isolate clover leaves on grass

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Hello everyone,

I am quite new to imgae processing and am trying to use isolation methods on an image taken of my lawn. I want to isolate the clover leaves on the image as objects. How can this be done? I tried some basic isolation techniques with thresholding, dilation and eroding, watershed etc. but I can not find the right method or the right parameters. The main problem is, that the whole image is somehow all green and the clover is mixed with grass So it is very hard to distinquish between the objects and most importantly isolate single leaves. I think the best way to go is by shape, but I do not know how to do this, yet. Can someone point me in the right direction? You find a sample image attached

Regards SEB