The flora of the Audomarois marsh

The Yellow Water Lily – Walk in Audomarois and the Pays de Saint-Omer

3 Flora of the Audomarois marshes: plants of the banks and wetlandssome

The edges of the watercourses and wet ditches of the Audomarois marsh are full of plants which adapt to variations in humidity and often play a decorative role while being essential to the ecosystem.

Meadowsweet

Meadowsweet (family Rosaceae) is a plant of wetlands, highly valued not only for its beauty but also for its medicinal properties. Indeed, this plant contains salicylic acid, a precursor to aspirin, which gives it pain-relieving properties. Its delicate flowers and vigorous growth make it a symbol of renewal in wet meadows.

Flowering rush or umbel-shaped rush

Flowering rush , also known as flowering rush (family Butomaceae), can reach up to one meter in height. It grows along the banks of waterways, particularly in shallow, slow-moving waters. Thanks to its elegant appearance, it is often used in landscaping. As a protected species, it highlights the importance of conserving these habitats to preserve biodiversity.

Hairy willow herb or large-flowered willow herb

Typical of waterways and damp ditches, hairy willowherb ( Epilobium hirsuta , family Onagraceae) is distinguished by its large pink flowers and serrated leaves. The hairs that adorn its stems give it a slightly "hairy" appearance, hence its name. Its abundant flowering adds a touch of bright color to marsh landscapes.

Yellow Pigamon

The Yellow Meadow-rue (family Ranunculaceae) is an imposing plant that can reach about one meter in height. Its densely clustered, yellowish flowers brighten meadows and riverbanks. Found in ditches and along canals, this protected species symbolizes the fragility and beauty of wetlands.

Phragmites (reed)

The common reed (Phragmites ), a herbaceous plant of wetlands, is distinguished by its long, sturdy stems and narrow leaves. It grows mainly in marshes and along pond banks, contributing to soil stability and promoting biodiversity. This species is essential for the balance of natural aquatic ecosystems. Immense and majestic, these reeds structure the banks and provide a suitable habitat for numerous species of birds and invertebrates. It holds a prominent place in the flora of the Audomarois marsh, as it is frequently found along the edges of drainage ditches.

Water aloe

In the Audomarois marsh, the water aloe impresses with its fleshy, green and ribbed leaves, as well as its robust and branched stems. Adapted to humid environments, this exotic plant offers a valuable habitat, contributing to biodiversity and bringing a touch of freshness to the marshy landscape for a natural balance.

4. Trees and large terrestrial plants of the Audomarois marsh

Beyond aquatic plants and wetlands, the Audomarois marsh is also dotted with trees and terrestrial plants which structure the ecosystem and offer varied habitats.

Pollarded willows

Pollarded willows are remarkable trees due to their distinctive morphology. Their rounded, globular shape results from a healing process of the branches. The top of the trunk hollows out, forming a cavity that fills with rich organic matter from the decomposition of leaves, wood, and even insect excrement. These cavities create an ideal environment for the germination of seeds dispersed by the wind or birds, thus encouraging the growth of other grasses and shrubs such as nettles, brambles, hawthorn, currants, elderberries, and so on. It's important to note that the term "pollarded" has nothing to do with any particular species of willow. It simply refers to a white willow that is pollarded every six years. When the branches regrow, they form a green ball reminiscent of a baby frog or toad. This is undoubtedly a symbolic tree for the Audomarois marsh.

Hemp-leaved Joe Pye Weed

Hemp -agrimony (family Asteraceae) is distinguished by its leaves divided into 5 to 7 leaflets, strangely reminiscent of hemp leaves. Its aerial structure and its ability to grow in damp environments make it a valuable indicator of soil and water quality.

The neglected orchid

The Neglected Orchid (Orchidaceae family) is a rare gem of the wet meadows of the Audomarois marsh. This plant displays lip speckled with tiny purple dots, giving it a discreet yet undeniable charm. Its limited presence in the northern third of France and its protected status make it a species of exceptional interest to naturalists and nature lovers.

