Outdoor experiments were conducted at two locations in Minnesota to characterize the growth, development, and vegetative reproduction potential of giant burreed grown with and without wild rice. Giant burreed growth was influenced by environment more than the presence of wild rice. Shoots emerged from corms 2 to 3 wk after planting (WAP), and continued throughout the growing season. Giant burreed attained a maximum height of 135 cm with an average 36 shoots/plant. Rhizome production started 4 to 6 WAP, and continued throughout the growing season. Corm formation at the base of shoots started 8 WAP and continued throughout the growing season. Rhizomes grew to a maximum cumulative length of 2500 cm/plant spreading in all directions and produced up to 250 buds/plant. Corm and rhizome bud viability was 15 and 10%, respectively. These data suggest that giant burreed grown in wild rice should be controlled by 2 to 3 wk after emergence to prevent vegetative reproduction.

The response of giant burreed to bentazon, propanil, 2,4-D (amine salt), and 2,4-D plus crop oil (0.5% v/v) was evaluated at the 2-aerial-leaf stage of wild rice. Bentazon, 2,4-D, and 2,4-D plus crop oil at 1.1 kg/ha or more in 1984, and propanil and 2,4-D plus crop oil at 4.5 kg/ha in 1985 reduced giant burreed dry weight. Generally, herbicide rates above 1.1 kg/ha injured wild rice and reduced yields compared to weed-free controls. None of the study treatments resulted in effective giant burreed control without unacceptable injury to wild rice.