Ginny B's picture

Lichen questions

Being very new to the subject, I am wondering if the different species of lichen grow and fruit at different times of the year just as fungi do? Does a lichen change its colour and/or shape) greatly as it grows?

I have tried hard to identify what I might be looking at by comparing my photos with those I can find on line or in books and there seems to be great variability between illustrations of lichens under the same name.



synan's picture

A short answer

A full answer could fill several chapters of a book! I am no expert, but the in the absence of greater wisdom...

Lichens don't have the seasonal restrictions of many plants and non-lichenised fungi, and can persist for many years - thousands in the case of some crustose species. I have always assumed they grow more quickly and fruit more easily in the summer months, and this seems generally to be the case, but this paper demonstrates the variation in the months of peak growth for Rhizocarpon geographicum.

I am struggling to think of examples where colour might evolve with age, except in diseased thalli, but colour can vary widely with habitat and rain - eg the common Xanthoria parietina, which is usually seen yellow, can be grey in the shade and green when soaking wet. Some species have colour morphs where the photobiont differs (eg see here) or the chemistry differs (as here).

Lichens do evolve in appearance as they grow, often developing reproductive structures (eg apothecia, soredia and isidia) that aid identification. For this reason, young material isn't always identifiable. Not all species can be identified from a photograph anyway; some require chemical testing and/or microscopy. As you have discovered, many lichens are extremely variable and have lookalikes to be considered. Learning the diagnostic characters makes it easier to name the less typical examples, and when comparing photographs, it's best to look at a wide range. With perseverance, some of the more common species become a bit easier. I have found that making mistakes is a great way to learn!


Ginny B's picture

Thank you so very much for

Thank you so very much for your not so short and very interesting answer to my questions.

I have to admit that at times I wonder why I ever started trying to learn about lichens! They seem so hard to distinguish one from another. I’ve sometimes thought that it would be helpful to look them up by colour, but from reading that link you showed me I realise that even that wouldn’t work!

It doesn’t help that my photography leaves much to be desired. Only today I saw on the rocks a lovely specimen of a fruticose lichen of a type I’d not come across there before and tried to get a good photograph, but when I got home and put it on the computer everyone of that particular lichen was out of focus. :( Oh well, I can go back and try again another day.

In spite of such frustrations, I find learning about lichens fascinating and am enjoying the process.

Thank you again for your help.


synan's picture


I don't want to undersell colour. It usually is a reliable indicator, except in wet specimens, but the general form and structure is the first thing to consider. The British Lichens site is worth trying if you know the growth form but not the genus. Using your fruticose example, you could look under the category of 'Shrubby lichens' to see if any of the thumbnail images look close, then under 'Species Gallery' for further photos. Some of the other categories are subdivided by colour - proof that colour is very useful.

To reinforce my point about wet specimens, look under 'Leafy and squamulose lichens', then click on the last thumbnail under 'Squamulose lichens' to encounter some wet Romjularia lurida. This is what it looks like dry.

Of course, there are other excellent websites and I am not showing favouritism here!

Oh, and I struggle to photograph fruticose species too.


Ginny B's picture

Great tips. Thanks.

Those are really helpful tips, so thanks again.

I've just got back from trying to find the same fruticose lichen to photograph again - and failed to find it. I rather think that the stronger north wind today has dried it out even though it rained last night and it now looks like all the others on that rock. A pity because it was the first time I had been able to see soredia really clearly. But I'll keep looking as it is where I pass by pretty regularly whilst walking the dog.

Squamulose lichens is a term I'm unfamiliar with having so far on the course only learnt of crustose, foliose and fruticose; but looking at the photo of dry Romjularia lurida I think I may have seen something very similar in growth pattern. I certainly wouldn't have recognised the two photos you indicated as being the same organism!

As to helpful websites, for me they all have something to offer and I am grateful for the time and effort involved in the first place in creating such sites and for the excellent photos and descriptions that help towards identifying the different species.