Greater duckweed: complete guide

Overview

The Greater duckweed (Spirodela polyrhiza) is an aquatic water plant from various parts of the world, distributed cosmopolitanly. This member of the Araceae family is known as a fast-growing, free-floating water plant that offers many benefits for ponds and aquariums. With its numerous hanging roots and small leaf-discs, it's a fascinating water plant.

Greater duckweed is easy to care for in the right aquatic environment. With good water and sufficient sunlight, this plant will grow rapidly. It's also called 'water flaxseed' because of its copious seeds. This is a useful plant for both fish ponds and ornamental gardens.

Appearance and growth

Greater duckweed consists of small, green, oval leaf-discs that grow tightly together. Each leaf-disc carries multiple long, hair-like roots that hang in the water. These hanging roots are the most characteristic feature of this plant - hence the name 'greater duckweed'.

The plant usually reaches a size of only a few millimeters to about 1 centimeter in diameter per leaf-disc. The plant grows rapidly through vegetative reproduction, with new leaf-discs forming on the mother plant. Under ideal conditions, the population can double in weeks.

Ideal location

Greater duckweed grows best in water with plenty of sunlight. This can be a pond, aquarium, or even a large water basin. The plant loves growing in full sun or bright lighting. At least 4-6 hours of direct sunlight per day is recommended.

Make sure the water isn't too turbulent, as the plant does best in still or slowly moving water. In aquariums, filter flow must be adjusted so the plant isn't constantly in currents.

Water conditions

Greater duckweed grows in almost any type of water, from fresh to slightly brackish. The plant is not very fussy about water quality, although clean, uncontaminated water is better. Water quality doesn't need to be perfect - this is actually an advantage because the plant tolerates much contamination.

Optimal water temperature is between 15 and 25 degrees Celsius. Cooler temperatures slow growth, while hot summers can accelerate it. It can grow in both still and running water, although still water is better.

Nutrition and feeding

Greater duckweed gets much nutrition from the water and from animal waste. In aquariums with fish, the plant usually gets enough nutrition without supplemental fertilizing. In pure water basins, supplemental feeding can be useful.

The plant is very useful for filtering excess nutrients, especially nitrogen and phosphorus. This helps prevent algal growth. In fish ponds, this plant can contribute to biological filtration mechanisms.

Maintenance and control

Greater duckweed requires minimal maintenance. However, it can grow quickly and cover large water surfaces. Regular thinning of the population is needed if you want to prevent explosive growth. Simply remove extra leaf-discs and discard them.

Make sure the plant doesn't cover the entire water surface, as this blocks oxygen and light for other water organisms. A coverage of about 30-50% of the water surface is ideal.

Seasonal calendar

• March-April: Growth begins to slow after winter. Water begins to warm. Population grows slowly.
• May-June: Peak growth period. Regular thinning needed. Sunshine stimulates rapid growth.
• July-August: Growth remains strong. Thinning tasks increase. Heat and sunlight favor growth.
• September-October: Growth begins to slow. Water cools. Less thinning needed.
• November-December: Growth slows significantly. Plant may disappear or barely survive. In cold climates, winter dormancy may occur.
• January-February: Winter dormancy. Very slow or no growth. Minimal care needed.

Ecosystem benefits

Greater duckweed offers many benefits in aquatic ecosystems. It provides food for waterfowl, fish and insects. The plant absorbs excess nutrients and helps reduce algal growth. The hanging roots provide shelter for small fish and aquatic animals.

In fish ponds, this plant helps maintain biological balance. It helps naturally purify and filter wastewater.

Combinations and tankmates

Greater duckweed can grow with other water plants, although competition is possible. Other floating plants you can keep together include water lettuce, seagrass and other duckweed species.

In aquariums it can grow with many fish, although larger fish may eat it. It's a good plant for peaceful communities.

Summary

Greater duckweed is a valuable aquatic plant for ponds and aquariums. With rapid growth, minimal care requirements and many benefits for aquatic ecosystems, it's a practical choice. Provide regular thinning to prevent overgrowth, and you'll have healthy water plant coverage.

Want more insight into water plants? Visit gardenworld.app for more plant guides for your water garden design.