Saxifraga cernua L.
Nodding saxifrage, bulblet saxifrage.
Sp. Pl. 1: 403. 1753.
Saxifraga var. exilioides Polunin, Bull. Mus. Natl. 92: 254. 1940.
Saxifraga cernua subsp. exilioides (Simm.) Engl. & Irmsch. emend Porsild, Bull. Mus. Natl. 135: 135. 1955.
Saxifraga cernua forma latibracteata (Fern. and Weath.) Polunin, J. Bot. 74: 100. 1938.
Saxifraga cernua forma bulbillosa Engl. & Irmsch. in Engler, Das Pflanzenreich 67: 274. 1916.
Saxifraga cernua forma ramosa Geml., Flora Sibir. 6: 162. 1769.
Plants with erect unbranched stems arising close together, or with single unbranched stems; 10–25(–35) cm high; vegetatively proliferating by bulbils not in the inflorescence (in leaf axils near the base of the plant). Aerial stems erect; densely hairy. Leaves mostly basal; alternate; heterophyllous (upper flowering stem leaves reduced, often bract-like, linear, not lobed, 1.5–7 mm long 0.3–3.0 mm wide, sessile); deciduous. Petioles 10–50 mm long. Blades (3–)5–15(–20) cm long; 5–25(–35) mm wide; herbaceous, or succulent; circular (sometimes), or reniform; with palmate veins, or with inconspicuous veins; glabrous. Leaf bases cordate, or obtuse (broadly). Leaves lobed (5–7, rarely 3–9, rounded to acute lobes). Leaf margins with non-glandular hairs (sometimes sparse), or glabrous. Leaf apices rounded.
Flowering stems 4–25 cm long; with leaves (gradually reduced in size towards the inflorescence); hairy (with glandular hairs). Flowers solitary (sometimes absent), or in inflorescences. Inflorescence racemose; 0–2.5 cm long; with bulbils (in axils of reduced leaves below the flowers). Flowers per inflorescence (0–)2–5; medium-sized, 5–15 mm in diameter or length. Calyx sepals 5; green; hairy; hairs glandular (with glandular hairs). Petals white; obovate, or spatulate; unlobed; 5–12 mm long. Stamens 10. Carpels partly fused; 2. Gynoecia superior. Styles 2. Stigmas per style 1. Fruit with calyx persisting; brown; hairy.
Chromosome information. 2n = 36–73 (Löve and Löve 1975).
Distribution. Circumpolar. Arctic, or alpine. Common.
Ecology and habitat. Polunin (1940) noted that this species frequently flowers far into the summer, but has not been observed to set seed. It reproduces by means of numerous reddish bulbils produced in the axils of the flowering stem leaves and bracts.
Taxon as an environmental indicator. This is a morphologically very plastic taxon in which the habit of the plant and size of the leaves may indicate favourable or unfavourable environmental conditions. The northernmost record is Low Point, 83°06'N, on the north coast of Greenland. It has been collected in Canada from Ward Hunt Island, 83°05'N (CAN).
Notes. Described by Porsild (1957) as "nodding in youth". Field observations are that the nodding may occur before and after anthesis.
Polunin (1940), recognized taxa that we have not maintained. These were:
1. subsp. cernua, the usual one occurring throughout our area.
2. var. exiliodes Polunin. Plants occurring on the mainland regions of the Northwest Territories.
3. forma latibracteata (Fern. & Weath.) Polunin. This taxon had been initially recognized as a variety but Polunin noted that it once appeared to "have the geographical delimitation of a true variety, but is now seen to be a mere frondose phase developed almost everywhere (at least in our area) that the species grows in humid places among rocks". It had been distiguished on the characters: leaf blades larger, 10–55(-70) mm long, 8–20(-25) mm wide; 5–8 lobed.
4. forma bulbillosa Engler & Irmsch. "bulbillis nigris permultis dense instructis". Polunin (1940) described this as a forma crassa, which in our area has been collected on the west coast of Hudson Bay - in the case of Macoun's Fullerton material "on wet refuse from dog stalls" and on the closely adjacent Southampton Island. It forms a marked contrast to the slender and graceful var. exilioides of the same region.
