Plant Species of San Jacinto Mountain: Pictorial Identification Guide to High-Elevation Sedge (Carex) Species

Carex senta
swamp sedge
Our most common meadow sedge

Table of Contents

Pictorial Identification Guide
    Carex fracta
    Carex senta, C. heteroneura, C. nebrascensis
Key To Identify Carex Species
    Introduction to the Key
    Key With Pictures
    Key Without Pictures

Carex fracta
fragile sheath sedge
Our most common and widespread sedge


Sedges, grasses and rushes are difficult for most people to distinguish, since they don't have what we think of as normal flowers with showy petals. Even many botanists have trouble distinguishing species of these plants, since it usually involves microscopic examination of small parts for subtle differences (example). Even the famous botanist Harvey Monroe Hall punted on doing the identifications of grasses in his 1902 Flora of the Pine Belt of San Jacinto Mountain, saying:

For the determination of the plants of this difficult order the author is under obligations to Mr. Joseph Burtt Davy, of the University of California.
and for the sedges:
For the determination of this and the following species of Carex the author is indebted to Professor C.F. Wheeler, of the Michigan Agricultural College.

For the sedges, Hall couldn't find an expert in California at that time!

Hall of course did excellent field work in finding and discriminating the grass and sedge species at San Jacinto Mountain. The above comments just mean that he sent out his specimens to experts in those fields to attach a name to each of the species he recognized as being distinct in the field.

To put this in perspective, after doing the first flora of the higher-elevation San Jacinto Mountain for his master's thesis back in 1902, for his doctoral thesis Hall monographed all the Asteraceae of southern California, often called the darn composites since so many of them look similar! Lyman Benson, who worked on difficult plant groups such as cacti, dedicated his book Plant Taxonomy to Hall, saying:

Hall ... introduced a new era in taxonomy of plants. ... his monographic studies of genera so difficult that others avoided them - Atriplex, Potentilla, Artemisia, Chrysothamnus, Haplopappus and various genera in the .. Madieae.

(Taxonomy is the practice and science of classification, in this case separating plant species and subspecies. Each distinct entity is called a taxon; the plural is taxa.)

You are clearly in good company if you are unsure about how to identify sedge species.

The situation hasn't changed much today. Often professional botanists will do most of any identification they need to do themselves, but take the grasses, sedges and rushes into a herbarium to get them identified by experts in those areas. To a good first approximation, the only people who can really identify many of those species are people who have two important characteristics. First, they have a lot of experience with those species. Second, they work in a herbarium that has good examples of all the species, whose determinations have been confirmed by experts in each species, that can be used for comparison.

Fortunately, plant taxonomy becomes a lot simpler if you restrict yourself to a small area. We have only eight sedge species at high elevations at San Jacinto Mountain, and most of them, including the two most common species, can immediately be identified at a glance in the field, or from a photograph. This webpage shows you how to do that.

A higher-level webpage to come in the future will discuss how to tell sedges, grasses and rushes apart. Until I add that page, perhaps this standard mnemonic, and this link, will help:

Sedges have edges, and rushes are round, and grasses have nodes from their tips to the ground.

If in doubt about whether you have a sedge after using that mnemonic, it might help to know that the word Carex comes from the Latin word for cutter, from the sharp leaf and stem edges. You can very carefully run your finger along the edge of the leaves, and you will get instant feedback on whether you have a cutter or not. Try not to end up getting cut by Carex!

Specifically, the species included here are the higher-elevation sedge (Carex) species of San Jacinto Mountain. The area considered here is Tahquitz Valley and above, which includes Tamarack, Round, and Long Valleys. The lowest elevation of this area is 6600 feet (2000 m) at Caramba. For completeness, the key includes a few species found on the nearby west side of San Jacinto Mountain at elevations above 6600 feet that so far have not been found at Tahquitz Valley and above.

This paper is in three parts. The first part is on this webpage, and is aimed at most people, and mainly provides an identification through matching photographs. The second part is aimed at people who want to learn in more detail how to identify the sedges here, using an illustrated key to come up with a determination. The third part is the traditional non-illustrated key, which is easier to carry around and use in the field once you know how to work it. The second and third parts are each on separate webpages.

Pictorial Identification Guide

First, a note on names. Common names are rarely used for sedges; most are just made-up names that are translations of the scientific names, as is obvious from the table below for six of the eight species. Most sedge species simply don't have vernacular names that are commonly used. If you are going to learn sedges, and have to learn their names anyway, you are much better off just learning and using their scientific names. Nearly all the names are easy to pronounce from the spelling, and most are only two to three syllables.

