Coding phenological growth stages of yellow bells (Tecoma stans (L.) Juss. ex Kunth) based on BBCH scale and its implications for urban greening

The precise knowledge of the seasonal influence on phenology, timing and duration of different growth stages (phenophases) exhibited in a life cycle of a plant is crucial for undertaking several crop management decisions. The reproductive growth stages hold a particular relevance in this regard that conveys a 'seasonal shift' and also a 'shift' in the timing, duration and intensity of vegetative and reproductive growth stages due to subnormal micro-climate induced by climate change. The present study investigates the phenological growth stages of Tecoma stans - a drought tolerant, yellow flowering shrub with a versatile use for urban greening and beautification. Till date, the phenological characteristics in T. stans have never been codified or described so far. The study was undertaken with an objective to codify the seasonal change in the phenological growth stages of T. stans using bi-numeric BBCH (Biologische Bun-desantalt, Bundessortenamt und Chemische Industrie) scale under subtropical climatic conditions of North West India. The experiment was planned on T. stans planted as a shrubbery block in a randomized block design layout. The distinct phenological growth stages of this shrub were represented through photographs. The year-round phenological calendar was also evolved exhibiting the time lapse of different phenophases along with their frequency and intensity of occurrence. Seasonal variation in mean temperature and precipitation markedly affected the phenological behavior of T. stans that exhibited seven major phenological growth stages namely, seed germination, leaf development, elongation of lateral shoots, inflorescence emergence, flower development, pod development and maturity of seed. The investigations undertaken are of vital interest to the urban landscape managers for the selection of species not only based on their aesthetic attributes but also to consider their functionality associated with the site-specific conditions. In addition, the salient findings will help deepen the understanding of weather-induced 'eventful' interactions of pollinators and flowers of T. stans that greatly benefit in a symbiotic manner, ensuring the survival and perpetuation of the species. The newly developed scale provides a unified standard for describing and identifying the phenological growth of T. stans that can potentially be utilized as a reference scale for undertaking future phenological studies.