Schoenoplectus californicus
NPPA pest plant
Environmental Weed (2024)
Common names
Californian bulrush
Biostatus
Exotic
Category
Vascular
Structural class
Sedges
Simplified description
Tall (up to 4 m) dense clump forming rush, with no apparent leaves, dark green rounded stems (triangular near the base) and rusty brown scaly flower heads formed near the tip of each stem.
Flower colours
Brown
Detailed description
A tall rhizomatous sedge 1–3–(4.2) m × 10–35 mm, with green to dark green stems triangular near the base, round in upper parts. Leaves are reduced to brown papery basal sheaths. Inflorescence apparently sub-terminal dense; rays 4–10, pendulous, each with 1–5 spikelets on ultimate rays, primary rays usually 3–10 cm long. Spikelets rusty brown, ovoid-ellipsoid to cylindrical, 5–12 × 2.5–3 mm. Nut cream to grey, broadly obovate-elliptic, plano-convex, 2.9 × 1.7 mm.
Similar taxa
The native sedge Schoenoplectus tabernaemontani. Key differences are the round bluish-green stem, smaller size and clustered, not drooping flower heads of this species. Schoenoplectus pungens (Vahl) Palla differs by its consistently triangular (in cross section) culms, and sessile 1–3 spikelets. Overall it is a much smaller plant than either of the other two species.
Distribution
Restricted to Northern Wairoa River, Northland and Waikato River delta where it is abundant. A few other sites resulting from plantings.
Habitat
Coastal river banks and estuaries.
Conservation status
Not applicable
Detailed taxonomy
Family
Ecology
Flowering
November–April
Fruiting
November–April
Year naturalised
1992
Origin
Western North and South America, possibly eastern parts of the Pacific
Reason for introduction
Accidental, likely through contamination of ballast
Tolerances
Prefers brackish water, cold tolerant.
Control techniques
Not usually controlled in New Zealand, but may be controlled manually, mechanically or herbicidally depending on situation.
Life cycle and dispersal
Long-lived perennial. Seed is viable, but seedlings have not been observed in the field. Movement of rhizome fragments by water is likely to be a major dispersal mechanism. Seed is long-lived, the surrounding bristles readily attach themselves to feathers, fur and clothing. This species was distributed in the past as a plant suitable for constructed wetlands to treat farm/domestic effluent.
Other information
National Pest Plant Accord species
This plant is listed in the 2020 National Pest Plant Accord. The National Pest Plant Accord (NPPA) is an agreement to prevent the sale and/or distribution of specified pest plants where either formal or casual horticultural trade is the most significant way of spreading the plant in New Zealand. For up to date information and an electronic copy of the 2020 Pest Plant Accord manual (including plant information and images) visit the MPI website.
Environmental Weed (2024)
This plant is named in a list of 386 environmental weeds in New Zealand 2024 prepared by DOC. 759 candidate species were considered for inclusion on this new comprehensive list of environmental weeds in New Zealand. The species considered were drawn from published lists of weed species, lists of plants that must be reported or managed by law if observed, existing national and regional programmes and agreements for pest management, and species already managed by the Department of Conservation (DOC). Candidate species were then assessed to see if they were fully naturalised and whether they have more than minor impacts in natural ecosystems. Read the full report here.
Referencing and citations
References and further reading
de Lange PJ, Gardner RO, Champion PD, Tanner CC. 1998. Schoenoplectus californicus (Cyperaceae) in New Zealand. New Zealand Journal of Botany 36(3): 319–327. https://doi.org/10.1080/0028825X.1998.9512573.
Attribution
Factsheet prepared by Paul Champion and Deborah Hofstra (NIWA).