A picture guide to aquatic plants of Zambian rivers (With preliminary allocation of trophic indicator scores) Osmunda regalis fringing a bedrock stream Michael Kennedy University of Aberdeen, Aberdeen AB24 2TZ, Scotland, UK. Kevin Murphy University of Glasgow, Glasgow, G12 8QQ, Scotland, UK. (May 2012) African, Caribbean and Pacific (ACP) group of States Secretariat: Science & Technology Programme Aims of the guide: The aim of this guide is to provide a simple first step in the identification of some common (and a few less- common) aquatic plants found within the streams and rivers of Zambia. Pictures and line drawings are provided which attempt to show the general habit of the plants, along with various diagnostic features. Concise plant descriptions and habitat descriptions are also provided. The guide is not intended to be definitive, but more of an aid to initial identification of plant species; where additional identification guides and diagnostic keys are available to the user (which may provide detailed descriptions, but also require the use of hand lenses and microscopes for example), these should be used in conjunction. Where users have internet, online resources such as the Flora Zambesiaca based at Kew Royal Botanic Gardens in the UK are helpful: http://www.kew.org/science-research-data/directory/projects/FloraZambesiaca.htm). Herbaria are also present in the Department of Biological Sciences at the University of Zambia (UNZA), and in Kitwe, associated with the Forestry College. Photographs were taken by the authors and colleagues; some line drawings have been adapted from Cook (2004). The guide is ordered into plant families, which often share major diagnostic features in common (e.g. ligules on leaf blades in grasses (Poaceae)), and then into genera and species. A short glossary is provided at the end of the species descriptions. The guide also provides provisional Trophic Ranks for several of the species*. The trophic ranks have been developed under the Southern African Freshwater Research Assessment (SAFRASS) project. Several countries already use aquatic plants to help indicate long term water quality (along with macroinvertebrates, diatoms). For each species description a coloured box containing a number is provided in the upper right-hand corner. These represent one of five general categories of river water nutrient (trophic) level that each species is associated with (some species are intermediate). Numbers with an asterisk (*) are based on very limited data, or information from non-Zambian trophic ranking schemes. 1 Plants are generally associated with very low nutrient conditions (Ultra-oligotrophic); 2 Plants are generally associated with low nutrient conditions (Oligotrophic); 3 Plants are generally associated with intermediate nutrient conditions (Mesotrophic) or are found across all nutrient conditions; 4 Plants are generally associated with moderately high nutrient conditions (Eutrophic); 5 Plants are generally associated with (or can tolerate) high nutrient conditions (Hypereutrophic); * The information provided represents the first stage in the development of a methodology to define trophic status of rivers in Zambia using aquatic plants; also to develop a method to use aquatic plants in monitoring water quality and potential change (Biomonitoring). The distribution of many aquatic plant species in Zambia is still not well known, whilst complete descriptions, guides and keys for many species are still in development; in addition long-term water quality datasets are not available for many rivers. The ranks assigned may therefore be based on only a relatively few samples, and as more information is gained then Trophic Ranks may have to be modified to represent new information and greater understanding of the species. Sample locations named are mainly from the Kasanka/ South Bangweulu area of Northern Zambia. This work was carried out with funding provided under the African, Caribbean and Pacific (ACP) group of States Secretariat: Science & Technology Programme. Family: Alismataceae Limnophyton angolense Lam. 2* Emergent, rooted. Leaf petioles (8-85 cm), leaf blades arrowshaped, 10-15cm (along midrib). Inflorescence 4-6 whorls of flowers, with 15 or more flower in each. 1 Rooted, Usually annual. Mainly submerged leaves, flowers and some leaves emergent. Leaves 11-34 cm long, 0.3-1.5 cm wide. Petiole and blade differentiated by a curved ‘hinge’. Inflorescence <10 cm with flowers in whorls Habitat: Slow-flowing waters, temporary flooded areas and wetlands. Family: Amaranthaceae Alternanthera sessilis Family: Alismataceae Wiesneria schweinfurthii J.D. Hooker Habitat: Permanent deep or slow-flowing waters, temporary pools and wetlands. 