A herbarium is a scientific repository or collection of dry or botanized plants generally referred to as superior or flower plants (angiosperms and gymnosperms). It also comprises the group of ferns and related ones (pteridophytes), as well as moss (musci) and fungus or mushrooms, including algae (except microscopic organisms, which as collections are deposited with another system. Associated to herbariums, it is common to have collections of seeds, fruits, wood, photographs of plants, and other things related to plants, including botanical gardens. It is also a priority to have a specialized library to identify plant material.

The goal of a herbarium is to have a systemized representation of plant biodiversity to study their presence with precision in a specific geographic area in time and space. Taking this into account, studies in flora allow us to know the composition of plant communities better, besides having first-hand information for land studies in ecology, evolution, territorial regulation, and environmental impact. It is also essential to establish protection measurements to specific taxa through their entry to NOM-059 ECOL [Mexican regulations] and international agencies such as IUCN-CITES “red book”.

Herbariums as ours have emerged from the need of knowing plant composition of a specific area or a plant group of a geographic area.  With achievements, perseverance, and support, herbariums grow and expand their local, state, regional, national and continental, including worldwide coverage. We hope that as our herbarium reaches maturity, it covers the Mexican northwest, still fragmentarily known.

At present, it is necessary to have a collection permit issued by INE-SEMARNAT [National Institute of Ecology, Ministry of Natural Resources] to carry out floral studies.  The permit includes obligations to environmental authorities, such as reports on the specimens collected, respecting a volume of collection, and restricting disruption of protected species. It is essential for the collector to have a notebook to register individual collections with geographic and other types of notes (use, phenology, etc.) same which are included in the database.

Identification of specimens is performed by the herbarium staff that uses some floral work for the area as a main instrument. The analysis of the specimen implies anatomical and morphological knowledge of the different plant organs. Sometimes it is required to consult a specialist in the reference group, with whom shipments need to be performed, either in or out of the country.

Botanized specimens (dehydrated, pressed, and identified) are mounted with glue in a 42 x 48 cm card. Each one has a tag with taxonomical, ecologic, and geographic data. Our herbarium is up to date in capturing this information in a data base in Excel for quick reference on this and other aspects that are added. It is good to mention that the specimen mounted should adequately represent the plant collected. If it is smaller than the card, the specimen will be mounted complete; if it is a specimen like a tree, the sample should be a branch with leaves and reproductive structures (flowers, fruits, seeds); sometimes this last one goes with a photo of the complete specimen showing its growth and any other details.

Many herbariums, as ours, also have sample exchange agreements with other institutions. This favors each collection notably. In particular, in the last years, there have been important exchanges with the Museum of Natural History of San Diego (SD) and the University of Arizona (UA).   One of the important points of herbariums is to publish and show their results in different forums and at different levels, as well as attending loan and information applications.

Herbariums, as other collections of organisms, play an important role as reference points in a world that is rapidly losing wild spaces and their biodiversity content, the reason why they are becoming more important each day as reference points.