Aquatic Plant Identification

Defining Features for Aquatic Plant Identification

Aquatic plants are identified by examining four useful visual cues: growth form, leaf shape, color, and habitat. Learn to read these characteristics, and aquatic plant identification will no longer be a guessing game.

Growth Form

The growth form describes how the plant behaves in the water. Check it first, as it divides species into clear categories:

• Submerged. It lives entirely underwater, from root to tip. Hornwort and anacharis are clear examples — both grow this way and feed directly from the water column.
• Floating. It floats on the surface, while its roots hang freely below. Duckweed, frogbit, and red root floater grow rapidly in bright light.
• Emergent. The roots are in the substrate, and the stems and foliage rise above the water level. Cattails and pickerelweed grow along the edges of ponds.
• Carpeting. Low-growing species that creep along the bottom on shoots. Monte Carlo and dwarf hairgrass form dense carpets at the front of a planted aquarium.

Growth form alone eliminates half the contenders, so always start the recognition process with it.

Leaf Shape

In order to identify aquarium plants correctly, you should analyze leaf structure. Several different shapes are found in aquariums:

• Strap-like. Long, ribbon-like leaves that sway in the current. Vallisneria is the most obvious example, with leaves that can reach over 60 cm in length.
• Needle-like. Thin, grassy foliage. Dwarf Echinodoria and dwarf Sagittaria look almost identical in stores, which misleads many buyers.
• Broad oval. Broad, rounded leaves on stiff stems. Anubias and most Echinodorus have this shape, and the leaves feel leathery to the touch
• Feathery. Finely dissected foliage that spreads out underwater. Cabomba and Myriophyllum have this foliage to absorb more CO2. 
• Rosette. Leaves radiate from a single central crown rather than climbing the stem. This is how Amazonian swords and crypts grow.

The combination of a leaf shape and growth characteristics usually allows for determining the species ID with the greatest accuracy.

Color

Color narrows the search and is best used in the aquatic plant identifier to distinguish species with similar leaf shapes. Light, CO2, and nutrient levels affect color, so consider it a supporting characteristic:

• Green. The default color for most aquarium species. Java ferns, Anubias, and mosses remain green under almost any conditions.
• Red and pink. Ludwigia, Rotala, and Alternanthera turn red under strong light and in iron-rich water. A pale red color usually indicates a deficiency of one of these elements.
• Brown and bronze. Some Cryptocorynes and buce varieties have these shades naturally. Brown on a normally green plant indicates a problem, not its identity.
• Purple-tinted. Alternanthera reineckii and some Ludwigia strains have purple tints on the undersides of their leaves.

You should consider color as a last criterion and compare it with shape, since the same plant can change several shades depending on the environment.

Habitat and Placement

The location itself is a clue in the process of aquarium plant identification. Pond species, such as water lilies, prefer an open surface, standing water, and sunlight. Aquarium species also follow a logical placement: carpets remain in the front of the tank, stem plants fill the back wall, and rhizomatous species, such as anubias, are attached to rocks or driftwood rather than buried in the substrate. 

Marsh species, such as peace lilies, are often sold as aquarium plants but rot once they are completely submerged. If it dies in your aquarium, the culprit is usually an inappropriate habitat. 

5 Common Aquatic Plant Identification Mistakes

Aquarium plants can sometimes be confusing because leaf shape, growth form, color, and habitat can indicate different species. Below you'll find common mistakes in aquatic plant identification and how to avoid them.

Avoid these five mistakes, and you'll improve your chances for a confident identification.