3 Family: Amaryllidaceae Crinum macowanii Baker 3.5 a, inflorescence (1 cm) b, bulb and leaves (15 cm) Annual or perennial, stems prostrate. Leaves, sessile, in opposite pairs, lanceolate to oval; 1-9 cm long, 0.2-2 cm wide. Flowers within white papery bracts Habitat: Terrestrial but common at river and pool edges, or floating in temporary flooded areas. Perennial, from a bulb. Fragrant white flowers with pink stripes and black anthers. Flowers conspicuous in the early rainy season. Habitat: damp grassland and dambos, and in seasonally (shallowly) flooded grassy areas alongside streams. Family: Aponogetonaceae Aponogeton desertorum Zeyher ex A. Sprengel 3 Family: Aponogetonaceae Aponogeton junceus Lehmann ex Schlecht 3* Perennial, leaves in basal rosette. Floating leaves on petiole up to 100 cm. Blades lanceolate to oblong, up to 30 cm. Inflorescence yellow/white, 2 spikes, flowers arranged in all directions along spike. Perennial, leaves in basal rosette, generally submerged, sometimes floating, lanceolate, up to 40 cm long. Inflorescence white/pink, 2 spikes, flowers arranged in rows on one side of spike only. Habitat: Still/flowing waters to 2 m deep. Habitat: Shallow (usually <15 cm) water, ephemeral pools, wetlands. Example location: Njelele Stream Family: Araliaceae Hydrocotyle bonariensis Lam. 3 Family: Azollaceae Azolla filiculoides Lam. 4.5 Leaf blades peltate (i.e. attached to petiole like an ‘umberella’); petioles up to 30 cm. Flowers inconspicuous. Plant creeping Annual or perennial. Unrooted, free-floating fronds, usually <2.5 cm side. Often forms dense green, purple or reddish mats. Shoots irregularly branched. Has single rootlets hanging down beneath the frond, distinguishing the species from native Azolla pinnata which has 2-3 roots per node. Habitat: shallow water and river edges. Habitat: still or slow-flowing water. Example location: Musola Stream, Fibwe weir. Notes: introduces from America, naturalised in southern Africa. Family: Ceratophyllaceae Ceratophyllum demersum 4 Shoot tip with shortened internodes. Most leaves 1-2 times forked, usually hard, bight or olive green, with marginal teeth. Rootless but usually associated with sediment. Family: Characeae Nitella sp 3.5 Multicellular branched alga up to several cm long. Pale, translucent green Habitat: submerged in still or slow-flowing water. Habitat: still or slow flowing, usually nutrient rich water. Example location: Kasanka River (pontoon); Musola river. Family: Commelinaceae Commelina diffusa subsp. Scandens (C.B. Clarke) Obermeyer a, terminal part of flowering shoot (2cm) b, flower (2mm) Clasping leaf sheaths and blades differentiated; leaves arranged spirally or in two rows. Flowers with one small and two large petals; usually blue. Habitat: Stream edges and slightly drier areas of seasonally flooded swamps and dambos. 4 Family: Commelinaceae Commelina fluviatilis Brenan. Perennial, sometimes annual, stems 15-180 cm, floating or trailing on water surface. Leaf sheaths 0.5-3 cm with purple stripes, Blades narrow-linear, 5-25 cm long, 0.1-0.4 cm wide. Single flower with two upper and one lower petal; mauve, blue or white. Habitat: river edges and permanently wet places. Sometimes part-submerged 3 Family: Commelinaceae Floscopa glomerata 3 Family: Convolvulaceae Ipomea aquatica Forsskål 4* a, part of flowering shoot 92cm); b, capsule with sepals (1cm); (c) seed (2mm) a b c Perennial, sometimes annual, stems creeping and rooting, up to 60 cm, Leaf sheaths approx 1.2cm with stripes, Blades linear, 5-8 cm long, 0.4-1.2 cm wide. Inflorescence, dense terminal panicle.2-4 cm long with gland-tipped hairs. Flower petals 3, unequal, pink to mauve. Variable species Habitat: river edges and swamps, often straggling into water. Perennial or annual; stems hollow, swollen, trailing or floating in water, up to 3 m. One leaf at each node; blades heart/arrow shaped on petioles up to 25 cm long. Flowers solitary, large, funnel shaped, pink or white. Example location: Musola river, Fibwe weir. Habitat: floating in still or slow-flowing water. Family Cyperaceae Cyperus alopecuroides 4 Family Cyperaceae Cyperus articulatus a, inflorescence (some bracts removed) (4 cm); b, spike (1 cm); c, spikelet (1.5 mm); d; glume (0.6 mm) with cross section of nut Tufted perennial; very short rhizomes; culms robust, smooth, 3sided above, to 150 cm. Leaves 3 – 5, W-shaped cross section. Bracts 4 – 7, the lower ones much overtopping the inflorescence, up to 65 cm long. Compound inflorescence with one stalk-less and several stalked clusters of spikes. Habitat: river edges, lakes, pools and wetlands. Robust leafless perennial; long, creeping rhizomes; culms arranged in a row at 1-3 cm intervals.; stiff, 80-160 cm tall; rounded, pith-filled with visible transverse septa. Inflorescence a panicle Habitat: in rivers, lakes, pools and wetlands in water up to 1 m deep; often forms large stands. 