Juncaceae Juss.

Milliken, W., Klitgard, B. and Baracat, A. (2009 onwards), Neotropikey - Interactive key and information resources for flowering plants of the Neotropics. http://creativecommons.org/licenses/by/3.0

Morphology General Habit

Perennial and usually rhizomatous or rarely annual herbs, glabrous or with hairy leaf margins

Vegetative Multiplication Rhizomes

Rhizome creeping, ascending or erect, unbranched or branched, naked or covered by scales or splitting leaf bases

Morphology Culms

Culms erect, ascending or rarely procumbent, terete (rarely flattened, J. ensifolius Wikstr.), smooth or longitudinally ridged, naked or leaf bearing

Morphology Leaves

Leaves linear or filiform, with an open and sometimes auriculate or closed sheath, spirally arranged or rarely distichous, blades sometimes reduced

Morphology Reproductive morphology Inflorescences

Inflorescence terminal, sometimes pseudolateral, compound, cymose or racemose, usually in heads or spike -like clusters, rarely reduced to a single terminal or lateral flower

Morphology Reproductive morphology Flowers

Flowers generally small, tepals; 8mm long, perfect or imperfect, actinomorphic

Morphology Reproductive morphology Flowers Perianth

Perianth segments 6 in 2 whorls of 3, glumaceous, equal or almost equal, free

Morphology Reproductive morphology Flowers Androecium Stamens

Stamens 6 in 2 whorls of 3, opposite the perianth segments, inner whorl sometimes reduced; filaments filiform or somewhat flattened and widened at base; anthers oblong to linear, basifixed, obtuse or mucronate, dehiscing by 2 longitudinal lateral slits

Morphology Reproductive morphology Flowers Gynoecium Carpels

Carpels 3, connate; ovary superior, 1-locular, 3-septate or 3-locular; style 1, up to 10 mm long but usually shorter; stigmas 3, terete and of equal diameter throughout or sometimes tapering distally, twining with adaxial papillae; fruit an orbicular to oblong or ellipsoidal, 3- lobed, round or trigonous, loculicidal or circumscissile capsule

Morphology Reproductive morphology Seeds

Seeds usully many per capsule, sometimes 3; outer seed coat hyaline, whitish or light brown, sometimes drawn out into tail-like appendages, often with distinct sculpturing; inner seed coat brown to castaneous or yellow.

Diagnostic

Grass-like. Smooth herbs. Without silica. Distinguishing characters (always present): Trimerous (very rarely dimerous), pentacyclic (rarely tetracyclic) flowers. Glumaceous tepals. Tricarpelate (very rarely bicarpelate) ovary. Capsule. 3 (Luzula) or more seeds. Distichia - cushion forming, leaves distichous, flowers unisexual. Juncus - grass-like, smooth, many-flowered culms, many seeded capsules. Luzula - grass-like, hairy leaf margins, many-flowered culms, 3-seeded capsules. Oxychloe - cushion forming, leaves prickly, flowers with two bracteoles. Patosia -  cushion forming, leaf margin finely serrate, flowers with one bracteole. Rostkovia - grass-like, single-flowered culms, capsule orbicular and many seeded. Key differences from similar families: Juncaceae are grass-like herbs with herbaceous culms, linear leaves, and usually many flowered inflorescences of small glumaceous flowers - just like Poaceae and Cyperaceae. Juncaceae differ from both these families in having: Smooth leaves and culms without silica encrustations. Complete whorls of 3+3 tepals. Usually 3+3 stamens. Gynoecium of 3 carpels. Fruit with at least 3 seeds and usually many more.

Note

Number of genera: Five: Distichia JuncusLuzula Oxychloe Patosia Rostkovia The complete trimerous, pentacyclic flowers and the capsular fruit delimits Juncaceae morphologically from other glumiflorous families such as Poaceae and Cyperaceae and the grass-like habit and internal anatomy separates it from the related Thurniaceae. Molecular data suggest that Juncaceae and Cyperaceae are sister taxa and that together they are sister to Thurniaceae (Jones 2005).

Distribution

Juncaceae are native in alpine meadows and in grasslands, especially in the highlands, where they may be weedy. Some are endemic to the Andes (all Distichia, Oxychloe, Patosia and species of Juncus and  Luzula), whereas other are widespread, often temperate species. Distichia Nees & Meyen in the Andes from Colombia to northernn Chile/Argentina. Luzula DC. and Juncus L. mostly in the temperate zone and at high elevations in the tropical zone. Oxychloe Phil. in the Andes from Patagonia to Peru. Patosia Buchenau in the Andes from Bolivia to northern Chile/Argentina. Rostkovia Desv. in southernmost South America and Ecuador.

