Quick Facts

Quick facts

• Wild Rice (Zizania sp.) is an annual or perennial aquatic grass.
• Only one species of Wild Rice, Z. palustris, occurs in Australia, in cultivation in New South Wales.
• Wild Rice (Zizania spp.) is a declared weed in Tasmania. It is not naturalised in Tasmania at present but assessment has shown the weed potential of Manchurian Wild Rice (Z. latifolia) and its annual relatives.
• Manchurian Wild Rice (Z. latifolia) occurs in New Zealand and is a serious weed of freshwater aquatic ecosystems. It blocks waterways, impedes drainage, takes over native aquatic flora and invades pastures.
• Infestation may be controlled with manually or with herbicides.

What Does It Look Like?

What is it?

Wild Rice (Zizania spp.) is an annual or perennial aquatic grass rooted in the substrate, some species with rhizomes or stolons (spreading lateral stems), and with separate male and female flowers on each plant. Stems are upright growing to 5 m high and either emergent or floating. Leaves may be concentrated on the lower portion of the stem or evenly distributed. Leaf sheaths (lower parts of the leaf that envelop the stem) are open, and ligules (the structures between the leaf sheath and the blade) are membranous, or thin and dry, and hairless. Leaf blades are flat, aerial or floating, rough or smooth growing to 1.5 m long (Terrell 2007). Flower heads are branched, up to 120 cm long and occur at the end of stems. Branches are usually unisexual, lower branches with stalked male flowers, upper branches with stalked female flowers and middle branches sometimes with both male and female flowers. Flowers are white to purple to brown. Seed is cylindrical to 30 mm long (Terrell 2007). Species include the annual plants, Southern Wild Rice (Zizania aquatica) and Northern Wild Rice (Z. palustris) and perennials, Texas Wild Rice (Z. texana), and Manchurian Wild Rice (Z. latifolia), known also as Asian Wild Rice and Water Bamboo (Clayton et al. 2006).

Manchurian Wild Rice occurs as a weed in New Zealand and is described as a dense, mat-forming perennial to 2–3 m with rhizomes (spreading lateral underground stems) up to 5 m long and fibrous roots. Harsh, papery, dull grey-green leaves (2–3 cm wide) which are straight, up to 2.5 m long, have a stout midrib, taper to a point, and rustle loudly in the wind. From November to December a purplish or red-brown flowerhead (40–60 cm long) is produced with large numbers of seeds in some seasons (Weedbusters New Zealand 2004; Auckland Regional Council 2007).

For further information and assistance with identification of Wild Rice, contact the herbarium in your state or territory. 

Flower colour

White, Purple, Brown

Growth form (weed type/habit)

Grass, Aquatic

Where it currently grows? Preferred habitat

In its native range, Manchurian Wild Rice (Z. latifolia) grows in the shallow waters of lakes and swamps, forming large patches (Terrell 2007). In New Zealand, Manchurian Wild Rice occurs in fresh or moderately saline water bodies and margins, wetlands, damp ground, fernland and adjacent pasture. It tolerates a wide range of conditions including cold or heat, wind, fire, different soil types, moderate shade, moderate salinity and the effects of grazing (Weedbusters New Zealand 2004; Auckland Regional Council 2007).

Southern Wild Rice (Z. aquatica) grows in fresh or somewhat brackish marshes, swamps, tidal mud flats, streams, and lakes. Northern Wild Rice (Z. palustris) grows on muddy shores and in shallow water of lakes and streams, often forming extensive stands (Terrell 2007).

Are there similar species?

Manchurian Wild Rice looks similar to New Zealand Raupo (Bullrush: Typha orientalis), but Manchurian Wild Rice is taller (2–3 m compared to 1–2 m for Raupo). Also, Raupo leaves are thick and spongy, have no midrib, and twist upwards, whereas Manchurian Wild Rice leaves are dry and papery, usually upright and may bend at top without twisting. It also looks similar to New Zealand Flax (Phormium spp.), but Flax leaves are much wider, smoother, thicker and shinier than those of Wild Rice (Weedbusters New Zealand 2004; Auckland Regional Council 2007).

Why Is It A Weed?

What are its impacts?

Wild Rice (Zizania sp.) is a declared weed in Tasmania. It is not naturalised in Tasmania at present but assessment has shown that Manchurian Wild Rice (Z. latifolia) and its annual relatives may have weed potential in Tasmanian wetlands, lakes and river banks. Declaration therefore assists preventative management of this plant by prohibiting its trade and requiring eradication of all occurrences (Tasmania Department of Primary Industries and Water 2008).

Native ecosystems: Z. latifolia, called Manchurian Wild Rice in New Zealand, is a serious weed of freshwater aquatic ecosystems in that country (New Zealand Plant Conservation Network 2005). Dense growth of Manchurian Wild Rice blocks waterways, impedes drainage causing flooding and disrupts recreational activities. It out-competes native water species destroying habitat for aquatic flora and fauna. It invades pasture, causing land to become waterlogged. The rhizomes penetrate and break up water banks (Auckland Regional Council 2007; Environment Walkato 2002–2007).

