[Picture of <em>Carex brevior age sequence (Mississippi) Reznicek</em>]

[Picture of <em>Carex specifica Lassen NP 79 (10) PZ</em>]

Late Season Shoots Affect Carex Identification (November 30, 2009)

On any one Carex plant, most of the flowering shoots develop at one time. In many species, those shoots originate in the fall but remain short and undifferentiated until spring. After this first cohort of flowering shoots, additional flowering shoots may develop. These are the "late season shoots."

Why do Carex make late shoots? Two possibilities are that the site experienced a late influx of water, permitting more growth, or that herbivores ate the first cohort of shoots and the plant sent up these late ones.

Late season shoots differ from the main cohort in several ways. Their inflorescences are usually longer than the early shoots and the spikes more separated. However, species that normally have elongated inflorescences, like C. scoparia, may produce compact late season inflorescences. On species that normally have short lowest inflorescence bracts, the bracts of late season shoots are frequently elongated and sometimes leaflike. Pistillate scales tend to be unusually long, sometimes becoming acuminate or even short-awned. Occasionally, they hide the perigynia in species that normally do not have perigynia hidden by the scales. Perigynia on late season shoots may be longer and wider than those of early shoots, with wider wings and lower length/width ratios.

Late season shoots can obscure a sedge's identity, particularly in the section Ovales where species distinctions are subtle to begin with. For example, elongated inflorescence bracts are typical of C. athrostachya and C. unilateralis. Late season shoots of nearly every Ovales can be keyed to one of these two species, if they have elongated inflorescence bracts. Late season shoots with elongated inflorescences can make C. subbracteata key to C. gracilior, or C. abrupta key to C. mariposana or C. specifica. Late season variation in perigynium shape can send species skittering through identification keys in unpredictable ways. We suspect that at least one west coast species (C. ampletens) was named based on late season shoots of something else (C. fracta).

Just about any species of Carex can produce morphologically unusual late season shoots. They seem especially common in the Ovales and other members of subgenus Vignea. We have also seen them on carex hoodii and C. arcta. A plant of C. aurea had a couple of late shoots about 6 cm long with the perigynia separated by about twice their length. Species of section Acrocystis, including C. rossii and C. brevicaulis, may produce late shoots with elongated inflorescence bracts. Some late shoots of the well named Carex brevicaulis (Short-stem Sedge) had inflorescence bracts longer than the flowering culm.

About the only way to avoid being confused by late season shoots is to recognize them and avoid using them when keying a specimen. Track fertile culms back to their roots (necessary anyway in order to collect roots, fruits, and shoots!) and look at their full range of variation. Collect the older shoots, or a combination of older and younger shoots. Of course, if the older shoots were eaten and the later ones grew up subsequently, you may be fooled. Pay attention to the late shoots you see. Some of them have a "look" that you'll come to recognize as meaning they came up late.

Sedges - diverse, confusing, but always fun.

Photos: Age series of Six shoots of Carex brevior (left two are normal) by Anton A. Reznicek. Two shoots of Carex specifica (left is normal) by Peter F. Zika.