Mermaid Weed Care Guide – Planting, Growing, and Propagation

Mermaid Weed (Proserpinaca palustris) – Detailed Guide Care, Diet, and Breeding main

Proserpinaca palustris, commonly known as Mermaid Weed, draws attention with its color palette and leaf shapes. This plant can easily display a range of yellow, red, orange, and even various shades of green.

I need to start off by saying that Mermaid Weed is actually more suited for outdoor tanks.  Growing this plant in aquariums can be challenging due to its specific requirements (cool, soft to moderate water, a nutrient-rich substrate, CO2, and ample lighting). Without these conditions, success may be limited or the plant may struggle to reach its full growth potential.

In this article, I will summarize everything known about Mermaid Weed from both the aquarist’s perspective and scientific data including care, maintenance, propagation, common issues, and more.

Quick Notes about Mermaid Weed

Common Name Mermaid Weed
Other Names Marsh mermaidweed
Scientific Name
Proserpinaca palustris
Difficulty Medium
Lighting Moderate-High 
Optimal pH 5.5 – 7.5
Optimal GH 2 – 8
Optimal Temperature 59 – 86°F (15 – 30°C)
Substrate Nutrient-rich
Can Be Grown Emersed
Yes
Growth Rate Slow to moderate
Placement in Tank
Midground and background
Aquarium size 20+ inches (over 50 cm)
Fertilizers
Needed
CO2 Needed
Propagation Vegetative by cuttings
Color
Red, yellow, orange, and green

Etymology

The genus name “Proserpinaca” derives from Latin referring to Proserpina. As the Roman goddess of the underworld and spring, who is associated with growth and vegetation.

Note: There is a direct analogy with Greek myths. Pluto (the equivalent of Hades), king of the Underworld, complained to Jupiter (the Roman counterpart of Zeus) about not having a wife. Jupiter promised him Proserpina (the equivalent of Persephone), his daughter the goddess of grain and harvests.

This species name “Palustris” also comes from the Latin word “Palus”, meaning “Swamp”. It indicates that the plant is commonly found in marshy or swampy areas.

Note: I believe that the choice of name was also influenced by the plant’s ability to thrive in waterlogged or marshy conditions, symbolizing a connection between life (vegetation) and death (swampy areas).

Taxonomy

  • Kingdom: Plantae (Plants)
  • Clade: Angiosperms (Flowering plants)
  • Clade: Eudicots (Two seeds)
  • Order: Saxifragales (Order of flowering plants)
  • Family: Haloragaceae (Watermilfoil family/aquatic and semi-aquatic plants)
  • Genus: Proserpinaca
  • Species: Proserpinaca palustris

Proserpinaca palustris has three subspecies:

  1. Proserpinaca palustris var. amblyogona;
  2. Proserpinaca palustris var. palustris;
  3. Proserpinaca palustris var. crebra. 
Despite being often sold under the name “Proserpinaca palustris “Cuba”, it’s just a commercial label and not a distinct subspecies.

Distribution of Mermaid Weed

Mermaid Weed (Proserpinaca palustris) – Detailed Guide Care, Diet, and Breeding - destributionProserpinaca palustris is found across various regions in North America, including the United States and Canada.

In the United States, it is distributed in states such as Alabama, Arkansas, Delaware, Florida, Georgia, Illinois, Kentucky, Louisiana, Massachusetts, Maryland, Michigan, Missouri, Mississippi, North Carolina, New Jersey, New York, Oklahoma, Pennsylvania, Rhode Island, South Carolina, Tennessee, Texas, Virginia, Wisconsin, and West Virginia.

Additionally, it can be found in Canadian provinces like New Brunswick, Ontario, and Quebec, as well as in countries such as Jamaica, Cuba, the Bahamas, Mexico (specifically in the states of Chiapas and Veracruz-Llave), Guatemala, El Salvador, and Colombia.

Habitat of Mermaid Weed

Proserpinaca palustris is a freshwater plant. It generally grows in shallow swamps, ponds, or temporary pools.

