Provisional distribution and habitat texts for Sagittaria
(by Christopher D. Preston, for Flora Nordica 12)
S. sagittifolia map

Distribution. D most frequent on the west side of SJy and southern VJy, occasional in ØJy and rare elsewhere. Need information on current status. S rather local in the south, north to Dlr and Gst, though frequent along suitable rivers and lake shores, perhaps more frequent in Srm than elsewhere; extending in a few additional localities north to Jmt Håsjö and Ång Nora and Skog. F frequent in parts of the south, especially U, EK, St and EH, otherwise with a rather patchy distribution inland in southern Finland, usually in areas of base-enriched waters; western in the middle latitudes, extending north along the Bothnian coast and the rivers draining down to it to PeP one square mapped by Suominen (1986) – where?

Habitat. Found at the edge of lakes, streams and rivers, and in ponds and pools, usually in eutrophic water bodies or in places which there has been some nutrient-enrichment. It is often found in sheltered sites where it is rooted in soft, clayey or silty substrates but will grow in sandy and gravelly places. Its optimum depth is perhaps 0.2-0.5 m, but plants will sometimes flower at depths of at least 1.2 m. However, in deeper water plants often have only submerged leaves, and such material has been collected at depths of at least 2 m.

S. natans x sagittifolia map

Distribution. S extends further south in Sweden than S. natans though rare towards the southerly edge of its range; also rare in the westerly provinces but increasing in frequency in the easterly provinces from Hls northwards to Nb. F well established in some lake and river systems in the absence of one or locally of both parents; also apparently absent from some systems in which both parents occur. Formerly known from EK Kymi, Mussalo (last collected 1936), known from one area of St Noormarkku & Pori, well-established in the Päjänne system in EH and southern PH, and in add name for lake area in PS, and widespread in the river systems of Kn, OP and PeP. Also recorded from a few localities in the Lapland provinces, northwards to InL mapped by Suominen (1986), where?

Habitat. This hybrid usually grows in water 0.5-1 m deep, although in places at depths as shallow as 10 cm, at the edges of lakes, in sheltered bays by rivers or by the main channel of slow-flowing rivers, and in ponds in former river beds. At the northern end of the Gulf of Bothnia it grows in shallow water in sheltered bays, as well as coastal pools (sometimes with intermittent connection to the sea) and at the mouth of rivers. It is recorded from a range of waters from oligotrophic to eutrophic, and in slightly brackish conditions at its coastal sites, and over a range of substrates including fine sand and mud.

Sagittaria natans map

Distribution. S rare at coastal sites in Mpd, Ång and Vb, and inland in Jmt Berg, more frequent in Nb comment on range here and with a single known site at TL Vittangi, Lake Vivunkijäru. F absent from the south-west, patchily distributed in middle latitudes with concentrations in the lake and river systems of eastern St, PS and northern ES, PK, southern Kn, and perhaps more frequent in OP and PeP but very rare in Lapland, with the northernmost confirmed record at  where?

Habitat. A plant of lakes, slowly flowing rivers and the ponds marking the former course of rivers, at a range of nutrient levels from oligotrophic to moderately eutrophic. Its optimum depth is greater than that of S. sagittifolia, with populations flowering at depths of 0.5 to 1.5 or even 2 metres. It is found over a range of substrates including soft sediments (including clay and silt), fine sand  and pebbles. 

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This page was updated 2007-07-27