Watch one tree change its calendar

Choose a tree you pass often and mark four events: first open bud, first full leaf, first ripe fruit or seed, and half the leaves coloured or fallen. Photograph from the same position and keep the date. The discipline is repetition. After a year, you have a small phenology record—a calendar of one organism’s visible seasons.

One tree cannot diagnose climate change. Timing also responds to species, age, shade, rainfall, pruning and a warm wall nearby. Long, standardised records across many sites are needed to separate a trend from noise. Yet the modest practice changes attention: “spring” stops being a date on a calendar and becomes a sequence of local events you can compare honestly.