We have only eight Carex species in this higher-elevation area. Their names and relative abundance from an extensive survey of Willow and Tahquitz Creeks are given in the next table:

Scientific NameCommon Name#SurveysSum #PlantsSum #Areas
Carex abruptaabrupt-beak sedge813524
Carex fractafragile sheath sedge151073118
Carex heteroneuravari-nerved sedge2554
Carex hoodiiHood's sedge455
Carex mariposanaMariposa sedge1102
Carex nebrascensisNebraska sedge000
Carex rossiiRoss' sedge121
Carex sentaswamp sedge151485117

There were a total of 15 separate surveys done. The column #Surveys gives how many surveys in which each species was found. In each survey, we estimated the minimum number of plants for each species, with a maximum value of 99 plants. The column Sum #Plants is just the arithmetic sum of the estimates from each survey. In each survey, we also estimated the minimum number of areas in which each species, with a maximum value of 9 areas. The column Sum #Areas is the arithmetic sum of the estimates from each survey.

We also have estimates of the abundance of each species from the other surveys that Dave Stith and I have done, including all the trails, ridge tops and meadows. In those surveys, Carex fracta is the most abundant by far, since it can grow outside of creek areas, but C. senta can not. Carex nebrascensis was found in a few of those surveys, but not in the Creek surveys themselves. Hence it is listed with zero abundance in the table above from those surveys.

There are only two Carex species that are widespread and very common in Tahquitz Valley and higher elevation: Carex fracta and Carex senta. The table above shows this clearly; they are the only species to be found in every one of the 15 creek surveys. These two species are also far and away the most abundant in the other surveys Dave Stith and I have done.

Hence if you just learn those two species, you will be able to identify literally 99% of all the Carex plants in the highest-elevation part of San Jacinto Mountain. (Remember that those are minimum abundances in the table above. In particular, Carex senta got the highest minimum abundance estimate on every survey (15*99 = 1485). C. fracta got the highest minimum abundance on most of the surveys, too.)

By great good fortune, it is a piece of cake to discriminate these two species at a glance or in a photograph; their inflorescences look completely different (don't go by the color, which changes with time):

Carex senta
Its inflorescence consists of just 3-4 very noticeably-separate spikes, that are quite long relative to their width.

Carex fracta
Its inflorescence consists of 7-35 spikes, some of which are not clearly separate, that are not much longer then wide.

Other characteristics of these two species are discussed below.

We are lucky here to be able to discriminate our two most common species so easily; believe me, it didn't have to work out that way! In fact, it does not work out that way in most other areas of California.

Carex fracta

Carex fracta is the most widespread species in this area. Dave Stith and I have found this on 30 different surveys at San Jacinto Mountain, in nearly every area that has even a bit of moisture. This species has the lowest water requirement of the species that grow in moist areas, so it grows in even the uppermost part of many drainages, sometimes without any other wet-loving species growing with it.

Hence if you find a sedge in this area, if you simply guess that it is Carex fracta, you are going to be right the vast majority of the time (the only exception is if you are in a wet meadow, where you should guess Carex senta; see below).

The flowering stems of Carex fracta are typically 2-3 feet (0.5-1.2 dm) tall, and are held well above the leaves. However, plants vary considerably depending on how favorable their environment is. Some plants have flowering stems only a few inches (~10 cm) tall, with just a single stem or two; some plants are large clumps of 30-40 stems, each three feet (1 m) tall, as shown in the next two pictures:

A small quite-unhappy Carex fracta plant on a hillside near the Jolly Spring Drainage on the Devils Slide Trail

A large Carex fracta plant, consisting of many three foot (1 m) tall stems connected by rhizomes, in upper Tahquitz Creek. A different sedge, Carex heteroneura, is partially seen at lower right. Note its much more compact and different-colored inflorescence. Just below middle of the photograph there is a dark-brown inflorescence of C. heteroneura seen directly in front of a straw-colored inflorescence of C. fracta.

However, no matter the size of the plant, the flowering stem of any Carex fracta that you find will look similar to one of the versions in the following pictures:

Inflorescences with the female flower in bloom, with the styles showing. The inflorescence on the left also has a few male flowers in bloom, with a few anthers showing.

Inflorescence with a few anthers showing.

Inflorescence with mature fruit

The spike at top left has dropped about half of the mature fruit, leaving the series of depressions visible where the fruit used to be attached (the white arrow points to this part). The straw-colored part above it is from the spike bract, and is not connected to the stalk with the series of depressions (the two upper red lines point out that bract; another red line shows another such bract). The black arrows point to several fruit that have fallen from this inflorescence.