The walnut tree, sentinel of the banks

The walnut tree is an emblematic tree of the Audomarois marshland, often found along riverbanks. Traditionally, it served as a parasol to protect wooden boats from the sun's rays. Indeed, boat planks are not stabilized. As they dry, they risk developing gaps, and therefore leaks. Hence the importance of this tree in the past.

Other common trees appearing among the flora of the Audomarois marsh

The Audomarois marsh includes a multitude of tree species:

• Hazel: This common tree, whose hazelnuts feed many animals, fits perfectly into the plant fabric of the marsh.

• Poplar: A fast-growing tree, often planted along rivers to provide shade and protection from the wind, has a life expectancy of around forty years. Attempts are now being made to remove it from landscapes. In fact, planted near river banks, it creates a fairly high risk of windfall because its root support is not complete. Its anchoring is therefore insufficient, which is not the case for ash and willow, for example.

• Linden: A shade tree par excellence, it embellishes the edges of the marsh with its dense foliage and soothing flowers.

• Beeches: These trees, although more characteristic of forest environments, sometimes adorn the edges of the marsh, providing shade and structure.

• Ash: In the Audomarois marsh, the ash tree stands out for its robustness and dense branching. Adapted to humid soils, it offers a rich habitat for fauna and flora.

• white willow : In the Audomarois marsh, the white willow spreads its long, flexible branches and elegant twigs. Adapted to wet soils, it contributes to the ecological balance by providing refuge to wildlife and stabilizing the banks.

• Weeping willow : In the Audomarois marsh, the weeping willow stands out with its long, drooping branches and elegant silhouette. Adapted to wet soils, it stabilizes the banks while providing shelter to a variety of wildlife. This emblematic tree embodies the gentleness and melancholy of a soothing natural landscape with changing colors.

5. Flora of the Audomarois marsh: plants on the edge and in intermediate environments

The edges of the marsh are teeming with a diversity of species which, even if they do not live directly in the water, play a crucial role in the structuring and dynamics of wetlands.

The bushes

Wild elderberry : A shrub typical of wetlands, whose black berries and white flowers bring softness and color to the landscape. They are often found along riverbanks.

Blackberries : These brambles produce tasty fruit and attract a variety of wildlife, contributing to seed dispersal. Similarly, they are often found in abundance on certain riverbanks.

The banks of the marsh sometimes contain beautiful patches of blackberries – A walk in the Audomarois and Saint-Omer region

Irises and other typical marsh plants

• Yellow Iris (Yellow Iris or Marsh Iris) : This plant, with its bright hues, thrives on water's edges, bringing a colorful touch to the humid landscape.

• Sweet flag : Often confused with the iris, this aromatic shrub gives off a pleasant scent that charms both walkers and pollinating insects.

• High Agrimony : Herbaceous plant that adapts to humid soils, its small delicate flowers bring lightness and texture to meadows.

• Ribwort water-plantain : As its name suggests, it likes water and is distinguished by its lanceolate leaves, which give it a slender and graceful appearance.
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 The water iris – Walk in Audomarois and in the Pays de Saint-Omer

Other elements of the flora of the Audomarois marsh

It is impossible to list the hundreds of species of plants that make up the flora of the Audomarois marsh. Here is a short list of the best-known plants:

• Sedge : A discreet plant in the aquatic environment, it contributes to the stability of the banks and to the natural filtration of the water.
• Water hemlock : Although toxic, this plant occupies an important ecological place as an indicator of water conditions.
• Hawthorn : A thorny shrub, appreciated for its white flowers and red berries, it offers a refuge to wildlife.
• Marsh horsetail : Primitive plant with hollow stems, it is found in very humid areas and helps maintain biodiversity.
• False bindweed : A creeping plant that creeps along river banks, contributing to vegetation cover and preventing erosion.
• Lier : A climbing species par excellence, it clings to trees and walls, providing a habitat for numerous insects.
• Wort : Plant with bright yellow flowers, used for a long time in herbal medicine, it colors meadows and wastelands.
• Purple Loosestrife : A typical plant of wetlands, it is distinguished by its small flowers and its ability to grow in marshy land.