Zizania latifolia is also cultivated in Asia for its succulent stems and is available in parts of North America as an ornamental plant (Duke 1983; Terrell 2007). In North America, it is considered a serious threat to the native American Zizania species, as Z. latifolia is infected with the fungus Ustilago esculenta which causes swelling of the edible parts of the plant, the rhizomes and basal parts of the culms. The infection also prevents the plants from flowering and fruiting. If this fungus spread to the native species, it could have a devastating effect (Terrell 2007).

Northern Wild Rice (Z. palustris) is cultivated as a crop in some areas of the United States of America, with California being the largest producer (Terrell 2007).

Northern Wild Rice (Z. palustris) is grown as a gourmet food crop in New South Wales. Studies of this grain have shown that wild rice is rich in niacin, thiamine and riboflavin. It contains more high quality protein and lower fat content than wheat (Australian Speciality Rices undated).

How does it spread?

Manchurian Wild Rice reproduces through seed or vegetatively through rhizome extension (New Zealand Plant Conservation Network 2005). Rhizomes spread outwards slowly, but more rapid spread comes from seeds and rhizome fragments being moved by water, livestock, machinery, clothing and possibly by birds. Road graders, soil movement, dumped vegetation, contaminated diggers, farm machinery, eel nets, boats and trailers all spread seed and rhizome fragments into new areas such as catchments, lowland pasture, roadsides, water tables, drains and farm dams (Weedbusters New Zealand 2004).

The annual Southern Wild Rice (Z. aquatica) reproduces via seeds, with stands in lakes and rivers renewing themselves each year (Duke 1983).

What is its history in Australia?

Northern Wild Rice (Z. palustris) production began in Australia in 1992 (Australian Speciality Rices undated); however, the species does not appear to have naturalised (AVH 2008). Other species of Zizania are not present in Australia.

How To Manage It?

Best practice management

Methods for control of Manchurian Wild Rice include digging out plants for very small sites and spraying with chemicals for larger infestations. Rhizomes persist for years and can recover after spraying, and the seed bank may re-infest bare areas, so ongoing control is important. Eradication requires 5–10 treatments over 6–8 years (Weedbusters New Zealand 2004).

Please see the Australian Pesticides and Veterinary Medicines Authority for chemical information http://www.apvma.gov.au 

Does it have a biological control agent?

NO

When does it grow? (lifecycle/growth calendar)

In New Zealand, the perennial Manchurian Wild Rice reproduces through seed or vegetatively through rhizome extension. Plants flower from November to December and large numbers of seeds are produced in some seasons which can germinate quickly. Regrowth from underground rhizomes occurs after physical damage, fire and grazing (Weedbusters New Zealand 2004; New Zealand Plant Conservation Network 2005; Auckland Regional Council 2007).

Cultivated Manchurian Wild Rice (Z. latifolia) (more commonly known as Water Bamboo in its native range) is propagated asexually by tillers (daughter shoots that sprout from the parent plant) in Asia. Field plantings in the sub-tropical northern hemisphere are made in later summer through to early autumn and in the temperate regions, in autumn. Harvest is made in about 150–170 days from planting. Harvest must be made before the fungus, Ustilago esculenta, goes into the reproductive phase when the black smut (spores) is produced (Yamaguchi 1990).

In Australia, cultivated annual Northern Wild Rice (Z. palustris) seed is planted in spring or autumn. The soil needs to be saturated from the time the seeds germinate until 2–3 weeks before harvest. Immature seeds are green, but turn a purple-black colour as they reach maturity. Seeds on any given stem mature at different times, and on the secondary stems, they mature later than on the main stems. Early-maturing seeds are very prone to shattering (dropping from the seed head) before the later-maturing seeds ripen (Fletcher 1999).

Where Is It Found?

Which states and territories is it found?

NSW

What areas within states and territories is it found?

Only one species of Wild Rice, Northern Wild Rice (Z. palustris), occurs in Australia, in cultivation in New South Wales (Australian Specialty Rices undated).

Where does it originate?

Manchurian Wild Rice (Z. latifolia) is a rhizomatous perennial, native to Asia, extending from north-east India and Russia through China and Myanmar to Korea and Japan. Southern Wild Rice and Northern Wild Rice, both annuals, are important constituents of aquatic plant communities in North America, providing food and shelter for numerous animal species. Southern Wild Rice is native from the central plains to the eastern seaboard of North America. Northern Wild Rice grows mostly to the north of Southern Wild Rice, but the two species overlap in the Great Lakes region, eastern Canada, and New England. Texas Wild Rice (Z. texana), a perennial, is listed federally as an endangered species in the United States of America. It grows only in the headwaters of the San Marcos River, in San Marcos, Texas (Terrell 2007).

National And State Weed Listings

Is it a Weed of National Significance (WONS)?

NO

Where is it a declared weed?

TAS, WA

Government weed strategies and lists – Weeds Australia

Is it on the National Alert List for Environmental Weeds?

NO

Government weed strategies and lists – Weeds Australia

Is it on the Agricultural Sleeper List?

NO

Government weed strategies and lists – Weeds Australia

Names And Taxonomy

Main scientific name

Zizania spp.

Other scientific names (synonyms)?

Does it have other known common name(s)?

Manchurian Wild Rice, Asian Wild Rice, Water Bamboo, Texas Wild Rice, Northern Wild Rice, Southern Wild Rice