Water Soldier is an unusual-looking plant. One popular common name is in fact "pineapple plant" thanks to its leaf arrangement. Prior to the construction of the Marchfeldschutzdamm (the Marchfeld protective barrier), long beds of Water Soldier graced the backwaters in the swampy parts of the Marchfeld, farther from the Danube river. Today, this plant – which resembles a tropical Bromeliad – can only be found in certain backwaters (e.g. the Rosskopfarm) and in the March wetlands.
Description
Water Soldier is a perennial, funnel-shaped rosette plant which spends most of the year submerged underwater. Its stiff, saw-edged, sword-shaped rosette leaves are around 40cm long and 3cm wide. During flowering, half of their total length at most emerges from under the water. Like all members of the Alismataceae family, its flowers have three petals and are significantly larger than the greenish-coloured sepals. The plant is dioecious, and the male flowers have only stamens and the female flowers carpels. Stemless roots are formed on the underside of the rosette; these serve mostly to anchor the plant in the muddy bottom.
Distribution
Water Soldier may be found from Central Europe to western Siberia but is limited to lower elevations. In Northern and Southern Europe it is only rarely occurring. In Austria, Water Soldier may be found only in the March and Danube wetlands.
Endangerment and Conservation Status
Due to the rarity of suitable locations, Water Soldier is critically endangered in Austria. A problematic issue is that Water Soldier itself plays a major role in sedimentation of its own habitat. The species is dependent on the colonization of naturally-emerging backwaters and bends in the river which are cut off from the main river. When the development of such natural habitats is hindered by river regulation, Water Soldier disappears – along with a long list of other floating plants such as Common Frogbit (Hydrocharis morsus-ranae). On a local level, fishermen have also facilitated the disappearance of this species, as the thick bed of Water Soldier makes fishing impossible and is sometimes removed.
Ecological Characteristics
As bodies of water begin to warm up in spring and early summer, Water Soldier rises from its frost-resistant winter quarters on the bottom of the pond and floats to the surface, where portions of the rosette leaves become fully visible. From May to August, white flowers appear on the rosettes above water; however, due to insufficient presence of the other sex, successful reproduction rarely takes place. Flowers may in fact not be formed at all. If the plant is not satisfied with the existing conditions, it may remain submerged or only emerge for a short time. Vegetative reproduction takes place by way of offsets formed on secondary rosettes which remain tied to the parent plant for a considerable time. In waters with thick vegetation, rosettes may be stacked densely on top of each other and may thus expand to fill all available space. In the autumn, the outer leaves die off while the inner rosette portions gain in weight by accumulating calcium carbonate, which makes them heavy enough to sink back to the bottom of the pond.
Special Characteristics
A dioecious plant, it may sometimes occur that only male or only female individuals may be found in any one location. Thus propagation must take place by vegetative means, namely through stolons which form new rosettes at their termini. If an area has been flooded, a single offshoot rosette which drifts into suitable waters will be able to build a carpet of Water Soldier. Dispersal of vegetative rosettes is also possible thanks to birds transporting nesting material.