Fragile Science


Wood Anatomy Lab at Harvard University Herbarium
Botanical specimens are inherently fragile; they are composed of living matter doomed to wilt, dry, and crumble to dust. The specimens sent to herbaria are housed there to be preserved, their lives suspended indefinitely in time. Many precautions are taken to ensure the longest life span and the best conditions possible for each incoming specimen. But despite the care and devotion from the curators of the herbaria, there are destructive elements waiting around each bend.




Specimens come to the Harvard University Herbaria from across the world. Shipments may arrive from as far as Australia, China, Russia, or as close as areas in neighboring Massachusetts towns. They arrive in boxes dotted with bird droppings, the specimens within wrapped in newspaper or stored temporarily within commercial containers and bags. The packaging from the field is sometimes nearly as interesting as the specimens themselves, as some come in exotic bags and wrappings.

Specimen newly arrived to the Harvard Univeristy Herbarium


These materials were housed in older cabinets, which have become warped over years of temperature and humidity fluctuations, allowing soot and dust to contaminate the items within.


Temperature and humidity control in herbaria are vital to the survival of the specimens. High temperature and high humidity will invite mold to germinate, insects to swarm and thrive, and specimens to age more quickly. Low humidity will dry paper and specimens, making them brittle. Fluctuations in temperature and humidity cause further damage to the specimens. The comfort level for humans and that of botanical specimens differ, and finding a reasonable compromise is difficult. Low temperatures are better for specimens, yet when curators work in the same environment, the environment must meet their needs as well.



The most common insects in the Harvard University Herbaria are silverfish, cockroaches, and beetles, primarily the Herbarium Beetle. Curator Genevieve Lewis-Gentry says that she often sees silverfish scuttling over her keyboard and swarming in spaces within the herbaria. Cockroaches, most commonly the American, German and Oriental, can be seen creeping along the shadows and edges of walls in the basement. Beetle damage is recognized by the small holes they leave as they eat through paper and specimens. Beetle larvae cause much damage as they eat their way to adulthood, crawling and munching through materials. When freezing specimens, temperatures must be low enough to kill not only the adult insects, but also their eggs. Low temperatures, low humidity, and a clean, secure building are the best prevention for insects.

Oriental Cockroach donated by the Harvard Entomology Department
American Cockroach donated by the Harvard Entomology Department

Cigarette Beetle donated by the Harvard Entomology Department


Pest Control


Specimen and paper burned by fumigant.
Throughout the years there have been changes in technologies used to control insects and pests in herbaria. Fumigants were used in the past to protect specimens from insects. Many of these fumigants are now banned from use because they are known to be carcinogenic or otherwise harmful to people and the environment. One such fumigant formerly used by the Harvard University Herbaria was methyl bromide, which is now known to cause ozone depletion and is banned by the Montreal Protocol. Not only are many of the formerly used fumigants harmful to the people who used them, but over time the chemicals have burned through both paper and specimens. Another poison that was regularly used was arsenic, which was sprinkled on specimens to help kill insects and pests. While arsenic is no longer actively used, specimens that were treated with it remain in herbaria today.




The cabinets in which the specimens are housed have changed over the years. Older cabinets, made of wood or metal, were not airtight and allowed insects to enter, as well as light, temperature, and humidity to damage the specimens. More modern cabinets are airtight and better protect specimens against harmful particles in the air, as well as fluctuating temperature and humidity.

Cabinets from 1915 in the Harvard University Herbarium.

Cabinets in the Harvard University Herbarium today.



This acidic paper label has become brittle, discolored and has broken over the years.


Labels are nearly as important as the specimen itself. A label tells where the specimen has come from, who collected it, the plant's features and habitat, the date, the scientific and vernacular name of the plant with variations over the years, and other supplementary information. We know today that the paper used in making labels should be acid-free to prevent degradation over the years, but in the past labels were made without this in mind. Many of the labels in herbaria are becoming brittle; their glued backings are crumbling, their text is fading, the paper is becoming discolored and cracking... too many are coming loose from the specimen and becoming lost amongst the shelves. With the loss of these labels often the identity and provenance of a specimen is gone. Without their identifiers, they are simply objects with no names.

The label on this fossil has become difficult to read.

Chemical Reactions

Other dangers lurk sometimes unrealized by curators. This specimen, which had been housed in the Harvard University Herbarium wood anatomy lab, has an unknown chemical reaction growing upon it which resembles mold.

Chemical reaction resembling mold.




Part of a spirit collection within the Harvard University Herbarium.
The housings we keep specimens in also hold hidden dangers. Spirit collections are those housed within a preserving liquid. These can be dangerous because chemicals can be flammable and toxic. The liquid must be changed relatively frequently; at the Harvard University Herbaria all of the liquid in over 3,000 jars have been changed three times over the past twenty years. A glass jar with liquid inside could crack, and the liquid preserving the specimen could leak. Without its liquid, the specimen will become dry and disfigured. The labels, made of tape and glue will become brittle as they age, and will not adhere to specimens, paper or jars. Acidic paper will become dried and discolored over time, and will not preserve specimens as well as those within non-acidic paper.



For all the care and devotion of their curators, botanical specimens have inherent flaws that play against them. They are susceptible to heat, cold, humidity, mold and insects, as well as to chemicals once thought to protect them. Despite our efforts to prolong their lives, our methods cannot always have a happy ending. And yet, to step away from science and to observe these specimens from a different perspective, the flaws can be touchingly beautiful. The narrow winding holes made by beetles, the fading and distortion of color, the mystery when identity and provenance are swept away by time and dust can capture the mind of an explorer and create intrigue in the hidden dark corners of herbaria. We cannot suspend forever the lives of specimens, but we can respect and appreciate the delicate fragility of science.

Images above are specimens within the Harvard University Herbarium




Bridson, Diane. The herbarium handbook. Royal Botanic Gardens, Kew, 1998.

Conservation Online. Environmental Monitoring and Control, Stanford University. Click here for Conservation Online

Copeland, Marion. Cockroach. London: Reaktion, 2003.

Patkus, Beth Lindblom. "Integrated Pest Management." Preservation Leaflets. North Andover, Mass.: Northeast Document Conservation Center, 2007. Click here for NEDCC Leaflet