Please refer to this thread for a bit of background: The thread "Maidenhair fern" in Plant Database forum

I am trying to figure out if my fern is Adiantum aleutian or A. pedatum. It seems it would be A. aleutian since A. pedatum does not thrive in the Pacific NW and I've had mine for several years. But I did buy this from a nursery, so it would be either I suppose. In trying to figure out how to differentiate between the two, I find A. aleutian has 'deep sinuses in the black lobes' whereas A. pedatum does not. I don't know what that means. I also find that A. aleutian has 'bifurcating fronds that radiate pinnae on one side only,' which I also do not quite understand. Can any of you fern people give me an easy to understand way to differentiate between western and northern maidenhair fern? Thanks.

My photo is currently under the A. pedatum entry, and if it is incorrect I will propose that it be moved to A. aleutian - just trying to figure out which it is.

I found this under Cultivation details

This species is often divided into three separate species by botanists - the type species is found in eastern N. America, A. aleuticum is found in western N. America and a third species is found in eastern Asia[270].


website: http://pfaf.org/User/Plant.asp...

Not sure if info is exact. This is a tough one Deb!

I read this bit from http://www.greatplantpicks.org...
Geek Notes
Closely related to Adiantum aleuticum is the Northern maidenhair, A. pedatum; in fact, they were once grouped together under one name until botanists separated them. However, the east coast species does not grow well in the Pacific Northwest. The plants gradually lose vigor and fade away.

****How to tell the difference between the two? **** A. aleuticum has deep sinuses in the blade lobes, but A. pedatum does not. (Sinus depth.How the far the leaf goes into toward the vein.)

So finally, I googled Adiantum aleuticum frond in images in a tab of its own, and looked closely at the frond and did the same with pedatum, clicking between the two tabs, and there is a difference, but slight. Hope this helps. Pasting in all the photos required downloads, which is stupidly involved in a chromebook laptop, I apologize for the work required.

The lengths to id are amazing sometimes. Not even sure this will pin it down completely for you.

i have quite a few of them growing wild in No Calif amongst the Redwoods
just did some searching and it looks like we might need to clean up our listings
looking at images on line i can not tell the difference between them
Adiantum pedatum
Cal Flora - http://www.calflora.org/cgi-bi...
USDA - https://plants.usda.gov/core/p...
Flora of No America - http://www.efloras.org/object_...
Wildflower Center - https://www.wildflower.org/pla...
Adiantum aleuticum
Cal Flora - http://www.calflora.org/cgi-bi...
USDA - https://plants.usda.gov/core/p...
Flora of No America - http://www.efloras.org/object_...
Wildflower Center - does not acknowledge it
what do we do now ?
do i ask for my image to be moved ?