4 Family Cyperaceae Cyperus difformis 3.5 Family Cyperaceae Cyperus digitatus 4 a, flowering plant (2 cm) b, cluster of spikelets (4 mm) c, spikelet (1 mm) Slender annual. Leaves shorter than culm. Culm rounded to 3angled, generally up to 40 cm tall. Flower almost spherical spikelets arranged in clusters on a short rachis; leaves welldeveloped, > 3cm long. Robust perennial. Leaves > 3 cm long; culms clearly 3-winged below inflorescence, 50 – 160 cm tall; spikelets in spikes (each spike at some distance apart on an elongated rachis); inflorescence of one or more spike(s) at right angles to rachis. Habitat: shallow water and seasonally flooded areas; often abundant, forming large patches. Habitat: in or near open water, along riverbanks and in wetlands. Family Cyperaceae Cyperus papyrus 3.5 Family Cyperaceae Eleocharis acutangula 3* Tufted, stoloniferous perennial, 6-140 cm tall, leaves absent. Inflorescence a single terminal spikelet without bracts. Culms solid (pale green and spongy inside). Sharply 3-angled below spikelet. Sometimes forms large tussocks. a, terminal part of spikelet (2 mm) b, inflorescence (10 cm) c, whole plant (20 cm) Tufted perennial; very short rhizomes; culms robust, smooth, 3sided above, to 150 cm. Leaves 3 – 5, W-shaped cross section. Bracts 4 – 7, the lower ones much overtopping the inflorescence, up to 65 cm long. Compound inflorescence with one stalk-less and several stalked clusters of spikes. Habitat: river edges, lakes, pools and wetlands. Habitat: in water to 1 m deep. Still water and seasonally flooded areas a, spikelet (1 cm) b, glume (1 mm) c, fruit (0.5 mm) d, base of plant (2 cm) Family Cyperaceae Eleocharis atropurpurea 2 Family Cyperaceae Eleocharis caduca 3* Small tufted annual (sometimes perennial), forming mats at edge of water, or sometimes emergent. Leaves generally absent. Culms 3-15 cm, angular. Inflorescence a terminal, narrow spikelet without bracts. Slender annual. Culms 1-10 cm tall, 0.2-0.4 mm diameter. Spikelets (inflorescence) ovoid, 2-8 mm long, 1.5-2 mm diameter. Flowers January-may. Habitat: shallow still or slow flowing waters. a, flowering plant (2 cm) b, immature spikelet (2 mm) c, fruit (0.3 mm) Habitat: semi-emergent in still or very slow-flowing water and drying pool margins, often forming a turf. Family Cyperaceae Eleocharis decoriglumis 2 Family Cyperaceae Eleocharis dulcis 2.5 Annual. Culms tufted, 20-50 cm tall, 2-4 mm diameter; bluntly 3angled, spongy inside. Spikelets wider than culm; cylindrical approx. 3 cm long, 3 mm diameter. Tall tufted perennial 40-100 (-300) cm tall. Leaves absent. Inflorescence a single terminal spikelet (6 mm), cylindrical, tapering at tip and narrower than culm. Habitat: shallow still or slow flowing waters and seasonal pools. Habitat: Grows in water (sometimes submerged up to 3 m deep) and in pond margins. Family Cyperaceae Eleocharis geniculata 3* Family Cyperaceae Eleocharis limosa 3* Tufted perennial, 20-60 cm tall with Woody rhizomes. Leaves absent. a Inflorescence a single terminal spikelet. Densely tufted annual 15-25 cm tall. Leaves absent. Often grow in clumps. Culms culms filled with pale brown pith and longitudinal stripes. Spikelet almost spherical, wider than culm. Habitat: shallow, still water and wetland areas. Culms slender with transverse septa. b Habitat: shallow, still or slowflowing water. a, spikelet (2 cm) b, (alternative) proliferating spikelet (2 cm) c, fruit (0.5 mm) c a flowering spikelet (0.8 mm) b immature spikelet (0.8 mm) c fruit (0.5 mm) Family Cyperaceae Eleocharis naumanniana 2.5 Submerged perennial (occasionally annual), threadlike with branches in whorls. Septa visible at 2-2.5 mm intervals. Spikelets narrow ovoid, 5-6 mm long, 0.5-0.7 mm diameter. Habitat: submerged, free-floating with emergent spikelets. Low nutrient, still or slow flowing water. Forms mats when stranded. Family Cyperaceae Fuirena umbellata 2.5 Perennial, up to 1.5 m tall. Culm and leaf sheaths sharply 5-riged, leaves much shorter than culm, with hairy ligule. Inflorescence of 2-20 clusters of spikelets. Habitat: Still or slow flowing water, lake margins and wetlands.. Family Cyperaceae Schoenoplectus brachyceras 4 Stout perennial with woody rhizome with culms arising in a row. Culms 3-sided 60->100 cm tall. Lower involucral bract boat shaped and shorter than inflorescence (up to 5.5 cm). Sheath at base of culm has ‘ladder-like’ markings. Leaves reduced to scales. Family Cyperaceae Schoenoplectus confusus subsp. confusus 2.5 Habitat: in open water and along edge of streams and rivers. Tufted perennial with short rhizome. Culms 3-angled, 40-110 cm tall, 2-4 mm diameter; soft and pith filled. Lower involucral bract (up to 10 cm) stiff and overtops inflorescence. Leaves reduced to scales Notes: used for weaving baskets. Habitat: in open water up to 50 cm and seasonal wetlands. Family Cyperaceae Schoenoplectus corymbosus 3 Stout perennial with woody rhizome with culms arising in a row (sometimes tufted). Culms 3-sided 60->100 cm tall with longitudinal ridges. Lower involucral bract (up to 10 cm) stiff and overtops inflorescence. Leaves reduced to scales. Habitat: in open water up to 1 m and along edge of streams and rivers. Notes: used for weaving mats and baskets. Family Cyperaceae Schoenoplectus decipiens Tufted or spreading perennial with variable rhizome. Culms 8-80 cm tall, 1.5-4 mm diameter; usually rounded and pith-filled. Spikelets (groups