The Eolh-sedge is mostly to be found in a marsh,
it grows in the water and makes a ghastly wound,
covering with blood every warrior who touches it.
Eolh is an Anglo-Saxon word describing a kind of sawgrass that grows in marshes all over Europe (though we have no way of knowing now exactly what species). It has sharp, cutting edges; dangerous for anyone walking through with bare skin. An older Germanic name, Algiz, is linguistically related to the Elk, and so the Elder Futhark rune is often associated with defense. In his book Wyrdworking: the Path of a Saxon Sorcerer, Alaric Albertsson extends this meaning to the Anglo-Saxon elk-sedge, theorizing that the cutting nature of the elk-sedge is protection for the marsh - in contrast to Thorn, a sharp and dangerous plant that is regarded as an ill omen.
The wikipedia article on Agliz, which is actually very informative, talks about the transition from the rune's initial sound as an ending 'z' to its Anglo-Saxon use, a 'x' or 'ks' sound. I feel the Anglo-Saxons saw the marsh as a dangerous, and yet mystical place. To me, this rune represents the dangers and benefits of traveling out into wild places where people are not necessarily welcome. Rather than being protective, I see this as a warning: come no farther, traveler, the dangers of the marsh lie beyond.