SMARTWEED 



Polygonum spp. 



Smartweed may be entirely aquatic, marginal, or amphibious; the 

 same plant may even have portions under water with some branches 

 erect on land. This extremely adaptable plant easily becomes a pest 

 in irrigation systems and other bodies of water by displacing and 

 transpiring large amounts of water. With approximately 320 species, 

 smartweed grows under various ecological conditions around the world. 



The many species of smartweed share some common 

 characteristics. The terrestrial forms are erect, or sometimes vine-like, 

 but lack tendrils. The aquatic forms are emergent with floating leaves 

 and stems. The stems of either forms can be simple or branched, but 

 they usually have swollen joints and sheaths around the stem at each 

 leaf base. The amount and type of plant hair varies tremendously 

 among the species, however the aquatic forms are hairless. The simple, 

 alternate leaves have smooth margins. Individual flowers are borne on 

 short stalks which are clustered together along the main stem creating 

 terminal spikelike floral structures (insert 1). The perfect flowers 

 (having both male and female structures) have four to six petals and 

 are pink, green, or white. The hard, dry, one-seeded fruits are either 

 triangular or lens-shaped in cross section, and vary in color from 

 light-tan through reddish-brown to black (insert 2). Roots can reach 

 lengths of 9 to 15 meters, making control efforts very difficult. 



The seeds of smartweed are eaten by a variety of birds and small 

 mammals. An aquatic area infested by smartweed is often a popular 

 feeding area for waterfowl. 



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