of 1-6) usually sessile, 5-10 mm long, 3-5 mm diameter. Leaves reduced to sheaths. Habitat: seepage areas and along edge of open water 3 Family Cyperaceae Schoenoplectus triqueter a 3* Family Cyperaceae Websteria confervoides 3 Robust perennial, leaves reduced to 1-3 sheaths. Inflorescence (3-15 spikelets) appears lateral with lower involucral bract continuing above. Culms and bract sharply 3angled. Habitat: shallow, still water and wetlands. b c Submerged perennial (sometimes annual). Stems very fine (often <1 mm), numerous, green or reddish-brown, up to 100 cm long and often arising in whorls. Leaves reduced to scales <1 mm long. Inflorescences 1-4 oblong spikelets 5-12 mm long. Habitat: submerged, free-floating. Low nutrient, still or slowflowing water. Rare, but may be locally abundant, forming single species stands. a, spikelet (5 mm); b, fruit (2 mm); c, small flowering plant (0.5 mm) showing cross sections Family: Elatinaceae Elatine ambigua 4* Small annual (sometimes perennial); in water spreading up to 10 cm, on land smaller. Stems round, fleshy. Small lanceolate leaves, in opposite pairs. Small flowers in leaf axils. Forms a turf in shallow water. Habitat: Seasonally or totally submerged along river edges and ponds; usually in nutrient rich water on fine mineral soils. Family: Eriocaulaceae Eriocaulon dregei Robust perennial, leaves in rosettes arising from a creeping rhizome. Leaves liner, 10-25 cm long, up to 10mm wide. Scape (flowering stem) usually solitary, up to 35 cm long and 1 mm in diameter; 5-7 ribbed and usually shorter than the leaves. Flowering heads generally spherical and appearing ‘dirty white’ Habitat: fast-flowing perennial headwater streams. 3 Family: Hydrocharitaceae Lagarosiphon ilicifolius 4 Family: Hydrocharitaceae Ottelia exserta 3* Rooted; many floating leaves, 513 cm long, up to 7 cm wide. Prickles on peduncle and spathe (below flower); Flowers white. Perennial; stems robust (1.2-3 mm diameter). Leaves alternate, very occasionally in whorls, linear, curved, 4.5-13.5 mm long, 2-3.7 mm wide; thick and opaque with toothed margin. Vegetative parts totally submerged; can develop large colonies. Habitat: Slow to moderate flowing rivers. Habitat: Still or slow-flowing water up to 3 m deep. Family: Hydrocharitaceae Ottelia fischeri Rooted; floating paddle-shaped leaves with differentiated petiole. leaves (10-20 cm long) generally 1.5-2 times as long as broad. Spathes smooth. Habitat: moderate flow, lower nutrient rivers in water up to 1 m deep. 3 Family: Hydrocharitaceae Ottelia verdickii 2 Rooted. Submerged and (less commonly) floating leaves, ovate to lanceolate (20-80 cm long), gradually tapering to petiole; submerged leaves partially translucent. Habitat: in slow to moderate flowing water and flooded wetland areas. Example location: Musola stream at Fibwe weir. Family: Hydrocharitaceae Vallisneria spiralis 4 Family: Hydrostachaceae Hydrostachys polymorpha Usually perennial. Root thread-like, attached to rocks. Stems (15-75 cm long), thick and fleshy, with leaves reduced to scales. Flowers produced as river water level drops (with stem dying after fruit ripens) Rooted. Stems short, developing runners. Leaves arranged in two rows, or spirally; narrow, strap-like, up to 2 m or more long. With small spines on margin. Separate male and female flowers produced. Female flowers solitary, reaching surface on a spiral spathe up to 1 m long. Habitat: Fast-flowing, rocky, low nutrient rivers. Often under waterfalls. Habitat: widespread in still to moderate flow water. Example location: Mulembo River Notes: may become troublesome in irrigation and drainage ditches. Family: Juncaceae Juncus oxycarpus 3.5 3.5 Family: Lamiaceae Mentha aquatica 4* a, base with stolons (2 cm) b, flower (2 cm) c, flower (2 mm) d, fruit (2 mm) Tufted perennial with woody rhizomes. Leaves at base and on flowering stem (usually shorter than flowering stem) Septa visible on upper leaves. Generally 40-80 cm tall. Habitat: Widespread. Along stream and river banks and wetlands, growing in shallow water (often forming large stands). Inflorescence terminal, in 1-3 whorls; flowers mauve, bright violet or lilac. Tubular below. Stems up to 80 cm tall or trailing in water to 150 cm. Leaves opposite, sometimes hairy. Plants have and aromatic (minty) smell. Habitat: still and slow-flowing water and flooded areas. Sometimes floating on water surface. Family: Lentibulariaceae Utricularia inflexa 3 Carnivorous perennial herb. Plants lacking roots, but can be closely associated with the sediment. May be free-floating above sediment but submerged below water surface. Vegetative parts elongate, forked, with animal-catching bladders. Flowers with mauve to white petals with violet veins (rarely yellow with purple veins), covered with fine hairs. Spindle-shaped floats. 