even killing the tree. As a stop gap measure until spring, the mondo was cut hard to slow it down but removal is the only real solution. If you must have mondo grass, remove it annually, cut the roots hard and only replace a small section. Your bonsai will appreciate it!