How can I properly extract the features of a ferning pattern using image processing?

Using feature extraction, what can I do to distinguish the ferning pattern in a positive fern test? Attached is a sample image from https://commons.wikimedia.org/wiki/File:Positive_Fern_Test_.jpg.

[cr]

You mean to say you want to detect whether or not there is a fern pattern? Do you have images without the fern? Also depends on what other patterns are there that shouldn't result in positive? Training a neural network might be easier.