Northwest Lichenologists

Freezing lichen specimens

  • 26 Nov 2022 9:31 AM
    Message # 13003431

    Hi all,

    I am relatively new to collecting lichens.  I have been told by a few folks that I should place my lichen specimens in a household freezer for between 48 hours and a week. The usual explanation is to prevent degradation of the specimen by either microinvertebrates or "other".  On the other hand, some textbooks and field guides I possess notably do NOT mention freezing lichen specimens anywhere in their introductory chapters.  

    Should I be freezing my dried lichen specimens and, if so, how quickly after collection and for how long?  Is there any evidence that not freezing them is detrimental?  



  • 26 Nov 2022 5:59 PM
    Reply # 13003613 on 13003431

    I recently found an insect (a helpful expert on iNaturalist suggested it may be a nymph member of Psocodea) eating an Evernia prunastri specimen I was looking at under a microscope. So they definitely can be a problem! I immediately put the thallus in my freezer for a week and didn't see them afterwards. I've read alternating freezer and room temperature can be even more effective as well.

    That said, I'm new to collecting too-- I'd love to hear from others who have more experience.

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  • 28 Nov 2022 10:14 AM
    Reply # 13005495 on 13003431

    I don't freeze mine. I don't find things eating my specimens when they are collected in the PNW. Most lichens contain lichen acids that dissuade any grazing! But I definitely have had problems in specimens from California containing something that ate a lot of lichens, especially Melanelia and similar genera.

    On the whole, I'd say it isn't necessary to freeze.

    In the OSU Herbarium, we haven't had problems with lichens being eaten, but we have to be super careful not to bring in insects that might eat the vascular plant collections. So it is protocol to freeze anything coming in to the herbarium.

  • 02 Jan 2023 9:34 AM
    Reply # 13041679 on 13003431

    For home lichen collections I agree with Daphne. I have not seen lichen herbarium collections deteriorate from grazing insects. But if you are affiliated with an institutional herbarium, you should ask the collections manager or director about their policy for freezing botanical specimens. At the University of Washington, where I house my lichens, I have to freeze them for 48 hours, regardless of what I think about freezing.

    At the University of Bergen, in Norway, Tor Tonsberg freezes all lichen collections for a week, before storing in their herbarium. It is all a matter of where your collections are and the policies of the institution of where your lichens are stored.  If storing at your personal considerations home, you get to decide.

    I have seen silverfish in the UW herbarium eating labels. They like the glue that was used on older packets. 


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