Arrowhead is a plant of many forms and has adapted ideally to the ever-changing conditions found in wetlands habitats. In deep waters, it forms narrow, ribbon-like leaves below the surface. Above water, it has floating oval leaves. The typical arrowhead-shaped aerial leaves are only formed when water levels are low. On very sunny sites, these leaves are arranged on a north-south axis, the Arrowhead functioning as a so-called compass plant.
Description
Arrowhead grows from 20 to 200cm tall and, depending on water levels, can take many forms. The submerged leaves arranged rosette-like are initially ribbon shaped, but floating oval leaves take form once the water surface has been reached. The typical arrowhead-shaped aerial leaves only grow when water levels are low or if the site is extremely dry. Flowering takes place from June to August. The flower stalk is triangular and monoecious; flowers are arranged in whorls. The lower part of the inflorescence contains the pure white flowers; female flowers have longer stalks than the male flowers. The three-petalled flowers are circle-shaped with a diameter from 10 to 15mm and have a noticeable dark purple centre.
Distribution
This species prefers warmth and is only found up to elevations of 500 to 600m but across Europe and western Asia, all the way to Lake Baikal. In Austria, Arrowhead may be found along major rivers such as the Danube, March and the Mur, and may also be spotted on Lake Constance; thus it is found in Burgenland, Vienna, Lower and Upper Austria, Styria, Carinthia and Vorarlberg. Arrowhead inhabits shallow, slow-moving waters and wet soils. In the Donau-Auen National Park, Arrowhead may be found on the margins of waters on the north bank, often in great numbers.
Endangerment and Conservation Status
As a semi-aquatic plant highly adapted to extreme fluctuations in water levels, the Arrowhead is classified as endangered: its suitable habitats are being eliminated by river regulation and the construction of power plants. The species enjoys protection under The Vienna Environmental Protection Act.
Ecological Characteristics
This species tolerates extreme fluctuations in water levels and adapts the form of its leaves to the prevailing circumstances. In deeper waters however, the Arrowhead does not flower. Towards the end of the vegetation period, the parent plant sends out runners which form starchy tubers. In the spring, new growth emerges from these tubers. If there are no major fluctuations in water levels, Arrowhead has difficulty competing with other flora and is normally edged out by other, more robust marshy plants.
Special Characteristics
The starchy tubers of the Arrowhead used to be consumed widely. Fresh, cooked tubers are said to taste slightly nut-like or a bit like peas. Arrowhead is highly recommended for planting in garden ponds at low elevations and can be purchased at well-stocked garden specialists. Unfortunately, some dealers often sell non-native species such as the North American Sagittaria latifolia. Demand the native Sagittaria sagittifolia and make a significant contribution to the preservation of an endangered species!