It naturally occurs in Australia, New Zealand, Hawaii and South America.

[3] Recently, J. planifolius has been introduced to the northern hemisphere.

[5] It is now well established on Pacific coast of North America, where the plant was first collected in Oregon in 1980.

Juncus planifolius may have arrived as a contaminant in vines planted in commercial cranberry bogs, but is now spreading in native coastal bogs, where it may displace native plants.

In North America, it is recognized by its unbranched stems, basal leaves with no sharp demarcation of sheath and blade, and blackish tepals.