What is Duckweed, and is it Good?

Common duckweed, or Lemna minor, is a small flowering, floating plant that sits on the surface of still ponds or lakes. Identifying this plant is difficult and people often confuse it with watermeal.

Duckweed, also called water lentils, can overwhelm an area if not controlled. This occurs because the plants grow incredibly fast and cause negative environmental impacts if left untouched. There are benefits to allowing duckweed to grow in certain conditions.

What Does Duckweed Look Like?

Individual duckweed plants float on the water and resemble a clover. Green leaves have fronds, or sections, that grow one-sixteenth to one-eighth of an inch long; leaves are oval or egg shaped. The roots look like hair hanging in the water about an inch long. Duckweed grows flowers that can only be seen through magnification.

Duckweed plants may attract spiders, flies, and possibly bees who spread the plant’s pollen. Water lentils are often mixed with other floating plants in ponds.

The biggest mistake while treating duckweed is plant misidentification. Duckweed is often confused with watermeal, another small floating light green plant. Watermeal looks like cornmeal or strawberry seeds; each plant is about the size of a pencil tip and can be round or oblong. Duckweed is larger than watermeal and typically has three fronds per plant.

Is Duckweed Edible?

It is safe to eat and is high in protein and minerals. Duckweed may have contaminants; concerns exist about the amount of calcium oxalate found in the plant.

What Eats Duckweed? Do Ducks Eat Duckweed?

Many animals depend on Lemna varieties in their diets. Some fish, birds, and mammals such as beavers or muskrats consume duckweed.

Ducks consume duckweed, although it is not the main item in their diets. Ducks are omnivores and will eat insects and fish among other things.

Is Duckweed Harmful?

Dense populations of this plant can damage ecosystems and the environment, blocking water flow, oxygen exchange, and sunlight. When oxygen levels drop, fish and plant life are at risk.

Effects on Ecosystems and the Environment

Duckweed is the leading cause of greenhouse gas emissions in ponds. Methane gas forms if oxygen production levels fall short.

Over-population of water lentils creates imbalances within ecosystems. The plants can thrive without sunlight, absorbing vital nutrients other plants need. Fish may experience hypoxia, low oxygen levels in the body, leading to death.

Is Duckweed Invasive?

Duckweed is native but can be aggressive in nutrient rich waters. It can invade spaces rapidly as it can double in its size in just 16-48 hours.

How Does Duckweed Reproduce?

Water lentils repeatedly clone themselves through asexual reproduction. Each leaf produces new buds near the center, which grow into new leaves and then detach from their parent leaves. These detached leaves then begin to produce leaves of their own.

How Fast Does Duckweed Grow?

Duckweed can take over bodies of water fast, doubling its mass within 16-48 hours depending on weather and water conditions.

Can Duckweed be Helpful?

Lemna minor shades the water, providing shelter for small fish and amphibians. These bait fish and other small animals are food sources for larger fish, birds, and mammals. 

Remember to Keep Duckweed Under Control

While duckweed can be helpful in small quantities, it should be controlled so it doesn’t take over a body of water. When its populations dominate a pond or lake, they can cause negative impacts on the water’s ecosystem and the environment. Consider options for controlling duckweed on our Weed Control page.