3.5 An aquatic fern. Rhizomes (up to 25 cm long and 1 cm tick) firmly attached to rocks and covered in brown scales up to 1 cm long. Leaves brownish and leathery, with weakly-toothed margin. Habitat: Attached to rocks in fast-flowing, water (generally with low nutrients), often in shaded areas. Example location: Mulembo River 2* Plants not rooted in sediment though often closely associated with it, or free-floating above sediment but below surface. Vegetative parts terete, elongate, forked, with animal-catching bladders. Lacking roots. Showy small uniformly yellow flowers. Habitat: shallow to deep, still to slow-flowing water: river backwaters, lakes, ditches etc. Habitat: shallow to deep, still to slow-flowing water: river backwaters, lakes, ditches etc. Family: Lomariopsidaceae Bolbitis heudelotii Family: Lentibulariaceae Utricularia stellaris Family: Lythraceae Rotala myriophylloides 4 Stems (up to 50 cm long, usually less) creeping, erect or floating. Leaves (up to 20 mm long) linear to lanceolate, terete, 2 at each node (sometimes in whorls (max. 8), particularly when submerged), often with both broad and narrow thread-like leaves; small flowers in leaf axils, petals <1.5 mm long, pink; stems often red Habitat: grows as a turf in wet conditions, and also submerged Family: Menyanthaceae Nymphoides indica 2 Family: Najadaceae Najas horrida 4 Leaves whorled (3 leaves minimum per whorl); linear or threadlike, not equally spaced around nodes (forming leaf clusters), toothed margins, basal leaf sheaths at least partly united with leaf. Flowers submerged, inconspicuous in leaf axils Floating leaves small (usually <25 cm across), flowers supported by floating leaf, usually white or yellow with 5 sepals, petals hairy Habitat: shallow to deep slow flowing water Habitat: Common and widespread in still and slow-flowing waters. Family: Nymphaceae Nymphaea divaricata 2 Family: Nymphaceae Nymphaea lotus 3 Rooted; leaves submerged or floating (8-24 cm); bi-lobed. Flowers blue, pink or yellow. Habitat: Slow flowing, nutrient poor waters Example location: Katete River, Shiwa Ngandu Notes: IUCN Red Data Book species (due to data deficiency) Floating leaves, ovate to circular, up to 59 cm long and wide, but usually slightly smaller. Leaves leathery, upper surface dark green, lower surface brownish; mature leaves with sharply toothed margin. Flowers held well above water; petals (up to 25), white or yellowish, 2-7 cm long. Stamens (up to 90), yellow, 1-4 cm long; separated from petals by a gap. Flowers scented at night. Habitat: still or slow-flowing permanent or temporary water up to 2.5 m. Family: Nymphaceae Nymphaea nouchali var. caerulea 3 Floating leaves variable but often > 25 cm across, with a deep sinus; flowers crown shaped, on a long pedicel, usually white, violet or blue , held c. 20 cm above or floating on surface; 12 – 24 hairless petals. 3.5 Perennial or annual. Creeping or mat-forming, stems rooting at nodes. Flowers sessile, solitary in leaf axils; Leaves in opposite pairs, rarely whorls of 3, abruptly narrowing into a winged petiole Habitat: riverbanks and backwaters. 4 Flower of 3–5 distinct sepals and/or petals. Sepals borne at top of ovary; flowers usually conspicuous, lemon-yellow with a dark spot at base of petal; stems may be creeping or floating; has distinctive silver-white spongy structures (pneumatophores) in clusters at nodes on floating stems. Habitat: wetlands, and floating on surface of slow-flowing rivers (often forming dense mats and colonised by other species) Habitat: fast to deep slow flowing water. Family: Onagraceae Ludwigia palustris Family: Onagraceae Ludwigia adscendens subsp. diffusa Family: Osmundaceae Osmunda regalis 3.5 Large rhizomatous fern, rhizome with many black fibrous roots and fronds. Fronds erect, 2-pinnate, up to 1 m long. Fertile pinnae (appearing rusty-brown) born at the apex of some fronds Habitat: found along banks of streams with variable flow. Family: Poaceae Leersia hexandra 4 Family: Poaceae Panicum parvifolium 2.5 With floating and/or ascending stems, with runners which may be several meters long when floating. Culm nodes swollen, hairy. Leaf sheaths with ear-like lobes, ligules membranous, asymmetric, leaf blades long and narrow a, flowering plant (3 cm) b, spikelet (2 mm) c, flower (2 mm) Habitat: in or floating on still or flowing water; may form large stands. Often floating on water surface, with ascending stems or flowerstalks; Leaf blades ovate to lanceolate, flat, lower ones with a grey-green bloom; leaf sheaths sometimes finely hairy above; ligules membranous, short. Leaf bases heart-shaped. Habitat: along streams and other permanent water; shade tolerant. Family: Poaceae Panicum repens 3 Floating and ascending stems; mat-forming, with long rhizomes or stolons. Leaf blades folded or in-rolled, hard, blue-green, waxy, terminating in a hard sharp point. Ligules short, membranous; white hairs on leaf behind ligule. Habitat: may for temporary mats along river edges; does not tolerate permanent flooding. Family: Poaceae Panicum subalbidum Robust tufted annual or short-lived perennial. Culms soft, leafy erect or creeping (60-200 cm long). Leaf sheaths papery, sometimes purple, ligules short (<1 mm); leaf blade flat or slightly folded, 7-50 cm long, 3-15 mm wide with distinct white midrib. Habitat: along edge of rivers and other open water, where it may form floating mats 4 Family: Poaceae Phragmites australis 4* Family: Poaceae Phragmites mauritianus 3 Reeds: tall and erect, up to 4 m; flower a feathery panicle leaf blades smooth on underside, with soft flexible tips; ligules with short (<2 mm) fringing hairs. Reeds: tall and erect, up to 4 m; culms woody and bamboo-like; flower a feathery panicle (green becoming purple-brown; leaf blades rough on underside, with sharp-pointed tips; ligules with long fringing hairs. Habitat: alongside rivers and streams and in shallow water; often locally dominant. a, inflorescence (10 cm) b, spikelet (3 mm) c, ligule (1 cm); d, base (10 cm) Family: Podostemaceae Ledermanniella tenax Habitat: alongside rivers and streams and in shallow water; often locally dominant. 3 Branched, submerged perennial. Stems tough, fleshy, up to 20 cm long. Dense, scale-like leaves (0.2-0.3 mm long on flowering stems. Flowers produced as water levels recede; seed capsules 8ribbed. Habitat: locally abundant forming reddish brown mats, attached to rocks at water level (sometimes submerged up to 50 cm); at edge of fast flowing water, or in water-spray. Flowering just above water level. Family: Podostemaceae Sphaerothylax spp. 4 Submerged herb. Distinct thalloid base (deeply lobed or ribbonlike) firmly attached to rocky substrate. Stems red, erect, 5-50 cm long. Leaves 1-7 cm long, simple or repeatedly forked. Younger stems leafy, older stems becoming tough and leafless; flowers spaced along the length on short stems (produced as water levels recede); seed capsules 8-ribbed. Habitat: locally abundant forming mats, attached to rocks at water level; at edge of fast flowing water Family: Podostemaceae Tristicha trifaria 3 Family: Polygonaceae Persicaria amphibia 4 a, ochrea of floating shoot (7.5 mm) b, flowering floating shoot (4 cm) c, flowering terrestrial shoot (4 cm) Submerged, firmly fixed to rock substrate. Basal parts ribbon-like, looking like treads stuck to rock. Flowering shoots short and leafy, leaves very small. Flowers produced as water levels recede; seed capsules 3-valved. Habitat: locally abundant forming reddish brown mats, attached to rocks at water level (sometimes submerged up to 50 cm); at edge of fast flowing water, or in water-spray. Flowering just above water level. Family: Polygonaceae Persicaria attenuata 4 Floating and sometimes emergent leaves. Leaf blades inserted at base of sheath; veins pinnately branched; usually with pink flowers on a solitary terminal spike. Ochrea mouth lacking a fringe of bristles or hairs. Leaf bases abruptly rounded to heart shape; leaves never densely hairy in aquatic form. Habitat: amphibious; in water occurs in a wide variety of waterbodies, streams and swamps. Tends to occur at high altitude. Family: Polygonaceae Persicaria decipiens 3.5 Stout, often shrubby perennial, covered with soft hairs. veins pinnately branched; usually with pink flowers (or white with pinkish bases); Ochrea mouth with a fringe of hard bristles or hairs. Spikes dense, stout, erect. Annual or perennial. Leaf blades sessile; veins pinnately branched; usually with pink or white flowers; Ochrea with a fringe of long hairs (usually 10 mm or more long) and covered with small ascending bristles. Spikes hanging or erect. Habitat: emergent in still waters and wetlands; sometimes forms large stands. Habitat: emergent in still waters and wetlands; sometimes forms large stands. Family: Polygonaceae Persicaria hydropiper 4.5 Annual. Stems erect, sometimes creeping and rooting, generally 20-60 cm tall. Ochrea tubular, up to 2 cm long, with sort white fringing hairs up to 6mm long. Leaves with short petioles; blades narrow-lanceolate, up to 15 cm long. Inflorescence of 3-5 segments, pink to greenish-white 4.5 a, flowering shoot (4 cm) b, nut (fruit) (2.5 mm) c, ochrea (1 cm) Erect robust perennial. Leaf veins pinnately branched; usually with pink flowers. Ochrea with no bristles or hairs. Leaf bases gradually narrowing into petiole; leaves not floating; often thickly covered in whitish hairs, giving plant a pale whitish appearance. Habitat: emergent in still waters and wetlands 3 Annual. Stems erect or lying on ground, generally 30-120 cm long. Ochrea loosely tubular, 2-4 cm long, without white fringing hairs at mouth. Leaves with short petioles; blades narrow-lanceolate to ovate, up to 25 cm long, gland-dotted, and under-surface with fine white hairs. Inflorescence usually terminal, and dense. Habitat: along edge of open water and rivers, sometimes forming floating mats on water (where internodes may be swollen) Habitat: wet areas and along edge of open water and rivers. Family: Polygonaceae Persicaria senegalensis Family: Polygonaceae Persicaria lapathifolia Family: Pontederiaceae Eichhornia crassipes 4.5 Usually perennial, usually floating, forming mats. Leaf petiole up to 30 cm long, swollen and