Herbaria

Herbaria are collections of plant and fungal specimens. A collection of fungi is sometimes distinguished as a fungarium. In the case of plant pathogens, these specimens are usually pressed and dried, and stored in paper packets. Sometimes they are mounted on paper.

Herbarium specimens provide a record that a particular taxon was found in a specific place, at a specific time. If taxonomy changes, the specimens can be redetermined and we will still know what they were — compare this to a written record, which only tells us what the recorder thought something was at the time. The following is an example of a specimen mounted on paper, but there is a major problem. Can you see what is wrong?

There is no date or location beyond “England”, and there is no other information! This specimen could be the only record of the species from a certain site, but we will never know. It is very important to label your specimens. The one thing we can do is determine and redetermine the identity of the specimen — the post-it note shows my determination of the specimen as Microbotryum flosculorum (de Candolle) Vánky, 1998, and if this species is ever split up or merged with another species, future researchers will be able to redetermine it.

Information with a specimen or record

You must include the following with any herbarium specimen or iNaturalist record:

Location

At the very least GPS coördinates or a grid reference, often with a placename too. You can be vague if you want but I like to be accurate enough that if someone wanted to refind the host plant they would have a decent chance.

Date

This is useful for understanding when pathogens appear and how this is changing with climate change.

Host plant

This one is really important! If you are only taking a single leaf, other people will not be able to identify the host plant. Many old records are less valuable because the host plant has not been included, as old species have been split into many different host-specific species, and without knowing the host plant we do not know which of the new species the record refers to.

An alternative if you aren't sure what the host plant is, is to make a separate collection of the host plant itself and make sure the records are linked in some way. You can also simply include enough of the host plant that ID is possible from your specimen, as in my Entyloma specimen shown above.

Collector

The name of the collector, i.e. your name!

You should aim to include the following with your specimens and records:

Taxon name

You might be surprised that this isn't essential, but you can donate indeterminate specimens (“indets”) to a herbarium. They can always be determined later, and if you think it is an interesting specimen that is worth keeping then there is not reason not to just because you don't know what it is.

It's also worth noting that you don't have to identify something to species, you can leave it as a higher taxon such as Entyloma or even a very broad group like Pucciniales (Rust Fungi). Any level is useful information.

Habitat notes

These can be useful for researchers studying the ecology of pathogens.

Collector number

Most collectors have a continuous series of numbers that uniquely identify every specimen they have ever collected. For example, the first specimen I ever collected is JD1, the thirty-seventh is JD37, etc.

Determiner

If someone else identified the specimen for you, write their name. If someone else helped you to identify the specimen, write your name and their name, etc.

iNaturalist record number

This means the specimen can be linked to your iNaturalist record, with associated photographs. This is the number at the end of the URL, eg for the packet shown above the URL is https://www.­inaturalist­.org/­observ­ations/­228476520, so the number is 228476520.

Other notes

For example, is this the first record from the area? Is the taxonomy controversial?

Keeping a personal herbarium

It is very easy to start and maintain a personal collection of specimens. I use brown paper bags, which you can buy in bulk cheaply online. They are quite rough and ready but they work, and are easy to take into the field.

I dry specimens by placing them between a few sheets of toilet paper, then sandwiching them between books. Sometimes I have to swap the paper several times before they are dry.

Ideally you should store your specimens in a cool, dry place such as a cardboard box. There are lots of pests to watch out for! I find Psocids (booklice) sometimes like to nibble at my specimens... Freezing affected specimens can save them, but household freezers may not be cold enough. This is one reason why important specimens should be given to research herbaria, which use integrated pest management and generally put specimens into deep freeze for several weeks before they enter the main collection, to avoid bringing in any pests.

Donating to research herbaria

Important (and unimportant!) specimens should be donated to research herbaria, where they will be kept and maintained indefinitely. If a taxon is new to an area, or may be a new species altogether, you should make sure to donate a specimen. If you want to keep your own, you can just make duplicates of a specimen — this is also a good idea if you want to donate to a local herbarium and a large one like Kew.

To donate, you should get in touch with the herbarium curator, generally by email. Note that a few larger institutions (notably Kew) have different curators for the herbarium sensu stricto (i.e. just plants) and the fungarium.

I have made a very non-exhaustive list of things to look out for and collect for research herbaria here.