Seed productivity of northern white cedar (Тhuја оссidentalis L.) cultivars in South Karelia

Northern white cedar (Тhuја оссidentalis L.) is a North American coniferous plant widely used in landscaping. In the Botanic Garden of Petrozavodsk State University, a collection of 45 cultivars of northern white cedar has been collected, and systematic observations on the plant growth are being made. The seed productivity of 14 cultivars aged 14-20 years was studied using an original technique that allows calculating the number of cones and seeds per 1 m² of a tree crown and in general on one tree. In 2019, the number of cones per 1 m² of crown for different cultivars varied widely - from 1116 (Aurea Group) to 3672 ('Spiralis') with an average of 2158. Accordingly, seed productivity also varied within 5578-18359 seeds per 1 m² crown. Seed productivity of one plant varied from 31,300 to 338,713 pcs. seeds and was determined by the size of the plants. Seed germination was 50–60 %, which is comparable with similar indicators in different parts of cultural area. Seeds from northern white cedar cultivars in the Botanic Garden of PetrSU are used to obtain planting material of seed origin and selection, for the exchange of seeds with botanical and forestry organizations.