Arrowhead is a fast growing water weed with distinct, arrow-shaped leaves. It chokes waterways and irrigation channels.
Arrowhead grows quickly and forms dense infestations in wetlands and natural watercourses where it can:
It is also a weed in irrigation channels where it:
Arrowhead is most visible in summer and dies back in winter. It grows in two forms. One form is beneath the water as a submerged rosette. The other form is an emergent plant up to 1 m tall above the waterline. Most seedlings appear in spring.
There are two forms of leaves.
Leaves above water are:
Leaves under the water are:
Annual plants have fibrous roots. Perennial plants have a short thick rhizome.
Arrowhead looks similar to these two weeds:
It also looks similar to two Australian native plants:
Most arrowhead in NSW grows in the Riverina region. It grows in rice crops and irrigation channels.
It was first recorded in Australia as a garden escape near Sydney in 1926. During the 1960s arrowhead spread to the Murrumbidgee Irrigation Area.
Arrowhead is native to North and South America.
Arrowhead is usually found in shallow, warm, slow-moving and stationery waters including:
Each plant can produce hundreds of thousands of seeds. Seed can float for up to 3 weeks before sinking. Water, birds and other animals spread the floating seeds. Seeds can either sprout immediately or remain dormant until conditions are right for germination.
New arrowhead plants can grow from stem or root fragments.
Adair, R. J., Keener, B. R., Kwong, R. M., Sagliocco, J. L., & Flower, G. E. (2012). The Biology of Australian weeds 60.'Sagittaria platyphylla' (Engelmann) J.G. Smith and 'Sagittaria calycina' Engelmann. Plant Protection Quarterly, 27(2), 47.
Aquatic Plant Services. (2004). The Biology and Control of Arrowhead, Goulburn-Murray Water.
Chapman, M. & Dore, D. (2006). Arrowhead Strategic Plan Final Draft, Gommalibee, Victoria: Rural Plan Pty Ltd.
Crocker, W. (1907). Germination of seeds of water plants, Botanical Gazette, Vol. 44, No. 5, pp. 375-380.
Department of Primary Industries Victoria. (2009). Invasiveness assessment - Giant Arrowhead (Sagittaria montevidensis) in Victoria, August 2010.
Eastern & Western Riverina Noxious Weeds Advisory Group. (2004). Regional Weed Management Plan: Riverina Sagittaria Management Plan
Flower, G. (2003). The Biology and Control of Arrowhead (Sagittaria graminea). River & Catchment Health: Presenting current research in the Goulburn Broken Catchment.
Goulburn-Murray Water. (2001). Arrowhead Sagittaria graminea factsheet, Aquatic Plant Services.
Gunasekera, L. & Krake, K. (2001). Arrowhead – a serious aquatic weed in northern Victoria. In Victorian Landcare and Catchment Management, 19, 7.
Rataj, K. (1972). Revision of the genus Sagittaria. Part I. (Old World Species), Annotationes Zoologicae et Botanicae, 76, pp. 1-36.
Turner, C.E. (2001). Reproductive Biology of Sagittaria monetividensis Cham. & Schlecht. spp. Calycina (Engelm.) Bogin (Alismataceae), Unpublished doctoral dissertation, University of California, Berkeley.
Successful weed control requires follow up after the initial efforts. This means looking for and killing regrowth or new seedlings. Using a combination of control methods is usually more successful.
To tackle arrowhead:
Arrowhead can be excavated with machinery or dug out by hand.
Physical removal is useful for:
Remove all plant fragments including roots and rhizomes. Ensure plant fragments can’t float downstream.
Use appropriate hygiene and containment practices. Hygiene includes removing all plant material and soil from machinery and equipment before leaving the site. Bunding, fences or screens will contain arrowhead and prevent it from moving downstream.
Excavation can be labour intensive and costly. It is generally avoided in irrigation channels where it interferes with the engineering structure of the drain. However, for new isolated infestations, eradication is possible using mechanical or manual removal if followed by checking and removal of regrowth.
Only use products with label approvals for aquatic use.
Herbicides supress arrowhead infestations. They cause the base of the stem to detach from the plant, which kills the leaves and stems above the water. Foliar applied herbicides do not generally kill the underwater parts of the plant, especially for plants in deep water.
For the best results apply herbicides when water levels are low and plant growth is high. This will enable maximum uptake of the herbicide.
See Using herbicides for more information.
PERMIT 9907 Expires 31/03/2025
Glyphosate 360 g/L
(Only products registered for aquatic use)
Rate: One part product to 50 parts water
Comments: Spot spray.
Withholding period: Nil.
Herbicide group: M, Inhibitors of EPSP synthase
Resistance risk: Moderate
PERMIT 9907 Expires 31/03/2025
Glyphosate 360 g/L
(Only products registered for aquatic use)
Rate: One part product to 9 parts water
Comments: Splatter gun.
Withholding period: Nil.
Herbicide group: M, Inhibitors of EPSP synthase
Resistance risk: Moderate
The content provided here is for information purposes only and is taken from the Biosecurity Act 2015 and its subordinate legislation, and the Regional Strategic Weed Management Plans (published by each Local Land Services region in NSW). It describes the state and regional priorities for weeds in New South Wales, Australia.
Area | Duty |
---|---|
All of NSW | General Biosecurity Duty All pest plants are regulated with a general biosecurity duty to prevent, eliminate or minimise any biosecurity risk they may pose. Any person who deals with any plant, who knows (or ought to know) of any biosecurity risk, has a duty to ensure the risk is prevented, eliminated or minimised, so far as is reasonably practicable. |
Hunter |
Regional Recommended Measure* (for Regional Priority - Prevention)
Land managers should mitigate the risk of the plant being introduced to their land. Land managers should eradicate the plant from the land and keep the land free of the plant. A person should not deal with the plant, where dealings include but are not limited to buying, selling, growing, moving, carrying or releasing the plant. Notify local control authority if found. |
North West |
Regional Recommended Measure* (for Regional Priority - Prevention)
Land managers should mitigate the risk of the plant being introduced to their land. Land managers should eradicate the plant from the land and keep the land free of the plant. A person should not deal with the plant, where dealings include but are not limited to buying, selling, growing, moving, carrying or releasing the plant. Notify local control authority if found. |
Western |
Regional Recommended Measure* (for Regional Priority - Prevention)
Land managers should mitigate the risk of the plant being introduced to their land. Land managers should eradicate the plant from the land and keep the land free of the plant. A person should not deal with the plant, where dealings include but are not limited to buying, selling, growing, moving, carrying or releasing the plant. Notify local control authority if found. |
*To see the Regional Strategic Weeds Management Plans containing demonstrated outcomes that fulfil the general biosecurity duty for this weed click here |
Reviewed 2023