Juncaceae, Susan Carter. Flora of Tropical East Africa. 1966

Morphology General Habit

Annual or perennial herbs, rarely shrubs

Morphology Roots

Roots fibrous

Morphology Stem

Stems erect, cylindric or rarely compressed, naked or leafy, sometimes rhizomatous or stoloniferous, and then horizontal or ascending

Morphology Leaves

Leaves grass-like or cylindric, sheathing at the base, sometimes reduced to cataphylls; sheaths open and sometimes auriculate, or closed

Morphology Reproductive morphology Inflorescences

Inflorescence terminal, often pseudo-lateral, compound or rarely simple with one flower, umbellate, paniculate, the flowers solitary or in capitula (heads); bracts leaf-like, scarious or membranous, persistent; bracteoles sometimes present

Morphology Reproductive morphology Flowers

Flowers small, regular, hermaphrodite; rarely the plants dioecious

Morphology Reproductive morphology Flowers Perianth

Perianth-segments 6, in two series, subequal, glumaceous, green or brown, usually membranous at the edges

Morphology Reproductive morphology Flowers Androecium

Stamens 6, opposite and shorter than the perianth-segments, the 3 inner sometimes absent; filaments linear or triangular; anthers basifixed, 2-thecous, introrse, dehiscing longitudinally

Morphology Reproductive morphology Flowers Gynoecium

Carpels 3, joined; ovary superior, 1- or 3-locular; style rarely absent; stigmas 3

Morphology Reproductive morphology Fruits

Fruit a loculicidal capsule

Morphology Reproductive morphology Seeds

Seeds 3 or many, ovoid to obovoid, apex sometimes apiculate, base sometimes tailed

Gemma Bramley, Anna Trias-Blasi & Richard Wilford (2023). The Kew Temperate Plant Families Identification Handbook. Kew Publishing Royal Botanic Gardens, Kew

Recognition

Characters of similar families: Cyperaceae: culms 3-sided, leaves usually 3-ranked, flowers minute, perianth reduced to bristles, rarely tepals, or 0, fruit a 1-seeded nutlet. Poaceae: culms rounded or flattened and always hollow and noded, leaves 2-ranked, lemma and palea present in floret, fruit a caryopsis. Restionaceae: plants mostly dioecious, leaves usually reduced to sheaths, flowers mostly unisexual, minute and regular, perianth of 6 tepals, fruit a 1–3-locular capsule or nutlet.

Morphology General Habit

Herbs, usually rhizomatous, rarely annual-Culms erect or rarely procumbent, terete or rarely flattened, without nodes

Morphology Leaves

Leaves linear to filiform, spirally arranged or rarely distichous, glabrous or sometimes hairy, blades sometimes reduced to a bladeless sheath

Morphology Reproductive morphology Inflorescences

Inflorescence terminal, sometimes pseudolateral, compound, racemose or cymose, in heads or spike-like clusters, rarely a single terminal or lateral flower

Morphology Reproductive morphology Flowers

Flowers small to minute, regular

Morphology Reproductive morphology Flowers Perianth

Perianth comprising glume-like tepals

Morphology Reproductive morphology Flowers Corolla

Tepals 6, in 2 whorls of 3, 8 mm or more long, acute at apex, ± equal-Stamens 6, in 2 whorls of 3, inner whorl sometimes reduced

Morphology Reproductive morphology Flowers Gynoecium Stigma

Stigmas 3

Morphology Reproductive morphology Fruits

Fruit a 3–many-seeded capsule, oblong to orbicular or ellipsoid, 3-lobed

Morphology Reproductive morphology Seeds

Seeds sometimes with tail-like appendages, often with distinct sculpturing on surface, whitish to brown or yellowish.

Distribution

Eight genera and 470 species. Widespread in both northern and southern hemisphere temperate regions, as well as at higher altitudes in the tropics. The largest genera are Juncus (331 species) and Luzula (123 species).

Note

Rhizomatous or annual herbs. Culms mostly terete. Leaves mostly linear, glabrous, sometimes hairy. Flowers small to minute, regular. Perianth of 6 tepals, 2 whorls of 3. Fruit a capsule. Seeds 3–many.

Description Author

David A. Simpson & Martin Xanthos