This plant tolerates a submerged condition remarkably well but also needs air-breathing intervals for its life cycle.

Description of Mermaid Weed

This plant is a polymorphic, aquatic to semi-aquatic, perennial and long-stemmed plant. With its bushy foliage, Proserpinaca palustris makes an impressive mid and background plant in the aquarium.

This plant grows with submersed and emersed plant parts.

Mermaid Weed (Proserpinaca palustris) – Detailed Guide Care, Diet, and Breeding emersed form
Submersed form

Submersed form.

  • Size. The height can reach up to 20+ inches (50 cm). The width of the bush can extend up to 6 inches (15 cm). The stem is about 0.1 inches (3 mm) in thickness.
  • Leaves. The leaves are elongated, serrated, and toothed, resembling needles (comb-like teeth) that fan around the stem. They can have small serrations or deep incisions, reaching lengths of up to 1.6 inches (4 cm) and widths of 1.2 inches (3 cm). They are very soft and tender. They are thin with a central rib and three to five narrow lobes.
  • Internodes. The internode spacing ranges from 2 to 3 cm, giving the stem a lush appearance.
Mermaid Weed (Proserpinaca palustris) – Detailed Guide Care, Diet, and Breeding - submersed form
Emerged form

Emerged form.

  • Size. The stem of this plant loses flexibility, becoming creeping and woody as it develops a rhizome. It can extend up to 30+ inches (80 cm) in length.
  • Leaves. When grown out of water, the leaves become elliptical with slight serration, firmer texture, and darker green color, measuring 1.2 – 2.4 inches (4 – 6 cm) long and 0.4 – 0.6 (1-1.5) cm wide.
  • Flowers. This is a flowering plant. However, if the plant is completely submerged it does not produce inflorescences.

The flowers are located between the upper side of a leaf or stem and the supporting stem or branch. They have 3 tiny petals forming a cup shape, with 4 stamens and a pistil. The fruits are 3-4 mm thick and may hold 3 or 4 seeds.

In emersed form, the plant is quite unattractive and rather dull. The leaves transition from a plain green to an olive hue and lose their serrated edges.

However, when submerged, this beauty becomes the highlight of any aquarium.

For a more detailed and scientific description of Proserpinaca palustris, you can read here.

Tank Requirements and Water Parameters

Opinions on the difficulty of growing Proserpinaca palustris vary. However, most aquarists consider it to have at least a moderate level of difficulty.

In aquariums, this plant can be quite finicky. It has specific requirements for water conditions, lighting, and nutrients.

However, when grown outdoors (emersed form), Mermaid Weed becomes pretty hardy and does not require too much more attention and care. Notably, in its natural habitat, it is considered a weed.

Tank size:

The recommended tank size for growing Mermaid Weed is a minimum of 10 gallons (~40 L). Because of its growth potential, tall tanks are better than long tanks for this plant.

Water type, Temperature, Hardness, and pH:

Temperature: Mermaid Weed will thrive in a broad temperature range from 60 – 86°F (15 – 30°C), making it suitable for cold-water aquariums.
Even more, it was noticed that at high temperatures >82°F (28°C), the internodes become long regardless of the amount of light. At 64 – 77°F (18 – 25°C), the plant looks much more decorative.

pH: This plant prefers a slightly acidic pH in the range of 5.5 – 7.5.
Hardness: It grows better in soft and medium water GH 2 – 8 and KH 1 – 4.

Lighting: 

The lighting should be strong as Mermaid Weed loves light and dies in the shade.

Under good lighting, the leaves acquire a beautiful Red-copper color, making the plant a pleasant contrast with other plants. In low lighting, it has green leaves and an unattractive thick stem, about twice as thick as under optimal conditions.

According to the study, it tends to grow juvenile (undeveloped) leaves with an 8-hour light cycle, generative leaves with a 12-hour light cycle, and generative leaves and flowers with a 14-hour light cycle.

