Dreaded Ovales

“The Dreaded Ovales” article was printed in Harbinger Fall 2014, Vol. 31 No. 3 which is a publication of Illinois Native Plant Society. The dreaded Ovales are difficult to identify sedges.

Read other articles on Carex on the Illinois Native Plant Society www.ill-inps.org

Carex Corner: The Dreaded Ovales

The Ovales (oh-VAHL-lees) are in the genus Carex and have wand-like heads of small spikes or spikelets in rows or clusters. Their identification creates more angst than any other group of Carex. One of the problems is some species have a different form of seed head after the first culms mature with a switcher-roo to a different shape later in the summer. The Flora of North America Volume 23: Cyperaceae: reveals “Those late-season forms are not accounted for in the key or descriptions, and plants collected late in the season lacking intact spring inflorescences may be impossible to key. “

Notice “may be” which gives some lee-way to those smart enough to mark a plant in the field and then return to it a month or two later. Or, a botanist like myself that relies on growing Carex in pots on the patio so I can watch the changes for my “ah-hah!” moments.

The Ovales can make you crazy. Many people give up or leave it to the experts known as Caricologists. The late Jim Zimmerman of UW-Madison wrote in Fassette’s Spring Flora of Wisconsin p 34, “ The perigynia and spikelets change rapidly after flowering, causing the same species at 2 stages of development to look less alike than 2 different species at the same stage”.

The petaless flowers of Carex have perigynia, sac-like envelopes, each with a single seed-like achene. Groups of sacs form spikes or small spikelets at the seed head. Most seed heads are simple but some are compound with side branches. The Ovales are distinguished by flat sacs with tissue-thin wings that usually reach from the tip of the beak to the base of the sac. A few species like C. cristatella, have narrowed wings that end partway down the sac. Magnification is necessary.

Sometimes the achene inside the sac makes a conspicuous bump that is overlain with support lines known as nerves. The number and width of the nerves can be quite diagnostic for identification, and like forensic botany, gives a usable fingerprint pattern.

While many Carex species can be identified by their sac “fingerprint”, the Ovales are tricky beasts that vary in having raised nerves on both sides of the flat sacs, or one side only or none at all, some referred to as obscurely nerved. (an arg moment). The point is the descriptions of Carex species give ranges of variable traits and the Ovales are the winners in the “stump the botanists” category. The terms “sometimes, often, and usually” apply to traits of the Ovales.

Dr. Mohlenbrock mentions in Flora of Illinois: Sedges: Carex that C. molesta is one of the most common sedges in Illinois. Yet ask any roomful of botanists if anyone has seen one lately, you could expect a lot of blank stares. It is one of the easier ones to spot since its seed heads overtop their clump of grass-like leaves with a wiry culm tipped with usually three ball-shaped spikes. If there were more Ovales with orbicular spikes like C. molesta, instead of the more common oval spikes, the group might have been named Orbales. (groan)

Puzzlers are those with distinct seed head shape which have the sacs that may or may not match the images in manuals. Botanists must consult several manuals and websites, and they do not always agree. Do we really expect the keys in a manual for Michigan plants to be similar to one for Illinois? Populations vary by locations.

The keys in lab manuals assume you are in a lab and can magnify the sacs to see the details, after all most are about size of a sesame seed and are measured in millimeters. Some keys, such as the one on p 339 in Flora of North America: Volume 23 require a microscope that can magnify 30–40 times, and that’s medium to high power on a dissecting scope. A hand lens will not do the job.

Why the need for such detail? Some species have tiny bumps called papillae on the leaves, yet some variable species such as C. festucacea may or may not be papillose. Minute traits are helpful, yet there are other ways to distinguish the species. The best leads in the key are the numbered list of choices that lead to the correct species.

The range of sac sizes reveals different positions in the spikes in the seed head but the sacs grow larger as they mature, and the species do not mature at the same time. Some continue to increase size well into summer, so a June specimen could be misleading and appear different in August. Dry sacs develop better fingerprint-like lines or ridges called nerves when the tissue between the support nerves wilts, so they appear raised.

The growing achene in the sac also becomes more pronounced in shape outline. (I forsee in the future forensic botanists will use a perigynia scanner like an optic nerve scanner that will determine species). The sac length in millimeters is not enough of a clue and the sac width often determines the species, along with nerves present. C. brevior is nerveless on its inner face while similar C. molesta is faintly nerved.

The one millimeter difference between C. festucacea and C. brevior’s sac length is diagnostic. C. festucacea sacs are less than 4 mm long, while C. brevior’s are 4 mm or longer. (Squinting exercises the eye muscles and may be good for you). Guess where most of the sacs will measure of the species you collect? That’s why botanists meticulously pick apart the spikes of Carex. If a sac falls easily off the spike, consider it too good to be true. It’s likely a dud and does not fit the sac shape or size given keys.

L–R: Carex molesta with clustered seed head L–R: Ovate perigynium of C. molesta and and C. brevior with spaced overlapping C. brevior, broadly ovate.

Other clues are whether the sacs are widest at the middle, below, or above the middle. C. brevior, C. festucaea and C. molesta sacs are widest below the middle, most of the time. Others have sacs less than 2 mm wide, and for C. festucaea, that’s most of the time. That means it will key under two key leads: either “sacs greater than 2 mm wide” and again in “sacs less than 2 mm wide”. “Clear and discernable traits” does not apply to many Carex unless key-makers “bridge the gaps” and include highly variable species in more than one key.

But that’s why people who solve Sudoku Rubik’s cubes naturally migrate to identifying Carex. It’s the challenge and like other games, each section of Carex has their own level of identification difficulty. I do not recommend Ovales for beginners.

Linda Curtis’s humorous pseudonym Lindaeus, offers empathy for Linnaeus
who first grouped the new worlds Carices. Lindaeus says,

“The range of two similar species sac sizes will be the overlap size on any species you try to identify in the field.”

Linda Curtis is author of Woodland Carex of the Upper Midwest. www.curtistothethird.com

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