Drought tolerance of <i>Liriope graminifolia</i> (L.) Baker and <i>Ophiopogon japonicus</i> (Thunb.) Ker Gawl. – promising lawn-forming plants for the subtropical zone of the Black Sea coast of Russia

Abstract

The lawn coverings creation in the humid subtropics zone of Russia is one of the topical areas of ornamental horticulture. This is due to the high requirements for year-round decorative plantings, the peculiarities of natural and climatic conditions and the general lack of issue knowledge. This direction is of particular importance in plantations located in shaded areas under the canopy of tree crowns, where, in addition to common for the region unfavourable factors of the hydrothermal regime, insufficient illumination is added, which together limits the possibility of traditional cereal grasses cultivating. Evergreen grass-like ground cover plants can be a complete substitute for lawn grasses in shaded areas. The aim of the research was to determine the degree of drought resistance of Liriope graminifolia (L.) Baker and Ophiopogon japonicus (Thunb.) Ker Gawl. and the ability to maintain decorativeness during the period of unfavourable hydrothermal conditions in the summer in the humid subtropics of Russia. The studies were carried out in 2013-2018 on the Black Sea coast of the Caucasus in the Sochi region, in plantations (on test plots with an area of 5-10 m2) and in conditions of vegetation experiments (in containers with a volume of 2 liters) on the territory of the Kuban Subtropical Botanical Garden (settlement Uch-Dere), according to generally accepted methods adapted to the studied taxa. It was found that an important mechanism of adaptation of the studied plants to drought is the ability to accumulate and redistribute moisture between vegetative organs, providing a high water content in the leaves. The decorativeness of O. japonicus and L. graminifolia in open ground in the atmospheric moisture absence lasts up to 12-14 days, in a vegetation experiment (container culture) – up to 14-16 days. O. japonicus and L. graminifolia retained the ability to self-regenerate up to 35-37 days of the experiment, and then the plants died. The consequences of summer drought in the studied plants were compensated by active autumn growth. Unlike classic lawns, which require daily watering, lawns from O. japonicus and L. graminifolia should be irrigated with a long (more than 12-14 days) absence of precipitation in the summer months.