Verdure is a term that describes green, flourishing vegetation, particularly grass. This term is used in the Spanish title of When We Cease to Understand the World, Un Verdor Terrible, which roughly translates to “A Dreadful Verdure.” Verdure is one of the central motifs of the text.

Its meaning is revealed in the letter Fritz Haber writes to his wife at the end of Chapter 1. Haber has developed a fertilizer that will stave off famines and prompt population growth. However, he worries that:

[T]he world’s future belonged not to mankind but to plants, as all that was needed was a drop in population to pre-modern levels for just a few decades to allow them to grow without limit, taking advantage of the excess nutrients humanity had bestowed upon them to spread out across the earth and cover it completely, suffocating all forms of life beneath a terrible verdure (33).

While nitrogen fertilizer may seem like an unambiguously beneficial scientific discovery, the “terrible verdure” is emblematic of the way that even seemingly neutral or positive scientific innovations fundamentally change the world and may have unintended, negative consequences. This motif reappears in Chapter 5 in a passage that expresses concern about a “vegetable plague” and in the night gardener’s reflections on plant life and its relationship to death.