Pecan trees are notorious for alternate bearing. Some varieties are prone to bigger yields one year and smaller crops the next, while others tend to produce good crops every year. A pecan tree has both male flowers (pendant catkins), and female flowers (erect spikes), on the same tree. Type I (protandrous) pecans have male flowers that release their pollen before their female flowers are receptive to pollen shed. Type II (protogynous) pecans release their pollen after their female flowers were receptive. There is also variation in flowering time among varieties within each type. Both types must be present to get pollination and subsequent nut development, and the bloom periods must overlap. Experience has shown that three or more pecan varieties planted together provide the best pollination, and therefore the biggest nut crops. Plants respond to environmental changes by shifting the timing of life-cycle events. Phenology is the simplest process to track the ecological changes of species in response to climate change. In fact, a species, phenology scale includes understanding the influence of seasonal and year-toyear variation in climate on the species’ life-cycle events and activities. Understanding the phenology is essential to provid a standard format for recording plant responses to climate change, plan for how these changes affect activities such as resource management and production practices, and help in decision-making and adaptation in response to variables, changing climates and environments. There are two major approaches to monitoring and recording phenology: phenophase status and phenological event monitoring. Field observations of individual plants using the two approaches yield different types and amounts of phenology data. Phenophase is an observable stage in the plant’s annual life cycle that can be defined by a start and endpoint, and generally has a duration of a few days or weeks. The phenophases are used as a standard unit of observation, and maintain uniformity and simplicity within phenophase definitions to facilitate comparisons across taxa. A phenological event is a point in the annual life cycle of a plant, generally marking the start or endpoint of a phenophase, and can be recorded as a calendar date. In this approach, the observer watches for a defined phenological event during the plant’s life cycle. The observation of the life cycle event using the phenological event approach results in one data record compared to the multiple data records for the same event observed with the phenophase status monitoring approach. Application of decimal codes for pecan growth stages, including timing and external morphology, provides a useful guide for pecan growers. It can help growers manage different practices such as pruning, thinning, and applying pesticides in their orchards. As phenology scale can be used to define the start and end of the growing season, it can also be used in global climate change research, considering the great diffusion of pecan growing areas around the world.