Identifying Chara (Muskgrass)
Chara identification is important for two reasons: (1) it must be distinguished from true aquatic plants, particularly from submerged invasive species like hydrilla, and (2) it must be distinguished from Nitella, the closely related charophyte genus with different ecological preferences and management considerations. This guide covers all key features for accurate field identification of chara and differentiation from look-alike organisms.
Key Identification Features
1. The Garlic Odor: The Fastest Test
Pick up a sample of the submerged material and crush a stem or "leaf" segment between your fingers. If you smell garlic or a skunk-like odor, you have Chara. This smell is one of the most reliable quick field tests in aquatic plant identification — it is produced by volatile sulfur compounds unique to the genus Chara and is absent in Nitella and all true aquatic plants. If the material has no odor or smells green/planty but not like garlic, it is either Nitella or a true aquatic plant.
2. Rough, Gritty, Calcium-Encrusted Texture
Feel the stems between your fingers. Chara stems feel distinctly rough or gritty — a tactile quality caused by calcium carbonate (lime) that precipitates onto the surface from hard water. Many chara beds are visibly grayish or whitish due to this calcium encrustation. The rough, gritty texture is in contrast to the smoother feel of most true aquatic plants (though some species like hydrilla also have roughness from leaf serrations). When chara beds dry out, they become crispy and calcium-encrusted — giving them a dusty, pale appearance that is immediately distinctive. This calcium encrustation is most pronounced in hard-water lakes and is absent or minimal in soft-water lakes.
3. Plant-Like Form with Whorled "Leaves"
Chara grows upright from the sediment, with main axes (stems) from which whorls of smaller branches ("leaves" or branchlets) emerge at regular intervals, mimicking the whorled leaf arrangement of true submerged plants like hydrilla and elodea. The overall form closely resembles a small submerged plant 10–50 cm tall. The "leaves" (technically branchlets) are arranged in whorls of 6–12 around the main stem, giving a classic "whorl" appearance similar to true aquatic weeds.
4. No True Roots — Only Rhizoids
Chara attaches to the sediment not through true roots but through rhizoids — colorless, hair-like structures that anchor the organism without the vascular function of true roots. If you gently pull chara from the sediment, you will see these fine, colorless, hair-like rhizoids attached to the base. They do not have the white, structured appearance of true plant roots.
5. Reproductive Structures (When Present)
Chara produces distinctive reproductive structures visible with a 10x hand lens during the growing season (spring through fall). The female structure (oögonium) is a small, somewhat egg-shaped structure surrounded by a spiral of cells. The male structure (antheridium) is a small, round, orange-colored globule. Both are produced at nodes along the branchlets. Oögonia, in particular, look like tiny striped eggs or corn kernels at the "leaf" axils and are unmistakable once recognized. Their presence definitively confirms Chara identification.
Comparison to Nitella
Nitella is closely related to chara and grows in similar habitats. Key distinctions: Nitella lacks the garlic odor (crush a stem — if it has no odor, consider Nitella). Nitella typically has less calcium encrustation and feels somewhat smoother. Nitella tends to be brighter, more translucent green versus the gray-green or whitish of chara in hard water. Nitella prefers slightly softer, more acidic water than chara. See the full chara vs. nitella comparison for additional detail.
Comparison to Hydrilla
Hydrilla and chara are sometimes confused when both grow in similar habitats (shallow, clear water). Both have whorled structures around a central axis. Key distinctions: Chara smells like garlic (hydrilla has no distinctive odor). Chara feels gritty/rough due to calcium encrustation; hydrilla feels smoother, with roughness only along the leaf margins (the serrations). Hydrilla has simple, flat leaf blades; chara has multi-branched branchlets at each node that look like miniature branches, not flat leaves. Hydrilla has tubers at the sediment surface; chara has rhizoids. These distinctions are clear once both organisms have been examined.
References
- Wood, R.D. & Imahori, K. (1965). A Revision of the Characeae. Cramer, Weinheim.
- UF/IFAS Center for Aquatic and Invasive Plants. plants.ifas.ufl.edu/Charophyte