T6 wetlands are dominated by Lyngbye's sedge (Carex lyngbyei).  They are found in the upper sedge marsh zone in the upper reaches of estuaries.  Monotypic stands are common.

T6 corresponds with Vince and Snow's (1984) 'Inner Sedge Marsh Zone 7', estimated to be inundated on only the highest spring tides, or an average of 2 times per summer on the Susitna Flats (with a range of 0-5 times per summer), in upper Cook Inlet, Alaska.  Vince and Snow found that water was retained for greater than 5 days per inundation. 

Just below T6, pools containing the Alaska Natural Heritage Program tracked rare plant (S2S3) Kamchatka spikerush (Eleocharis kamchatica), along with common mare's tail (Hippuris vulgairs), and saltmarsh starwort (Stellaria humifusa) are frequently encountered. These pools often lie between T6 and a Ramensk's sedge (Carex ramenskii) zone (T5).  Landward, T6 typically borders a beachrye (T7) or mixed forb / grass component (T8).

T6 is typically composed of tall, dense sedges over a thick organic soil, often the hydric, Clunie histosol.  Occasionally Lyngbye's sedge is found growing inland, in small dense stands far removed from tidal influence.