<p>Herbaria have a rich history dating back to the sixteenth century and have grown over time to house specimens that represent global plant diversity. Although herbaria have been the foundation for research in plant taxonomy and systematics, their use has expanded to include fundamental ecological disciplines, such as species interactions. Plants engage with other organisms in a complex web of interactions, which can be mutually beneficial (such as pollination) or competitive or consumptive (such as herbivory, pathogen attacks or competition with other plants for limited resources). Understanding the long-term trends of these species interactions requires historical data, which might best be obtained from herbarium specimens. Herbarium specimens are increasingly being used to study long-term trends in plant biotic interactions, and new developments in genomic methodologies are further expanding the use of herbarium specimens for studying plant interactions across time and space. These approaches enable targeted sequencing of highly degraded DNA. Climate change might be disrupting these interactions in a way that can lead to loss of beneficial interactions in favour of antagonistic interactions, which can potentially reduce the functioning of biodiversity at regional scales.</p>