Watermeal (Wolffia columbina)

Watermeal and Duckweed

Watermeal & Duckweed in pond

BIOLOGY:

Watermeal is considerably smaller than Duckweed, being about 1/32 of an inch in width or about the size of a pinhead. It has no root  and obtains nutrients thru the underside of the floating frond. Duckweeds, including watermeal, generally reproduce by a process called budding in which a new daughter bud is produced every day or so. In two weeks under ideal summer growth conditions, a single parent plant and its subsequent “daughters” can result in the production of up to 17,500 plants. It is this very rapid budding process that allows duckweeds to quickly cover a pond in just a few weeks.

HABITAT:

Both duckweeds and watermeal are typically found in quiet, nutrient rich wetlands and ponds. These plants require high levels of nutrients to “bud” profusely and thus, are indicators of ponds receiving excessive nutrients. Quite often, problem populations are located in or near woodlots, which not only provide the quietness preferred by this plant but also provide a rich, organic source in the form of tree leaves. Bottom sediments of infested ponds are best described as having a smelly, black ooze bottom, which can provide a valuable nutrient source for the plants. Older ponds tend to experience nuisance infestations more frequently because of the build-up of bottom organic matter.

Not all nutrient-rich ponds experience duckweed problems. Duckweeds and watermeal do not tolerate moving water. Thus, “unprotected” ponds that are windswept or ponds with considerable water flow-through do not typically experience nuisance populations of either genus. Apparently, these plants are fragile and require almost stagnant waters to flourish.

IDENTIFICATION TIPS:

• Free floating
• Color is shiny deep or lime green
• Size is about half the size of a grain of rice, sometimes no larger than poppy seed.
• Shape is slightly elliptical or round.
• Wolffia has no root structure. Place a finger or two into the water and withdraw it, your fingers will be coated with these small distinct green bb’s. Rub your thumb and forefinger together, they will feel like miniature ball bearings