The recent study by Humphreys et al., reporting extinction of almost 600 plant species globally, represents a groundbreaking effort at compiling direct data on seed plants. We applaud Humphreys et al. for quantifying plant extinctions because they formulate an important and testable hypothesis. However, their study missed many extinctions and rediscoveries of seed plants in the United States and Canada. Our team of experts has been compiling a list of extinct plants of North America north of Mexico. This work is challenging and time-consuming, given the complexities inherent in botanical diversity, the incomplete status of taxonomic understanding, vagaries of reporting, and complexities of phytogeography.