Ilex rugosa, the tsuru holly, is a species of flowering plant in the family Aquifoliaceae, native to southern Khabarovsk Krai, Sakhalin, and the Kuril Islands in Russia, and to eight mountain summits in Japan.[1] [2] It is usually quite prostrate (growing ever lower with increasing altitude) and does well in areas with protective winter snow cover to prevent damage from late frosts.[2]
Because of its cold-hardiness, Kathleen Meserve crossed it with Ilex aquifolium (common holly) and produced hybrids dubbed the "blue hollies" and later given the scientific name Ilex ×meserveae.[3] Two of these hybrid shrubs, sold as clones, have gained the Royal Horticultural Society's Award of Garden Merit.[3] 'Conapri' (trade name) is female.[4] 'Conablu' (trade name) is male and grows a bit taller than 'Conapri', perhaps at maturity.[5] [3]