spongy; leaf blades flattened. Inflorescence a blue spike up to 50 cm long. Habitat: free-floating in a wide variety of aquatic habitats; thrives in high nutrient conditions. Notes: introduced to southern Africa from tropical South America in 19th Century; can cover vast areas of water, becoming a weed problem. Family: Pontederiaceae Eichhornia natans 3 Annual or perennial, forming dense submerged mats. Differentiated into (many) submerged, linear leaves up to 8 cm long, and (fewer) floating heart-shaped leaves (petiole up to 10 cm long, but usually shorter); blade 1-2.5 cm long, 1-1.5 cm wide. Inconspicuous inflorescence, mauve or white. Habitat: backwaters and slow-flowing rivers up to 1 m deep, usually at restricted altitude of around 1000 m. Family: Potamogetonaceae Potamogeton octandrus 4* Leaves regularly dispersed along stems, narrowly elliptical to lanceolate, 160-280 long, 22-38 mm broad, acute at apex; floating leaves shiny and waxy (also has submerged leaves); all leaves with long petioles, and elongated membranous stipules; at least some submerged leaves persistent after floating leaves develop. Flowers emergent and inconspicuous. Habitat: still to moderate-flow waters of variable depth. 3 Perennial. Stems 20-100 cm or more long. Produces very narrow submerged leaves and leathery oblong to elliptical floating leaves (1-3 cm long, 3-11 mm wide). Leaf margins entire, midribs with broad gas channels on either side. Flower spikes usually developing only in axils of floating leaves. Habitat: In still or slow-flowing waters. Family: Potamogetonaceae Potamogeton nodosus Family: Potamogetonaceae Potamogeton schweinfurthii 4 Perennial, sometimes with woody rhizome; stems 30-200 cm long; leaves submerged and sometimes floating, with persistent stipule up to 6.2 cm long. Submerged leaves up to 24 cm long (4-21 times as long as wide), yellow-green to brownish. Distinct midrib, may have gas-filled channels on each side; minutely-toothed. Petioles of floating leaves up to 63 mm long, but shorter than blade. Flower spikes cylindrical, 3-9 cm long Habitat: still to moderate-flow water up to 3 m deep. Family: Potamogetonaceae Stuckenia pectinata 3 Family: Ranunculaceae Ranunculus multifidus 4 Submerged perennial. Narrow stems and leaves, with stipules arising from the leaf sheaths, which wrap around the stem. A pair of gas filled channels runs parallel to the midrib, giving the leaf the appearance of a double pipe when cut in cross section. Spikes with up to 5 pairs or whorls of flowers, on long floating stems (up to 45 cm). Habitat: Still and flowing waters across a very wide range of water chemistry conditions, but preferring nutrient rich waters. a, flowering shoot (2 cm) b, stipule (3 mm) c drupelet (fruit) (1.7 mm) Perennial with stems usually < 1 m tall, some creeping and rooting, hairs pointing towards stem tips; leaves in basal rosettes and along stems; yellow flowers with 5 sepals. Habitat: wetlands and along rivers and ditches Family: Salviniaceae Salvinia molesta 3.5 Family: Scrophulariaceae Bacopa floribunda 1 Annual. Stems erect, 4-sided, usually branched, hollow with a ring of large gas-filled channels. Flowers on short stalks in leaf axils, usually white with purple veins. Small thread-like bracteoles beneath flowers. Perennial floating fern, stems without true roots. Irregularly forked, but may be up to 30 cm. Leaves in whorls of three; floating leaves have ‘egg whisk’ hairs (usually <1 mm). Habitat: variety of still and slowflowing habitats. Thrives under high nutrient conditions Notes: can be a problem weed (Kariba Weed) Habitat: Forms dense mats in marshy places, banks of streams and pools; often submerged in water but can grow amphibiously a, flowering shoot (2 cm) b, flower (1 cm) c, anther (1 mm) Family: Scrophulariaceae Limnophila ceratophylloides 3 Family: Scrophulariaceae Limnophila bangweolensis 1 Amphibious annual. Stem (up to 50 cm long) and aerial parts covered with dense, white hairs. Flowers sessile or nearly so, in spikes or solitary; usually two-lipped and tubular below, pink, lilac or mauve. Submerged leaves (up to 1.8 cm long) whorled, divided to the midrib, usually pinnate; aerial leaves (up to 9 mm long and 2 mm wide) mostly opposite, ovate, with toothed margins Habitat: shallow rivers, streams (slow to moderate flow), lakes and ponds. Amphibious perennial (sometimes annual), very variable in form. Stem up to 80 cm long, simple or branched. Submerged leaves (625 cm long) whorled, pinnate, divided into thread-like segments; aerial leaves (5-9 mm long, 1-2 mm wide), lobed or divided almost to base. Habitat: shallow to deep rivers, streams (slow to moderate flow), lakes and ponds. Family: Scrophulariaceae Mimulus gracilis 3 Perennial, sometimes annual. Stems erect or trailing, generally 2050 cm tall; 4-sided with ‘wings’ on the angles. Leaves in opposite pairs, sessile, margins slightly toothed. Flowers (yellowish) solitary in leaf axils on stems 1-3.5 cm long. A very variable species. Habitat: moist places, in