5. forma ramosa. A rare form that Polunin (1940) considered to have been collected in the Arctic Archipelago.
Porsild (1957) and Hultén (1968) did not recognize any of the intraspecific taxa recognized by Polunin (1940). This species is plentiful everywhere, and one of the chief plants in the High Arctic. It has a very wide range of tolerance to most environmental conditions, occurring in almost all habitats from wet to very dry and sheltered to exposed, and doing especially well in manured areas and snow patches. It is highly resistant to frost. This taxon appears to be a phenotypically plastic one in which various expressions have been named.
Saxifraga cernua was one of seven arctic species studied at Truelove Inlet, Devon Island (Atkin et. al 1993) for their ability to utilize nitrate nitrogen under field conditions. Saxifraga cernua, S. oppositifolia, Ceratium alpinum, Oxyria dygyna, and Papaver radicatum were able to use nitrate nitrogen, while Dryas integrifolia and Salix arctica showed little utilization. Porsild (1957, 1964) and Porsild and Cody (1980) recognized a single taxon for this species and did not accept any of the four intraspecific taxa recognized by Polunin (1940). No reason to do so has been found.
Illustrations. • Plant habitat in gravel. Plants growing in moist gravel with single terminal white flowers and numerous red bulblets up the flowering stems. These detach and may develop into new plants. L.J. Gillespie, s.n. • Plant habitat in moss. Plants growing in a thick cover of moss. Terminal flowers, usually with 5 white petals are borne erect. CMN Photo-Library. • Close-up of plants. Plants with a single, erect, terminal flower growing in wet calcareous gravel and moss. Nunavut, Cornwallis Island, Resolute Bay, west side of Satellite Hill Road, 74°40'N, 94°50'W. S.G. Aiken 98–056. CAN. Scale bar in cm. Photograph by Mollie MacCormac. • Line drawing of plant. Base of plants showing fibrous roots, bulb leaves from which leaves with long petioles develop, and the deeply crenate leaf blades. Plants in the high Arctic rarely have long petioles. • Inflorescence and bulblets. Flowering stem with a single terminal flower and red bulblets (arrow) growing in the axils of bracts. Bulblets fall off and can vegetatively propagate new plants. CMN Photo-Library. • Close-up of flower. Terminal soliatry flower, with 5 white petals,10 anthers and two carpels topped with white pom-pom stigmas. Flowering stem with red vegetative bulbils. Nunavut, Cornwallis Island, Resolute Bay, west side of Satellite Hill Road, 74°40'N, 94°50'W. S.G. Aiken 98–056. CAN. Scale bar in cm. Photograph by Mollie MacCormac. • Close-up of flower. Flower with probably only 5 white petals, and 10 anthers,(not all of which are visible). These are borne on a reddish recepatacle that is semi-inferior. There are two carpels topped with pom-pom stigmas. CMN Photo-library. • ‘Nodding’ inflorescence stem and leaf close-up. Flowering stem ‘nodding’, from the weight of a developing fruit. This is the origin of its common name, 'Nodding Saxifrage'. Nunavut, Cornwallis Island, Resolute Bay. Note that on the same plant there are 3- and 5-lobed leaves. • Nodding inflorescence. Flowering stem 'nodding' from the weight of a terminal fruit. Both covered with glandular hairs. Nunavut, Ellesmere Island, Scoresby Bay, 79°53'N, 71°33'W. S.G. Aiken 98–035. CAN. Photograph by Mollie MacCormac. • Arctic Island Distribution.
Cite this publication as: ‘C.L. McJannet, S.G. Aiken, M.J. Dallwitz, L.J. Gillespie and L.L. Consaul. 1997 onwards. Saxifragaceae of the Canadian Arctic Archipelago: Descriptions, Illustrations, Identification, and Information Retrieval. Version: 28th November 2000. http://www.mun.ca/biology/delta/arcticf/’. Dallwitz (1980), Dallwitz, Paine and Zurcher (1993, 1995, 2000), Aiken, Dallwitz et al. (1999), and Aiken, Dallwitz, McJannet, Gillespie, and Consaul (1998) should also be cited (see References).
