What to photo -- Carex sedges
Identifying Carex on iNaturalist is really hard. Why? First, Carex are diverse (about 2000 species worldwide, close to 500 in North America north of Mexico), and these simple plants have fewer traits than most. Second (partly a result of the first), differences between species are often subtle and often involve a combination of multiple traits. Third, the photos on iNaturalist often don't show the needed traits. You can do something about that third one.
The list below explains the most important traits to photo for Carex identification. Of course, even perfect photo sets may languish unidentified for a while, because Carex identification knowledge is mostly local (another result of that diversity) so even Carex "experts" don't know many of them.
What if you don't photo all these things? Sometimes you don't need to. Sometimes one or two photos are enough. Trouble is, if you don't know what species you're dealing with, you probably don't know which traits you need.
- Habitat. Most Carex are microhabitat specialists, so this can be an important clue. You can just make notes, rather than photo, but was it growing in water? In a bog? Lake margin? In upland forest? Prairie? Roadside salted in winter? On serpentine or pumice or other unusual soils?
- General appearance. Is the plant cespitose (growing in one clump) or rhizomatous (spreading by rhizomes)? Is the inflorescence nodding or erect? Is it obviously green or blue-green? If the photos don't show these traits well, try to get enough information to remind you, and write about it.
- Inflorescence. Are the spikes crowded or separate? Is the lowest inflorescence bract longer or shorter than the whole inflorescence? In some cases (especially if the individual spikes are short) it's important to know if the staminate flowers were at the base or top of the spike, so include a close photo.
- Perigynia. Unless the spikes reveal most of the length of the perigynia ( +/- = utricles, fruits), break up a spike and spread the perigynia on your hand (or any other convenient surface) and photo them. Try to show both sides. Get close enough to see the hairs, if the surface is hairy. While you're doing it, include some of the scales (bracts) that grow between the perigynia.
- Leaf sheath front. As in grasses, the sedge leaf consists of a blade (usually flat, the part we think of as a leaf) and a sheath (which wraps around the stem). Where's the front? The blade attaches to the back of the sheath -- think of Superman's cape attaching to his shirt. The front of the sheath is the other side, where the big S is on Superman's shirt. The front is usually hyaline (transparent when fresh, whitish when dry). In a few species, it may be green and veined like the back. The front may be brownish or coppery. It may have tiny red dots. The top of the sheath (at the level where the blade attaches) may be flat across or concave, but in a few species it extends upwards like a sheath. In a few species the top is thickened. The sheath may be "cross rugulose," with horizontal waves or corrugations. In many species, the leaf sheath decays leaving a network of fibers.
- Plant bases. Some Carex are green all the way down, but in some the lower parts of the leaf sheaths are conspicuously reddish, brown, or black.
(6.5) In certain Carex of eastern North America, the leaf sheath back is also important. Not so much in the Pacific Northwest.
(6.6) The ligule is important in some species, though I don't use it in the ones I know. To photo, pull the leaf blade a little away from the culm (stem) and photo the triangular area where the blade is held tight to the culm by a little membrane.
