Phenological phases of <i>Weigela×wagneri</i> L. H. Bailey under conditions of humid subtropics in Russia

Weigela varieties of hybrid origin, known as Weigela hortensis (W. hortensis C.A. Mey) or <i>Weigela×wagneri</i> (W.wagneri L. H. Bailey) are cultivated on the Black Sea coast of Krasnodar Krai. A current range of this beautifully flowering shrub includes more than 150 varieties. However, only 24 grow in the region and are predominately selected in the early XX century and are rarely used in the landscaping of the resort town. Ornamental varieties of Weigela grow mostly in limited use areas (Sochi Arboretum, Subtropical Botanical Garden in Kuban region, Friendship Tree Garden Museum). The study aims at investigating the phenological phases of <i>Weigela×wagneri</i> L. H. Bailey under humid subtropical conditions of the Black Sea coast, Krasnodar Krai, to be used for the design of gardens with continuous flowering plants, as well as for breeding. The study was conducted in the period from 2013 to 2019 in the Friendship Tree Garden Museum and Subtropical Botanical Garden in Kuban region. The study involved 15 varieties of W.×wagneri. The authors established differences in phenological phases, including the start/end of growing season and flowering, duration of these periods, as well as the sums of effective temperatures required for these phases. The start of the growing season was established to vary from February 12 (Arlequin) with an accumulated sum of effective temperature of 261.2℃ to March 14 (Brictol Ruby) and a sum of temperature of 376.9℃. Differences between varieties in this phenophase account for 30 days. On the basis of the long-term average annual data, the varieties were divided into groups according to the floral initiation: early flowering (from April 14 to April 21) group included Arlequin, Gustave Malet, Mon Blanc, Newport Red, Venusta, Madame Lemoine; medium-flowering (April 22 to April 30) group included Lacepede, Ballet, Pavillon Blanc, Brictol Ruby, Madame Lemoine; Eva Ratke, Kosteriana variegata, Red Prince, Augusta were included into a late-flowering (from May 01 to May 06) group. According to the dates of the start and end of growing season, the varieties were divided into the following phenological groups: EE – Early starting (before Feb 12) and Early ending vegetation (before Dec 05); EL – Early starting (before Feb 12) and Late ending (after Dec 19); LE – Late starting (after March 4) and Early ending (before Dec 5); LL – Late starting (after March 4) and Late ending vegetation (after Dec 19).