Common name: Arrowhead

Arrowhead or Swamp Potato is a water plant originating from China and cultivated for its corms, which are cooked as a vegetable.

It grows partially submerged in clumps 0.5 to 1 m (1.5 to 3 ft) tall, with light green, erect herbaceous stems that hold large arrowhead-shaped leaves above the water. The corms are attached to the roots, which are submerged and anchor the plant firmly in the wet soil or mud.

The flowers are white, but the plant rarely flowers or sets seed. Each clump produces about six to ten small, onion-shaped corms with an elongated beak. They have thin, light brown skin and crisp, white, starchy flesh similar to a potato.

Edible uses

Cooked vegetable - The corms are edible but must be cooked before eating. They roast well and taste potato-like.

Chip or crisp - The corms can also be peeled, thinly sliced, and deep-fried into a crisp, potato-chip-like snack that is especially popular during Chinese New Year festivities. Fresh corms have 16 to 23% starch and 4 to 7% protein.

Environmental uses

Wastewater treatment - Sagittaria species tolerate and assimilate high nutrient levels, particularly phosphorus. This makes them good candidates for wastewater treatment systems, including wastewater catchments designed to capture and treat stormwater runoff, and...

Land rehabilitation - ...for wetland creation, enhancement, and restoration projects.

Water garden plant - The plant is also well suited for cultivation in water gardens. However, its ability to spread vegetatively and become a weed has discouraged cultivation outside its natural range.

Climate

Grows well and is productive under submerged conditions in subtropical and tropical climates, generally areas with annual lows of 11 to 25°C, annual highs of 21 to 35°C and where there is permanent surface water, such as a pond or lake.

Growing

Where it is not a weed risk or prohibited, new plants grow easily from corms, which are planted in rich soil and covered with shallow water 10 to 30 cm (4 to 12 in) deep. It's best to grow the plants in large containers to help contain their spread. Corms are planted in spring, or at the start of the rainy season when air humidity is high.

It performs best in loose, friable, well-manured loam soils that are moderately acidic to slightly alkaline (generally pH 6.0 to 7.5) and in sites with full- to partial sun exposure. The corms are harvested when the leaves turn yellow and die back, or generally about six to seven months after sowing.

Problem features

Arrowhead is listed as a weed in the Global Invasive Species Database and other weed reference publications. Many countries describe it as a general nuisance in wetland crops, irrigation systems, drains, and waterways. The seed, although rarely produced by the plant, floats and is dispersed over long distances by flowing water. Plants also spread locally from vegetative material, including whole immature plants and underground corms.

Books

• Bladholm, L. 1999, The Asian grocery store demystified, 1st edition, Renaissance Books, Los Angeles, California

• Burke, D. 2005, The complete Burke's backyard : the ultimate book of fact sheets, Murdoch Books, New South Wales, Australia

• Hanson, B. 2007, Buried treasures : tasty tubers of the world : how to grown and enjoy root vegetables, tubers, rhizomes, and corms, Brooklyn Botanic Garden, Brooklyn, New York

• Herklots, G. A. C. 1972, Vegetables in south-east Asia, Allen and Unwin, London

• Macmillan, H. F. 1943, Tropical planting and gardening : with special reference to Ceylon, 5th ed, Macmillan Publishing, London

• Morgan, D. & Achilleos, A. 2012, Roots : the definitive compendium with more than 225 recipes, Chronicle Books, San Francisco

• Nash, H. & Slocum, P. D. & Stroupe, S. & Romar, B. 2003, Complete guide to water garden plants, Stirling Publishing, New York

• Norrington, L. & Campbell, C. 2001, Tropical food gardens : a guide to growing fruit, herbs and vegetables in tropical and sub-tropical climates, Bloomings Books, Hawthorn, Victoria

• Perkins, K. D. & Payne, W. 1981, Guide to the poisonous and irritant plants of Florida, Florida Cooperative Extension Service, Gainesville, Florida

• Randall, R. P. 2007, The introduced flora of Australia and its weed status, Cooperative Research Centre for Australian Weed Management, Glen Osmond, South Australia

• Rubatzky, V. E. & Yamaguchi, M. 1997, World vegetables : principles, production, and nutritive values, 2nd ed., Chapman & Hall, New York