Water Aloe - Stratiotes aloides: Planting and Cultivating

Botany and Description

The water aloe, also known by its scientific name Stratiotes aloides and commonly referred to as water soldier, aquatic aloe, or water pineapple, is an aquatic plant belonging to the Hydrocharitaceae family (Hydrocharitaceae). The genus name, Stratiotes, originates from the ancient Greek “stratiotēs”, meaning soldier, in reference to its robust, sword-shaped leaves that resemble natural armour.

In its natural habitat, this plant is typical of stagnant or slow-moving waters, such as ponds, ditches, lakes, and marshes. It thrives particularly well in fresh water rich in nutrients, while requiring good light to fully develop. Native to Europe and Asia, Stratiotes aloides is predominantly found in Northern and Central Europe, from the Netherlands to Scandinavia, through Germany and the United Kingdom. Its range extends to Russia and Western Siberia. However, in some regions, this plant has become rare, notably due to pollution and habitat destruction. Due to the regression of natural wetland habitats, it is a protected plant in France.

Foliage and flowering of Stratiotes aloides. On the right, botanical illustration (circa 1903).

The water aloe is a perennial aquatic that forms beautiful floating rosettes on the surface, reminiscent of those of terrestrial aloes. These compact and elegant rosettes can measure between 20 and 50 centimeters in diameter, with rigid and sharp leaves. Their lance-shaped form, combined with finely dentate edges, gives them a unique and functional appearance. These leaves, which can grow up to 60 centimeters long, display shades from light green to dark green, sometimes punctuated with reddish hues as they age. In addition to their beauty, the leaves play a crucial ecological role by oxygenating the water and limiting algae growth by shading the water surface.

The root system of this plant is primarily floating, with roots that extend into the water to capture dissolved nutrients. Although it can occasionally anchor temporarily in the sediments, it remains predominantly a floating species. This characteristic allows it to adapt to variations in depth and light in its aquatic environment.

In spring and summer, the water aloe is distinguished by its delicate flowering, which typically occurs between May and July. The flowers, borne at the water’s surface, are unisexual and illustrate the dioecious nature of the plant, with distinct male and female individuals. The white flowers, with a pale yellow heart, measure about three to four centimeters in diameter. The male flowers, slightly larger and more spectacular, contribute to pollination, a process that occurs through water, thanks to an adaptation called hydrophily (pollen is transported by water).

Flowering of Stratiotes aloides

Fruiting of the water aloe remains a rare event, especially outside its natural habitat. When it occurs, it produces small ovoid fruits filled with seeds, maturing underwater. However, this plant primarily reproduces vegetatively, through its stolons, creeping lateral stems that allow rapid colonization of favorable aquatic areas.

The water aloe plays an important ecological role in its ecosystem. It provides valuable shelter and breeding areas for numerous aquatic species, from fish to insects. In winter, this plant adopts a remarkable survival strategy: it sinks into the depths of the water bodies to escape freezing, resurfacing with the return of warmer weather thanks to its air-filled tissues.

Moreover, this plant is not only useful in its natural habitat. In artificial ponds, it is highly valued for its aesthetics and its ability to purify water by absorbing excess nutrients. It is also used in phytoremediation programs to combat eutrophication**. However, its excessive proliferation, possible in nutrient-rich waters, can sometimes become problematic, requiring reasoned management.

*Phytoremediation is an ecological technique that uses plants to decontaminate soils, water, or air by absorbing, degrading, or immobilizing contaminants.

**Eutrophication is an ecological imbalance phenomenon in aquatic environments, caused by an excess of nutrients (notably nitrates and phosphates), leading to algae proliferation and a decrease in available oxygen, which threatens fauna and flora.

Our Favourite Varieties

Stratiotes aloides

Stratiotes aloides is a perennial aquatic plant forming a dense rosette of stiff, prickly leaves, which rises to the water surface during its flowering period. Perfectly hardy and prolific, it is valued for its water-purifying and oxygenating qualities in calm waters.

• Flowering time June to August
• Height at maturity 40 cm

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Planting a Water Aloe

Where to Plant?

The water aloe should be placed in a calm body of water, such as a pond or a lake. It prefers:

• A sunny area or slightly shaded.
• A water depth between 30 and 100 cm. Below or above this, the plant may struggle to adapt.
• A nutrient-rich substrate to encourage its growth if you want to anchor it.
• It does not like very high temperatures so avoid placing it in waters where the temperature can exceed 22°C.

A Note on the Substrate

If you wish to plant in a basket, opt for a substrate specifically designed, generally made up of a mix of clay, sand, and decomposed organic materials. This type of substrate is heavy enough to stabilize the plant and prevent it from floating or dispersing in the water.

To complement, it is advisable to add a layer of gravel or coarse sand, about two to three centimeters thick, on top of the substrate. This helps to keep the substrate in place while preventing nutrients from escaping into the water.

Finally, be sure to avoid using fresh organic materials, such as undecomposed compost. These elements could enrich the water with an excess of nutrients and promote eutrophication, an ecological imbalance harmful to the pond.

When to Plant?

The best time to “plant” the water aloe is in the spring (April) or late summer (September), when temperatures are still mild or the water begins to warm up. This allows the plant to establish itself before winter.

How to Plant?

• • Recommended! : for a floating plantation, simply place the water aloe rosettes on the surface. They will naturally adapt and their roots will float in the water. The mud at the bottom of the pond should be slightly acidic clay.
  • For an anchored plantation: secure the plant in a basket with aquatic substrate and place it at the recommended depth at the bottom of the pond. Unfortunately, this solution goes against the biology of the plant. Prefer the first solution, much more natural!
    

