Does anyone else have any unusual or odd examples of how they identify taxons in the field?
For example:
A standard way to identify Cucurbita foetidissima (Buffalo Gourd) is to key it out.
Another way is to shake the vine a bit and if it suddenly smells like a mixture of pungent cheese and foul body odor, that’s a fairly reliable diagnostic.
Share your examples, please!
I suppose odor can be a legitimate “field mark” for identifying many plants, even though we humans don’t typically utilize it as much as other animal groups! Two examples come to mind:
(1) Long ago in my college days in California, I was shown that you could distinguish the otherwise very similar Ponderosa Pine and Jeffrey Pine because, if you stick your nose into the crevices of the bark of each, one smells like vanilla ice cream and the other does not. (I can’t recall which was which.)
(2) Several species of the attractive “false pennyroyal” genus Hedeoma here in Texas have different odors. When the leaves are crushed, one smells like lemons, another like peppermint, and another reportedly like some other aromatic–I’ve forgotten the details and I get them mixed up in any event!
Eastern spadefoot toads (Scaphiopus holbrookii) smell vaguely of peanuts.
Eastern hellbender (Cryptobranchus alleganiensis) eggslime tastes very bitter.
Ponderosa pine has a faint vanilla smell but my sense of smell probably isn’t good enough to rely on that. I’ve never sniffed a Jeffrey Pine.
Buffalo Gourd definitely has a funky odor that you can often smell before you see the plant.
I could usually tell I had a House Mouse rather than a native mouse species in one of my rodent live-traps even before opening it, based on the distinctive musky smell of that species.
For most shelter-building caterpillars, you mainly identify them based on what they build and the plant they build it on, because the actual caterpillars are very similar-looking (and frequently concealed and/or tiny). Unfortunately, because there usually aren’t great descriptions of the shelters, many of these species are only represented by adults on iNat. But here’s one example: pine tube moth
Sometimes I will identify a plant by the insect feeding on it, instead of the other way around, since I often know the insects better! Especially in the case of galls - if I see a blueberry stem gall, or a witch hazel cone gall, I immediately know what plant I’m looking at 
Hey welcome bugbear!
I don’t have too much to comment, but over here snails in the genus Oxychilus should be handled and their bodies poked to find out if there’s a garlic butter smell for positive ID…
Unless I am just that gullible.
I was shown a different way: touch the cone with the palm of your hand. If you feel the sharp points, it’s a “Prickly Ponderosa”; if you don’t feel anything sharp, it’s a “Gentle Jeffrey.”
Friendly fir, spikey spruce
California Torrey vs Douglas Fir or other conifers - I tell people the easiest way to check is the grab a branch, and if your hand starts bleeding, it’s a torreya.
Stinging phacelia and stinging lupine are likewise pretty easy to identify :)
The slap test-- Ulmus rubra vs. other elms. Pick off a leaf, slap it hard between your hands, and if its little hairs stick it to your hand like velcro, you have “slippery elm.”
I don’t think of scent as odd, since fynbos has many fragrant plants.
Buchus and pelargoniums have provided essential oils for commercial culinary use for a long long time!
But an odd example. Bend the leaf, if you get a waxy white line it is
https://www.inaturalist.org/taxa/593894-Searsia-lucida
hence the deliberate taxon photo.
Even when it’s a snail?
(I guess may just be me then…)
Oxychilus
Another set of ID methods that I as a birder use (and I’m certainly not alone in this) is habitat and general “gestalt”. Or to be more specific, microhabitat and flight behavior. One of the best examples I can think of is Winter Wren. Here in Texas in the winter, if I’m around a lot of downed dry/bare brush in tangles low to the ground, maybe with a fallen tree trunk or two, maybe on a slope adjacent to a waterway, and I see just a glimpse of something tiny and dark–not even sure if its a bird, insect, mammal, or anything–my mind automatically begins to think “'Winter Wren”. I might not actually detect a shape, a feather, or anything; the ID just comes from microhabitat and motion of an object.
Agreed. Gestalt is hard to define but includes all those variables such as location, habitat, microhabitat, the size and shape of the organism, its movement and posture, and other characteristics that are often subtle but in combination add up to an ID.
There are quite a lot of strange ID methods for fungi: taste, smell, color change with damage, appearance of liquid exuded with damage, color change with application chemical reagents, glow in the dark or fluoresce under UV light. And I guess less weird methods: change in appearance over time, appearance of spore print, appearance of spores under microscope, habitat, and associated species (food or mycorrhizal partners).
Here are a couple I learned today on a meeting of the Botanical Society of Britain & Ireland.
The yellow waxcap fungus Hygrocybe glutinipes is usually recognised by being viscid (slippery) but it loses the sliminess in dry weather when it looks very like H. chlorophana. A dry glutinipes will stick to your wet lip because the slime gets rehydrated. H. chlorophana won’t stick to your lip.
The similar rushes Juncus effusus and J. conglomeratus can be separated by waving them briskly, as you would wave a fan. J. conglomeratus will buckle and effusus won’t because the latter has denser pith.
A mixture of pungent cheese and foul body outdoor? My wife would certainly argue that, for her at least, there is NO difference. [sigh]
Have not done it myself but have heard from multiple people at meetings!