Phenology is the study of periodic events in the life cycles of organisms and how the timing of these events is influenced by weather and climate. Derived from the Greek word φαίνω (phainō, or “to show or bring to light”), phenology is concerned with the appearance of transient phenomena that we often consider harbingers of the changing seasons. The emergence of flowers, the arrival of migratory birds, the breeding of amphibians, and the metamorphosis of butterflies are all phenological events. Humans have used these events as markers of the natural calendar for millennia, not only to help comprehend Earth’s seasons, but also to aid in the development of agricultural practices. Today, we use phenology as a powerful tool to track the effects of a changing climate on the organisms around us.
With spring around the corner, it’s the perfect moment to witness plants readying themselves for a flurry of activity. We often consider winter a time of dormancy, when the metabolism of many plants grinds to a halt, but most deciduous species have already prepared for the upcoming growing season. In a stunning variety of shapes and sizes, buds are truly the complete package! Contained in these protective structures are the primordia—the earliest differentiated tissues—that will rapidly develop into flowers and foliage with the advent of warmer temperatures and longer days.
A profound lack of snow and unseasonably warm weather this winter provide ideal conditions for observing plant anatomy. Those who stray from the Arboretum’s paths and pull aside branches for close inspection will be rewarded with an array of buds in different colors and forms. Some are warty and organic, such as the white oak (Quercus alba) pictured above. Some are elegant and otherworldly, like the flowering dogwood (Cornus florida). Some, such as the Japanese walnut (Juglans ailantifolia) are downright strange!
Throughout March, changing hormonal signals will cause dormant buds to swell. Eventually, as leaf and flower primordia develop into organs, protective bud scales will open and fall away, revealing the tender new growth of the coming season. The timing of these dynamic events varies between species. Some plants, such as the colorful members of the Hamamelis (witch-hazel) genus, will flower throughout winter, while others, like the fragrant Tilia americana (American basswood), will hold out until late spring.
To learn more about phenology, become a member of the Arboretum’s newest volunteer citizen science group, the Tree Spotters. Through training sessions, lectures, and group events, we monitor 55 trees throughout the Arboretum and collect phenological data for the benefit of scientists, educators, and active citizens. With all this beautiful weather, we’re gearing up to continue our second season with a training session on Saturday, March 12 from 12:30–3:00pm. If you’re interested in citizen science, ecology, climate change, botany, or simply spending more time outdoors, come check us out!
To see more beautiful buds at the Arnold Arboretum, visit my blog.