Sid Thomas was an invited speaker at Treeworks Seminar 21 Transformational Nature, held at Kew Gardens, 17 May 2016. Here’s a summary of his two lectures.

Trees are at one end of a spectrum of plant life histories running from extreme perennials to ephemeral annuals. In these two lectures I examine the evolutionary relationship between annuality and perenniality and its implications for the form and longevity of trees. I consider how the durations of individual cells and organs are integrated into the lifespan of the whole plant. The discussion will also compare and contrast the woody plant life form with that of colonial organisms and will consider the role of meiotic and mitotic cell division in rebooting juvenility. By 370 million years before the present, the primeval forest was the dominant terrestrial biome. And then, 70 million years ago, a new group of plants, the grasses, appeared on the scene and set about challenging the dominance of trees by exploiting fire, a devastating new weapon in the evolutionary arms-race. We may now consider it enlightened and civilized to value and even venerate trees; but mankind’s age-old relationship with the forest has overwhelmingly taken the form of slash and burn. These lectures look at cultural responses to the history of the three-way interdependence of people, trees and grasses and the role that lifespans play in this relationship.