standing water and along river banks. Flowers January-April; flowers opening after late-morning Family: Scrophulariaceae Torenia thouarsii 2.5 Slender annual. Stems erect or trailing, up to 40 cm long; 4-sided with ‘wings’ on the angles. Leaves, in opposite pairs, petioles (0.55 mm long) usually hairy; blades 1.2-2 cm long, 8-15 mm wide. Flowers pale blue, pink or white with dark blue or violet markings; born in pairs in leaf axlis on stems up to 22 mm long. Habitat: sometimes grows in water or along river edges; may grow on floating vegetation. Family: Thelypteridaceae Thelypteris confluens 3 Family: Thelypteridaceae Thelypteris interrupta 3.5 Perennial fern. Creeping rhizome (around 2 mm thick) covered with brown scales. Leaves erect, arising at intervals of 1-5 cm along rhizome. Leaf blades (<45 cm long) developing in full sun usually soft and flexible. Leaflets deeply lobed, divided almost to midrib. Perennial fern. Creeping rhizome (up to 6 mm thick. Leaves erect, arising at intervals of 2-12 cm along rhizome. Leaf blades (up to 80 cm long) developing in full sun usually stiff, thick and leathery; more flexible and thinner when developing in shade. Leaflets not deeply lobed, divided, at most, halfway to midrib. Habitat: permanently wet areas and along river margins; may be locally dominant. Habitat: permanently wet areas and along river margins; may be locally dominant. Family: Trapaceae Trapa natans 4.5 Annual or short-lived perennial. Floating-leaves and rooted in sediment. Floating leaves simple. Leaf blades form a neat circular mosaic of leaves on water surface, often pink-brown in colour (submerged leaves may also be present); fruits with 2 or 4 hard horns Habitat: still or slow-flowing water Family: Typhaceae Typha domingensis 4 Large, robust perennial. Emergent plants with 2 opposite rows of long, narrow basally-inserted and often spirally-twisted leaves, up to 3 m long; leaf sheaths sloping. Cylindrical flower heads; male spike separated from female spike by 1–3 cm gap. Habitat: Often forming large stands in shallow waters, still river margins and wetlands. Example location: Musola stream Family: Xiridaceae Xyris anceps 2.5 Annual or sometimes perennial, 2-8 leaves (between 8-40 cm long, up to 10 mm wide) with brownish bases. Emergent plants with short basally-inserted leaves and long flowering stalks emerging from the base of the plant; conspicuous yellow petals on inflorescence. Bracts with a dull grey patch just below the tip. Family: Xiridaceae Xyris gerrardii 1.5 Tufted perennial. Rhizomes with persistent brown leaf bases. Leaves clustered on rhizome, bases dark brown to almost black. Leaf blades flat, twisted, furrowed; 20-35 cm long, >1 mm wide. Papery edges of flower bracts become torn with age. Habitat: High altitude wetlands areas, and along river margins. Habitat: still or slow flowing river margins, wetlands and lakes; often forming large clumps. GLOSSARY ACUTE: sharply pointed but not drawn out; making an angle of less than 90º. BRACT: a modified leaf attached below a an inflorescence or flower. BRACTEOLE: small bract attached to the flower stalk (pedicel). CAPSULE: a dry fruit splitting over 2 or more lines. CULM: stem bearing the inflorescence in Cyperaceae and Poaceae families. ELIPTICAL: oval in outline; widest in middle, narrowest at ends. INTERNODE: part of the stem between 2 nodes. INVOLUCRE: a collection of bracts or leaves underneath a flower or cluster of flowers. LANCEOLATE: narrow, widest in middle, narrower at both ends. LEAF BLADE: flat, expanded portion of a leaf. LEAF SHEATH: tubular, unexpanded portion of a leaf surrounding stem. LIGULE: small projection at top of leaf sheath in Cyperaceae and Poaceae. NODE: joint where a leaf, branch or bract is borne. OCHREA: a sheath above the node in Polygonaceae. PANICLE: compound or stalked inflorescence with stalked flowers. PEDICEL: stalk of a solitary flower. PEDUNCLE: stalk of an inflorescence or flower cluster. PELTATE: leaf blade attached to its stalk inside the margin. PETIOLE: differentiated narrowed part of the leaf attaching it to the stem. PINNATE: compound leaf with leaflets PITH: soft spongy content of stems, scapes and leaves. RHIZOME: thickened stem with root-like appearance creeping on surface or underground; sending off roots and the tip sending up progressive leaves or stems. SCAPE: flowering stem of a plant where all leaves are basal. SEPTA: separate walled cavities within a stem. SESSILE: without a stalk. SINUS: space between two lobes of a leaf. SPATHE: the bract or pair of bracts surrounding, beneath or close to an inflorescence. SPIKE: inflorescence with a central stalk bearing sessile (or nearly so) flowers. STIPULE: appendage at the base of a leaf, usually in pairs. STOLON: creeping stem at or below surface, giving rise to new stems. TERETE: circular in cross section. THALLUS: plant body not differentiated into stem and leaves. REFERENCE Cook, C.D.K. (2004). Aquatic and Wetland Plants of Southern Africa. Backhuys, Leiden, The Netherlands