Hiding Among Us: Identifying a Non-Native Rush

By John Krapek

Hiding Among Us is a WRA blog series in which we focus on the trickier side of botany – namely, identifying weedy plants that could have unfortunate implications for habitat restoration and, often, on meeting regulatory agency performance criteria for restoration sites and other projects with re-vegetation components.  In this post, we focus on a newcomer: Australian rush (Juncus usitatus).

A Basic Description

Australian rush is an introduced, non-native grass-like species (graminoid) that has been increasingly observed in the wild in northern California and has also been appearing in nursery stock around the Bay Area in recent years.  Because it appears superficially similar to our common native soft rush (J. effusus) and spreading rush (J. patens), Australian rush has been mistaken for these two species and has been propagated and used for restoration as a “native” species.  However, Australian rush does not have the same ecological qualities as our native species and therefore is not appropriate for restoration or planting in the wild.

Some Key Identification Characteristics

Although many of the morphological characteristics that distinguish Australian rush from its two native relatives require magnification, one characteristic can be seen with the naked eye.  Australian rush generally has a “chambered” or “interrupted” pith (spongy vascular material in the center of the stem), whereas soft rush and spreading rush have “solid” or “uninterrupted” pith (see photos to right).

Quickly…

For quick and easy identification, slice the stem open longitudinally and examine the pith.  If the pith is chambered or interrupted, the plant is most likely the non-native Australian rush.  It is important to check multiple stems given that this feature can be ambiguous or, in some cases, not apparent at all.  If the pith is solid and uninterrupted, the plant is most likely one of the native, common rush species.  This is a good diagnostic feature for use in the field; however, if planning to collect propagules of soft rush or spreading rush for use in restoration, the species should be examined closely and verified using an appropriate flora such as the Jepson Manual.

For more Detail…

If you have a microscope or a hand lens available, look at the flowers and fruits.  Australian rush has blunt-tipped flower petals, as opposed to acuminate (sharply tapering) petals in the two native species.  Australian rush also typically has fruits which are larger than the flower petals (extend beyond the petals), whereas the fruits of soft rush and spreading rush are typically contained within the petals.

Questions?

If you have a Juncus specimen which you are unsure of, check with your local herbarium or send a pressed specimen to WRA for identification by one of our skilled botanists.