Caring for Water Aloe

Maintaining the Stratiotes aloides is relatively simple, as this aquatic plant is robust and self-sufficient under suitable conditions. Here are the main aspects to consider for its care and to maintain its balance in a pond or lake:

Monitoring Growth

Water soldier spreads quickly through its stolons. In a small pond, it can become invasive. To prevent overpopulation:

• Regularly remove excess rosettes, especially in summer, when the plant is in full growth.
• Divide the clumps if they become too dense, which also helps to renew the population and encourage healthy growth.

Removing Dead Leaves

Over time, some leaves may yellow or decompose:

• Remove them by hand to prevent them from degrading in the water and contributing to the build-up of organic matter, which could promote eutrophication.

Natural Overwintering

Water soldier adopts a natural strategy for winter:

• As the cold arrives, it sinks to the depths of the pond, where it remains in dormancy, protected from freezing. No special care is needed during this period.
• In spring, the plant will rise to the surface to resume its growth cycle.

Managing Light and Nutrients

Water soldier needs light to develop properly:

• Ensure the pond is not completely covered by other floating plants, such as duckweed, which could suffocate it.
• Maintain a nutrient balance in the water. If the water becomes too rich, reduce the input of organic matter (such as leaves or plant debris) or add other aquatic plants to consume the excess nutrients.

In some countries, the plant has become invasive

Potential Diseases and Pests

Possible Diseases

• Filamentous Algae
  Algae can proliferate in nutrient-rich water, covering the leaves of the water aloe and limiting the available light. Although not a disease per se, smothering by algae can weaken the plant.
  • Prevention: maintain a good nutrient balance in the water and introduce other aquatic plants to limit the excess.
• Leaf Rot
  In poorly oxygenated or stagnant water, leaves can begin to rot, especially if they are covered with organic debris. This can affect the overall health of the plant.
  • Prevention: regularly remove dead or damaged leaves to prevent their decomposition.

Potential Pests

• Aquatic Aphids (including Rhopalosiphum nymphaeae and similar species)
  These small sap-sucking insects can infest the emerged leaves of the water aloe, causing weakening of the plant.
  • Treatment: rinse the infested leaves with fresh water or allow natural predators such as ladybirds to intervene.
• Aquatic Beetle Larvae
  Some aquatic insect larvae can nibble on the leaves or roots of the water aloe, causing minor damage.
  • Natural Solution: introduce fish that feed on these larvae, such as mosquitofish or carp.
• Aquatic Snails
  Some snails, although useful for cleaning ponds, can sometimes chew on the leaves of the water aloe, especially if there are no other food sources.
  • Prevention: monitor the snail population and remove the excess if necessary.

All these “pests” are clearly not in the case of water aloe, so do not be too worried and let nature take its course. In 95% of cases, nothing will happen.

Propagating Aquatic Aloe

Water Aloe primarily (and easily!) propagates through vegetative division. The formation of seeds is very rare.

Propagation by Division of Rosettes

Water Aloe can naturally multiply through its stolons. The creeping stems that form around the main plant will give rise to new rosettes without human intervention. If you want to encourage this natural multiplication, ensure that the stolons remain in good contact with the water. They will eventually develop roots and produce new rosettes that can be separated once they are sufficiently developed.

• When to divide?
  The best time to carry out this division is in spring or early summer, when the plant is in full growth. This allows the new rosettes to establish well before the arrival of winter.
• How to divide?
  1. Remove the mother plant from the water gently to access the rosettes formed around the main plant.
  2. Separate the rosettes: each rosette is attached to the plant by a stolon (a creeping stem). Use your hands or a clean, sharp knife to cut the stolons and separate the rosettes.
  3. Replant the rosettes: the separated rosettes can be directly returned to float on the surface of the pond or fixed in a light aquatic substrate if you prefer to anchor them.

Care for the New Plants

The new rosettes, whether divided or naturally formed, require the same conditions as the mother plant:

• Water rich in nutrients, without excess.
• Good sunlight and a calm pond environment.

How to Successfully Pair Water Aloe with Other Aquatic Plants?

With its elegant silhouette and floating habit, the water aloe can perfectly integrate with a wide variety of aquatic plants, whether they are floating, submerged, or marginal.

For visual and ecological balance, it is wise to combine water aloe with plants that occupy different levels of the pond. On the surface, it can be paired with light floating plants like water lilies (Nymphaea), which provide large round leaves and colourful flowers that contrast with the clean rosettes of the water aloe. Other floating plants, such as frogbit (Hydrocharis morsus-ranae), can also be used, but sparingly to avoid blocking the light needed by the water aloe.

In the submerged zones, oxygenating plants such as spiked water-milfoil (Myriophyllum spicatum) or aquatic buttercup (Ranunculus aquatilis) perfectly complement the water aloe. These plants help maintain clear and well-oxygenated water.

The marginal zones, where water meets the banks, offer another level of association. Plants like water iris (Iris pseudacorus), cattails (Typha latifolia) or marsh horsetail (Equisetum fluviatile) bring verticality and texture that contrast with the floating habit of the water aloe. These marginal plants are ideal for filtering water by capturing excess nutrients and thus limiting the risks of eutrophication.

Finally, to enhance the aesthetic interest while preserving the balance of the pond, it is important to ensure that none of the associated plants dominate the medium. The water aloe, although robust, can be outcompeted by overly prolific species. Regular management, consisting of limiting the proliferation of floating plants or thinning out clumps of marginal plants, will help maintain a harmonious space where each plant finds its place.

Around Stratiotes aloides, water iris, cattails, aquatic buttercups, water lilies, and marsh horsetail.