If light does not reach the lower part of the stem, it drops the lower leaves. Additionally, the plant also tends to drop its lower leaves when the upper stem reaches the surface.

In one study, the influence of natural light in an aquarium versus natural light outdoors was compared. An aquarium was placed on a windowsill where it received constant sunlight.

The final results showed that this plant grew less, slower, and displayed different colors compared to plants growing nearby outdoors.
This is because aquarium glass still absorbs a significant portion of the light, affecting the spectrum that reaches the plant. It’s believed that the red and blue spectra are crucial for bringing out the plant’s vibrant colors.

Related articles:

Flow:

In nature, Mermaid Weed grows in stagnant waters. It does not like it very much.

Substrate:

This plant is a heavy root feeder. If the substrate is inadequate, the stem blackens and the plant deteriorates.

Therefore, a nutrient-rich substrate is ideal because it supports the plant’s growth by providing the most nutrients.

The substrate depth should be at least 2 inches (5 cm) since the root system is well-developed. It does not tolerate root trimming well.

Related article:

CO2 and fertilization:

CO2: Although some aquarists have managed to grow Mermaid Weed without CO2, it’s more of an exception. Without CO2, you will not achieve the bright red-yellow coloration that this plant is known for.

Therefore, you will need to use CO2. However, high CO2 concentrations can also cause morphological mutations in the leaves, making them thinner with elongated teeth.

Fertilization: Proper and regular fertilization, as well as the right concentration of CO2, is crucial. A deficiency in iron and/or potassium results in overall discoloration and leaf loss.

Although this plant is not demanding of phosphates but reacts negatively to an excess of nitrates 

Important: It is crucial to maintain a proper balance of CO2 and nutrients for high-light demanding plants. Using intense lighting without CO2 injections and/or fertilization is not recommended, as it can lead to significant plant issues (including algae).

Related article:

It is recommended to regular dose of liquid plant fertilizers (2-3 times a week) and root tabs (periodically). Macro and micronutrients will help to sustain healthy growth and ensure that the plants maintain the best coloration.

Note: If you keep shrimp in the tank with Mermaid Weed, I would highly recommend reading my articles:
CO2 in a Planted Tank Guide
CO2 in a Shrimp Tank

How Copper Affects Dwarf Shrimp
Shrimp Safe Plant Fertilizers
The point is that a high level of CO2 and Copper (most fertilizers contain copper) is extremely dangerous to the shrimp.

Care and Maintenance of Mermaid Weed

  • In aquariums, this plant is commonly used as a classic stem plant, planted in dense groups along the sides and as a mid orbackground plant due to its larger size.
  • Depending on the conditions, this plant has a slow to moderate growth rate. For example, you will have 1-2 inches in a month if you have poor lighting and no CO2.
  • Underwater, it demonstrates its best decorative qualities. Do not allow it to grow above the surface. Start trimming it when there are 4-6 (10-15 cm) inches to the surface of the water.
  • Under optimal conditions, it does not grow ugly aerial roots.

Planting Mermaid Weed

It is a pretty straightforward process. You simply need to plant it deep enough in the substrate to keep it from floating up. There is no special method or trick involved in the planting process itself.

Unlike some plants that can be left floating until their root system develops and they are ready to be planted in the substrate, it is not advisable to do so with Proserpinaca palustris.

Related article:

Propagation of Mermaid Weed

In its emersed forms, Proserpinaca palustris reproduces through seeds, which is most suitable for outdoor cultivation.

In aquariums (submersed form), we can propagate it from stem cuttings.

  • Take a healthy stem cutting, making sure it has several leaves and nodes.
  • Cut it between the nodes.
  • Remove any leaves from the lower portion of the cutting and plant it in the substrate.
When it comes to propagation, let’s just say it’s lackluster.

It only produces side shoots when trimmed, and even then, usually only 1 to 3 at a time. I’ve never seen more.

Besides, those side shoots also grow very slowly! While you get a handful, during that same period, you could easily cultivate several pounds (kilograms) of Hygrophila.

