Conservation Status:  Safe for Now

Land & AquaticSpiny Rush

Juncus acutus leopoldii Plants & Trees

Aquarium of the Pacific - Online Learning Center - Species Print Sheet

Spiny Rush
© Michael Charter. Used with permission.
Spiny Rush
© Michael Charter. Used with permission.

Species Overview

Spiny rush’s other common names are Leopold’s rush, wire grass, and southwestern spiny rush. It is an erect, very spiny plant that is able to live in both freshwater and saline environments. It was introduced into southern Australia where it is considered to be a weed due to its success as a primary colonizer. Grazing animals avoid grazing where this plant thrives. Once it becomes established, it covers the area and out-competes almost all other vegetation.

Species In-Depth | Print full entry

At the Aquarium

Cuttings and seedlings for our Shorebird Sanctuary were donated by Stewards of the Los Cerritos Wetlands located in Long Beach, California.

Geographic Distribution

California’s central & south coast, southern Channel Islands, Sonora Desert, Baja California, Arizona, South America, South Australia, & South Africa. Native to the Mediterranean region, western Europe, North America, & Africa.

Habitat

These plants can tolerate both fresh and saltwater habitats. They are found in coastal salt marshes and disturbed saline areas as well as in alkaline, wet places in the interior along wetlands or pond. They are known to invade lowland grassland and grassy woodland, riparian vegetation, and areas of low fertility.

Physical Characteristics

The cylindrical stems are numerous, erect, smooth, dark-green and pithy, tapering to a sharp point and bearing stalked flower clusters. The leaves are similar to the stems but they lack flower heads and their tips end in a very sharp spine. Although new leaves and stems continually replace old ones, most new growth occurs during the spring.

Spiny rush does not flower until it is at least two years old. The flowers occur near the tops of the stems and are small, green to brown in color. The fruits are 5-6 mm (0.2-0.3 in) long and appear as reddish brown, nut-like clusters that consist of 3-celled capsules. The clusters are somewhat rounded and about 30 mm (1.2 in) in diameter. There are very small oval seeds in each capsule. The root system consists of a fibrous mat and short rhizomes.

Size

Spiny rush grows to approximately 0.5-2 m (1.6-6.6 ft) in height with a spread of 1-2 m (3.3-6.6 ft).

Diet and Feeding

Spiny rush obtains its nutrient through photosynthesis.

Reproduction

Although spiny rush can grow from pieces of old crown, seeds are the vectors by which these plants spread. Water is the major dispersal agent for the seeds that can germinate at almost any time of year. Seeds are also carried to areas where spiny rush is not native in hay and mud attached to vehicles and livestock.

Adaptation

The limited surface area that the narrow leaves of these plants have helps them to retain moisture, especially important to the plants that grow in the desert.

Conservation

The California Native Plant Society lists spiny rush as rare in California. Plants disturbed by the construction at the Bolsa Chica Ecological Reserve in Southern California, were saved and then replanted as part of the restoration of these wetlands.

In contrast to California, in southern Australia where Juncus acutus was introduced, spiny rush is listed as a noxious weed. Control varies by state and territory and includes both regulations that prohibit planting and some that require landowners to eradicate the plants

Amazing Facts

Spiny rush can grow to form impenetrable boundaries that keep livestock and humans away from water. When the plants grow in drains, they can obstruct water flow resulting in flooding.