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In order to elucidate physiological factors involved in causing the winter injuries of Ophiopogon japonicus and possible preventive measures against the disorder, the present studies were conducted with experimental treatments of plant-shading and root-cut. The chlorosis increased up to 100% in the plants treated with root-cut and non-shading. The plants covered with white cashmere showed only 16.4% of chlorosis. When the plants were not mulched during winter, their growth in the next spring became poor. The physiological vitality (by triphenyl tetrazolium chloride test) and chlorophyll contents of shaded Ophiopogon japonicus were higher than the non-shaded, and it indicated that shading is very important factor for growth in winter. Sugar, total protein and pigments (anthocyanin, carotene, and xanthophyll) contents were very low in non-shaded plants and photoinhibition may occur by full sunlight. The winter injury of Ophiopogon japonicus in the central and northward region of Korean peninsula might largely be caused by water deficit brought about by strong light. It can be effectively prevented by shading them, especially white cashmere covering decreased light intensity down to 40%, and effectively maintaining the temperature around plants. When planting Ophiopogon japonicas as ground-cover, it must be considered to select ideal places like shade of buildings for growing and appropriate mulching materials.
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