Image comparisons can be one of the quick and dirty ways to determine a plant identification. Images published in floras, monographs, and scientific journals have varying degrees of use. A good picture, taken in the field and properly identified cannot be underestimated in its utility. Often these images at least help you get to family or genus. The idea of, “it looks a lot like this,” can actually help significantly narrow the list of possibilities. Let’s be honest, even established experts in plant identification have been known to flip through a book and see if the images help. The problem exists in the details. Often species are differentiated based on cryptic characters that cannot be verified in an image. This can mislead the identifier into thinking “Eureka, I’ve found it!” when in fact you have missed out on some key defining characters. This has somewhat been alleviated by high resolution imaging of verified herbarium specimens, however, resolution is still limiting, and the inability to dissect an image can be a problem.
Images can come in many forms: pictures in a field guide, scientific drawings of precise scale and detail, and online images – both professional and unverified. Images of herbarium specimens are even available now! While online images are becoming widely available and field guides can be locality specific and very helpful – the user is still limited by the sampling and can often only find images for a subset of possibilities. In addition, images may lack the detail to differentiate close congeners (members of the same genus). Also, online resources are not always verified, and web pages are not static, making them potentially unreliable sources.
Any match using an image should be verified with technical description, herbarium specimens, digital keys, and/or expert determination.