To be confident that you are seeing this species, all you need to note is that the inflorescence (the part containing the flowers shown above) is 3.5-5 x longer than wide, 1-3 inches (2.5-8 cm) long, with 7-35 individual spikes. If it satisfies all of those characteristics, and you are in the area defined above, it is C. fracta.

If you are someplace else, like in the city of Idyllwild, Garner Valley, the Sierra Nevada or Minnesota, these characteristics may not be enough to uniquely identify this species. That's why Carex identification gets complicated, since so many species from different areas look alike.

As you might expect from the variability in the number of individual spikes, an inflorescence with only seven spikes on a one foot tall plant is going to look quite a bit different from an inflorescence with 35 spikes on a three foot tall plant. As a result, you might think those two versions are a different species, but they are not, as long as they have the characteristics given above. If strikingly-different appearances were the criteria for defining species, we'd have to separate humans into a large number of separate species.

In addition, the inflorescence looks quite different when it is in flower, with stamens sticking out; when the stamens are lost but the spike is still green; when the seeds are ripe; and when the spikes turn brown and start to lose their flowers. The pictures above show some of this variation, as well as variation in the leaf-like bract underneath the inflorescence.

That specimen with a very long bract fooled me into thinking it was a different species that I had been looking for. But when I examined it carefully at home, it was still Carex fracta and not the other species I was hoping it would be. (I vouchered that specimen if you want to examine it yourself. It probably produced its long bracts since it was growing inside another plant, and was starved for light.)

Carex senta, C. heteroneura, and C. nebrascensis

Carex senta is the next most widespread species in this area. This is the most abundant species in the wetter meadows, and is equal in abundance to C. fracta in creeks with flowing water most of the year. It is present in 29 of the surveys I've done, only one fewer than the 30 of C. fracta. Hence if you find a sedge in a wet meadow, if you simply guess that it is Carex senta, you are going to be right the vast majority of the time.

If you are in a creek with flowing water most of the year, don't guess; just take a look at the inflorescence to discriminate these two species.

Carex senta is even more recognizable at a glance than C. fracta, since its inflorescence consists of just 3-4 very noticeably-separate spikes. The top spike usually appears as a slightly-different color than the lower spikes since it consists of male flowers, and the other spikes consist of female flowers:

The inflorescence of Carex senta in full fruit.

When I was a beginning botanist, I absolutely loved sedges with an inflorescence like this, since they were just about the only sedge I could hope to recognize by sight.

While the inflorescences of Carex senta pretty much always look the same, the overall size and robustness of the plant is extremely variable. In creeks, it usually appears similar in habit to Carex fracta, producing fairly well-defined smallish clumps. However, in meadows, or any other place where it can grow undisturbed for a long time, it goes crazy, and produces massive clumps that merge to form a sea of leaves:

Carex senta in the bottom of Skunk Cabbage Meadow on 21 October 2009. The picture shows a patch about six feet by six feet (2 m x 2 m) in size. Individual plants are about 2-3 feet (~1 m) in diameter, and you can only approximately tell where the raised clumps are.

The Jepson Manual says:

Forming large, dense, raised clumps connected by rhizomes, in ± continuous stands or not.

Walking across a meadow composed of old Carex senta plants is indeed a hazardous undertaking to your ankles since calling the clumps raised is a severe understatement. The clumps are often several feet off the ground, and it is difficult to know where exactly the clump is, since the leaves cover the whole area. Imagine trying to walk blindfolded through a football field covered with a thousand football players crouched in the take cover position, with about the same space between the football players as each player takes up, and you'll have some idea of what it is like to walk through these clumps.

A small part of that size variation is shown in the following photographs, from specimens growing along within just ~30 feet (10 m) of each other in lower Willow Creek:

A continuous stand of Carex senta growing along lower Willow Creek. The plants in the upper picture are either younger, or don't have access to as much moisture, as the plant in the lower picture. The plants in the upper picture are on the top of an incised bank, significantly above the water table. The plant in the lower picture has its roots in the water visible in the Creek right next to it on the right of the photograph. The legs of Dave Stith are at upper right in the lower photograph; he is standing about a factor of two farther from the camera than the Carex senta.

There are two much less abundant species here that are similar to C. senta, and might be confused with it, C. heteroneura and C. nebrascensis

Text unfinished at this point

Other species yet to be added

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Copyright © 2009 by Tom Chester.
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Comments and feedback: Tom Chester
Updated 9 November 2009.