Sunbathers vs. the Large-headed Sedge

Some weeks ago there was a letter in a local paper complaining about the “invasion” of Large-headed Sedge (Carex macrocephala) at Air Force Beach in Comox. The complaint was based on the fact that the sedge was taking over the prime sunbathing area and should therefore be removed. Jocie and I decided that it was worth taking a drive out to the beach to assess the extent of this unwanted encroachment.

Large-headed Sedge | Carex macrocephala "invading" the sun bathing area.
Large-headed Sedge | Carex macrocephala "infiltrating" the sunbathing area.

We were pleasantly surprised to find a large and healthy population of Large-headed Sedge in the sandy area between the storm line of driftwood and the base of the hill below the parking lot. The letter writer was indeed correct – the sedge seemed to be doing very well and was entrenched in a significant portion of the bathing area above the high tide line.

Large-headed Sedge | Carex macrocephala showing the spiky head from which it get's its name and that is such a concern for sun bathers.
Large-headed Sedge | Carex macrocephala showing the spiky head from which it gets its name. The sharp edged leaves and this seed head are a serious concern for sunbathers.

Large-headed Sedge, like the name suggests, has a very large spiky seed head that is very distinctive. Sedges resemble grasses but a close examination of their stems reveals some key differences. “Sedges have edges” goes the old saying – rolling a potential sedge stem between the fingers reveals that it is triangular in cross section and solid (not hollow). In contrast, “rushes are round” and pithy inside and “grasses are hollow” and round in cross section.

Large-headed Sedge | Carex macrocephala moderating erosion of the sand at Air Force Beach
Large-headed Sedge | Carex macrocephala moderating erosion of the sand at Air Force Beach

Large-headed Sedge is actually a beneficial plant to have growing in a sandy seashore or coastal dune ecosystem. Its presence moderates erosion by forming long lines of plants that serve to hold the sand in place. The sedge spreads by horizontally spreading rhizomes that are buried in the sand. In a more dynamic dune ecosystem like the dunes in Pacific Rim National Park Reserve (see photo below) the Large-headed Sedge plays a vital role in reducing wind and storm erosion.

Large-headed Sedge | Carex macrocephala at Pacific Rim National Park Reserve working hard to protect the dunes from erosion.
Large-headed Sedge | Carex macrocephala at Pacific Rim National Park Reserve working hard to protect the dunes from erosion.

Taking in the magnificent array of sedges at Air Force Beach I can only hope that these beautiful sedges will emerge victorious in this conflict between nature and sunbathers. Ironically, I wonder what would happen if the Large-headed Sedge was removed? Would the sand eventually vanish with them? In a perfect world, these questions won’t have to be answered.

For more delightful botanical related reading consider Berry Go Round, this month hosted by Seeds Aside.

Berry Go Round

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