Problems Associated with Growing Mermaid Weed

Melting: Unfortunately, there are many reasons why this plant can melt all of the sudden.

  • Transition from an emersed form to a submersed form.
  • Sudden changes in water parameters can cause it to melt.
  • Too hard and/or alkaline pH.
  • Low lighting, overshadowing, and short photoperiod.
  • Not enough fertilization and CO2.

Discoloration: Proserpinaca palustris is one of those plants that, depending on environmental conditions, can display a wide range of colors, ranging from light green to red and even purple. Achieving a red hue is often impossible without optimal conditions. In low-tech aquariums, the primary color will be green with a slight yellowish tint.

Leggy bottom leaves: When Mermaid Weed gets really large (or reach the surface) the lower leaves may die back. Top leaves start blocking the light for the lower leaves.

Solution: Prune the plant. Check the lighting and provide CO2. These are usually the main reasons.

Ugly aerial roots: Mermaid Weed usually does not produce long aerial roots which are pretty ugly in my opinion. However, it can happen under suboptimal conditions and/or the plant grows emersed.

RelocationThe plant may melt after relocation or propagation by splitting even within the same tank. It does not like to be disturbed. Additionally, cutting roots will negatively affect it.

Solution: Do not have any. Just be careful and patient.

Nutrient sensitive: This plant cannot survive without nutrition for a long time. It dies down due to a lack of nutrients.
Solution: Regular feeding.

Algae: Due to its relatively slow growth, the plant is more susceptible to gets covered in algae.

Related article:

Benefits of Mermaid Weed

Aquascape:  The color, shape, and form of this plant will be an excellent decorative addition to any aquascape.

Mermaid Weed (Proserpinaca palustris) – Detailed Guide Care, Diet, and Breeding - pearlingOxygenation (pearls):  Proserpinaca palustris has a distinct feature which is the production of small pearls or bubbles of oxygen that stay on top of the plant, this adds a very lively aspect to the plant.

Prevents gas pockets: This plant has a well-developed root system that will help to break up anaerobic pockets in the substrate.
Note: Hydrogen sulfide pockets (H2S, the gas smells like rotten eggs) can be really dangerous to your fish or shrimp.

Hiding place: It will serve as an excellent cover and hiding place for inverts and small fish. They love to play in it and pick on it.

Foraging place: Acts as a buffet of biofilm, which is an ideal first food for newly hatched fry and shrimplets.

In Conclusion

Mermaid Weed is an impressive and captivating aquatic stem plant. Thanks to its distinctive shape and vibrant colors, it has the ability to create various artistic effects in aquascaping.

However, it comes with its own care challenges.

To achieve its desired classic look, this plant requires CO2, nutrient-rich substrate, regular fertilization, and strong lighting, all of which need to be perfectly balanced. It will struggle in a low-tech tank. Therefore, it is more suitable for experienced aquarists due to its high demands and specialized care.

References:

  1. McCallum, William Burnet. “On the nature of the stimulus causing the change of form and structure in Proserpinaca palustris.” Botanical Gazette34, no. 2 (1902): 93-108.
  2. de Wit, H. C. D. “Introduction to aquarium plants and some remarks on Proserpinaca palustris L.” The AquariumApril (1960): 103-108.
  3. Davis, Graham J. “Proserpinaca: photoperiodic and chemical differentiation of leaf development and flowering.” Plant Physiology42, no. 5 (1967): 667-668.
  4. Roskov Y., Kunze T., Orrell T., Abucay L., Paglinawan L., Culham A., Bailly N., Kirk P., Bourgoin T., Baillargeon G., Decock W., De Wever A., Didžiulis V. (ed) (2019). “Species 2000 & ITIS Catalogue of Life: 2019 Annual Checklist”. Species 2000: Naturalis, Leiden, the Netherlands. ISSN 2405-884X. TaxonID: 53479096. Retrieved 2019-11-11.

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