How to Grow and Care for Duckweed

Duckweed (Lemna spp.) is one of the smallest flowering plants on Earth. Adaptable to a wide range of temperatures, it can be grown outdoors on home ponds and indoors, near a sunny window, in large aquariums. As long as it receives lots of light and resides in calm water, duckweed is an easy plant to grow.

Duckweed Care

Because this aquatic plant can be nourished by the air, it is a very easy plant to grow indoors and outdoors. Here are the main care requirements for Common Duckweed.

• Provide full sun, at least six hours a day.
• Maintain calm water with little to no movement so the plant can grow.
• Feed with a balanced fertilizer.
• Keep its environment well-oxygenated. Rake or skim any excess duckweed off the top of the water periodically.
  

Light

Full sun is needed for best results, but the plant will tolerate low to high light and soft or hard water. Set the aquarium in a warm, sunny location where it receives at least six hours of sunlight every day if possible. High-quality, full spectrum light and the addition of trace minerals during water changes will encourage denser growth.

Water

Common Duckweed grows quickly, floating on the surface of calm water. Keep the water calm with little to no current; if the water moves too much, the plant will not grow quickly.

To cultivate duckweed, use a rectangular container that's a minimum of 5 inches deep, 18 inches long, and 12 inches wide. Add dechlorinated water and blow air using a straw until the water shows signs of oxygenation. Check the pH level and add the duckweed. To harvest, use a fish net or coffee filter to scoop the growing duckweed and transfer it to a fish tank, aquarium, or pond.

Fertilizer

Add a balanced 10-10-10 liquid fertilizer that has iron, likely found at an aquarium store. Dilute the fertilizer with four to five times the normal amount of water.

Temperature

Common Duckweed is adaptable to temperature. For best results, maintain a temperature between 63 to 79 degrees Fahrenheit.

Types of Duckweed

• Least Duckweed (Lemna minuta): The smallest of the Lemna, it has a single oval-shaped leaf and produces a membrane-found flower.
• Fat Duckweed (Lemna gibba): Resembling the common variety, this type has flattened fronds bur carry large air spaces between them.
• Greater Duckweed (Spirodela polyrhiza): Scattered widely across certain wetlands this type of duckweed has fronds that carry a reddish tone.
• Ivy-leaved Duckweed (Lemna trisulca): This type of duckweed differs visually from others in its angular leaves and tendency to float just below the water's surface.

Pruning

Because duckweed grows so quickly, complete control of its invasiveness is impossible. Start prevention early in spring before the spread becomes a nuisance. Here are several ways to control and prevent invasive growth:

• Rake or net small ponds repeatedly and compost the removed weed.
• Use a floating boom to sweep larger pools from end to end, regularly from early spring to winter dormancym
• Put stop-boards at any upstream inlets to prevent duckweed from spreading to other ponds or lakes.
• Welcome weed-eating water birds like domestic or ornamental ducks, moorhens, and coots, or grass carp fish to quickly eat the plants.
• Shade duckweed beneath tall, bushy plants, water lilies or other plants with floating leaves to reduce growth.
• Use a fountain to gently disturb the surface of the water.

Although duckweed's spreading nature is considered invasive, many gardeners would agree the benefits outweigh the maintenance. This nutritious plant keeps many creatures well-fed, and it removes pollutants from the water, making it an ideal specimen for any aquarium or pond.

Propagating Common Duckweed

Common Duckweed is often propagated by division or fragmentation. Here's how:

1. Separate clusters into small sections making sure that each has some fronds and some roots
2. Transfer divided or fragmented duckweed to a similar environment with the same water pH and temperature for the quickest adaptation.
3. Space the fragmented fronds out as much as possible, as overcrowding can hinder growth.
4. Monitor nutrients and make sure the new environment receives plenty of light for optimal growth.

Common Pests & Plant Diseases

Some pests that are unique to duckweed include the weevil and the Lemna fly. Prevention is always the best line of defense so inspect the fronds on a regular basis before you have a full infestation on your hands. Make sure water is properly circulated, and consider adding beneficial insects such as ladybugs. If you've already identified a pest problem, apply neem oil or insecticidal soap directly to the areas affected. Bacterial canker and fire blight can also affect duckweed.