Giant or big duckweed is still relatively small (1/16 to 1/4 inch) with 1 to 4Â leaves, or fronds, light green in color. Three or moreÂ rootsÂ (or root-hairs) protrude from each frond. Duckweeds tend to grow in dense colonies in quiet water, undisturbed by wave action. Often more than one species of duckweed will be associated together in these colonies. Giant duckweed can be an aggressive invader of ponds and are often found mixed in with other duckweeds, mosquito fern, and/or watermeal. If colonies cover the surface of the water, then oxygen depletions and fish kills can occur. These plants should be controlled before they cover the entire surface of the pond.