• Wild lettuce : Witness to the richness of wet meadows, this plant brings a touch of freshness to the banks.
• Wild Mallow : With its delicate, pale pink flowers, it contributes to the colorful palette of the marsh.
• water mint : With an invigorating fragrance, this plant thrives in humid areas and provides a popular aromatic note.
• Marsh forget-me-not : Small and discreet, the forget-me-not embellishes the banks with a soft blue and recalls the sweetness of humid springs.
• Watercress (or watercress): A tasty and crunchy plant, it grows in running water and participates in the food cycles of wildlife.
• buttercup : Known for its delicate yellow flowers, it brightens up clearings and pathsides.
• Marsh vetch
• Sorrel : An edible plant, sorrel thrives in nutrient-rich soils and brings a tangy note to marsh gardens.
• briar : This wild rose bush, with fragrant flowers, is emblematic of the countryside and contributes to the preservation of traditional know-how.
• Nettle : Although it is often feared for its stinging hairs, the nettle is an ecological ally, nourishing the soil and promoting biodiversity. In the Audomarois marsh, in the local dialect, they are nicknamed "piquinettes".

Common bladderwort: the carnivorous plant of the marsh

Common bladderwort, or Utricularia vulgaris, is a fascinating carnivorous plant that populates the Audomarois marsh. This aquatic species is distinguished by its small vesicles, called utricles, which discreetly capture tiny invertebrates and sometimes even small fish. Adapted to wetlands, it contributes to the balance of the ecosystem by regulating the population of its prey. Its presence enriches local biodiversity and intrigues researchers and botany enthusiasts. Discreet but effective, Utricularia vulgaris embodies the ingenuity of nature in the adaptation and innovation of its nutritional mechanisms.

6. A fungal and cryptogamic heritage

Although the flora of the Audomarois marsh is mainly associated with vascular plants, the wealth of fungi, bryophytes and lichens should not be overlooked.

The mushrooms

In 1996, an inventory carried out in the marsh identified 91 species of fungi . Fourteen of these species are on the Regional Red List, highlighting the importance of preserving these microorganisms which play an essential role in the cycle of organic matter and soil fertility.

Mosses and lichens

The wetlands of the marsh also support the growth of nearly 20 lichens and 13 moss species . These often inconspicuous organisms are sensitive indicators of air and environmental quality. Their presence contributes to the complexity and resilience of the ecosystem, providing essential microhabitats for numerous insects.

7: Flora of the Audomarois marsh and invasive species

In the Audomarois marsh, two invasive plants are disrupting the natural balance: the Jussie and the Brazilian Milfoil. The Jussie, native to America, is spreading rapidly along the banks thanks to its vigorous growth and its ability to colonize aquatic environments. This compact plant competes with local species by limiting light penetration and changing habitat conditions. At the same time, the Brazilian Milfoil, characterized by its finely cut leaves, is invading the calm waters of the marsh. Its accelerated proliferation is altering the composition of the vegetation, causing ecological imbalances and disturbances for wildlife. Managing these invasive species is crucial to preserving the biodiversity of the Audomarois marsh. Targeted actions are underway.

8. A heritage to preserve for the future

The Audomarois marsh is not only a place of natural beauty, it is also a living witness to the history and biological wealth of the Nord-Pas-de-Calais region. International recognition, with its integration into the global network of MAB biosphere reserves, underlines its importance for global biodiversity. However, despite this precious heritage, the marsh flora is under significant pressure. The degradation of water quality, urbanization and changes in agricultural practices contribute to the decline of certain species.

The biodiversity of the Audomarois marsh is a natural gift that is both precious and fragile. It invites us to rethink our relationship with nature, to consider it not only as a reservoir of resources, but above all as a living heritage that it is our responsibility to protect. By promoting respectful management practices and supporting ecological monitoring research, we can hope to restore these environments to their former dynamism and guarantee the survival of these emblematic species for future generations.