Annual or perennial herbs, or tall woody bamboos. Flowering stems (culms) jointed, internodes hollow or solid; branches arising singly from nodes and subtended by a leaf sheath and 2-keeled prophyll, often fascicled in bamboos. Leaves arranged alternately in 2 ranks, differentiated into sheath, blade, and an adaxial erect appendage at sheath/blade junction (ligule) ; leaf sheath surrounding and supporting culm-internode, split to base or infrequently tubular with partially or completely fused margins, modified with reduced blade in bamboos (culm sheaths) ; leaf blades divergent, usually long, narrow and flat, but varying from inrolled and filiform to ovate, veins parallel, sometimes with cross-connecting veinlets (especially in bamboos) ; ligule membranous or a line of hairs. Inflorescence terminal or axillary, an open, contracted, or spikelike panicle, or composed of lax to spikelike racemes arranged along an elongate central axis, or digitate, paired, or occasionally solitary; axillary inflorescences often many, subtended by spatheoles (specialized bladeless leaf sheaths) and gathered into a leafy compound panicle; spikelets often aggregated into complex clusters in bamboos. Spikelets composed of distichous bracts arranged along a slender axis (rachilla) ; typically 2 lowest bracts (glumes) empty, subtending 1 to many florets; glumes often poorly differentiated from accompanying bracts in bamboos. Florets composed of 2 opposing bracts enclosing a single small flower, outer bract (lemma) clasping the more delicate, usually 2-keeled inner bract (palea) ; base of floret often with thickened prolongation articulated with rachilla (callus) ; lemma often with apical or dorsal bristle (awn), glumes also sometimes awned. Flowers bisexual or unisexual; lodicules (small scales representing perianth) 2, rarely 3 or absent, 3 to many in bamboos, hyaline or fleshy; stamens 3 rarely 1, 2, 6, or more in some bamboos, hypogynous, filaments capillary, anthers versatile; ovary 1-celled, styles (1 or) 2(rarely 3), free or united at base, topped by feathery stigmas, exserted from sides or apex of floret. Fruit normally a dry indehiscent caryopsis with thin pericarp firmly adherent to seed, pericarp rarely free, fleshy in some bamboos; embryo small or large; hilum punctate to linear.
About 700 genera and 11,000 species: widely distributed in all regions of the world.[1]
There are approximately 9 species, subspecies, varieties, forms, and cultivars in this genus: Y. australiensis · Y. australiensis var. australiensis · Y. australiensis var. intermedia · Y. foliolosa · Y. majuscula · Y. muelleri · Y. nulla · Y. pauciflora · Y. websteri
There are approximately 374 species, subspecies, varieties, forms, and cultivars in this genus. Here are just 100 of them: P. acutiflorum diminutum · P. acutiflorum vanbruntiae · P. boreale genuinum · P. boreale hingganicum · P. boreale macranthum · P. boreale nudipedum · P. brandegei mellitum · P. brandegei typicum · P. caeruleum vanbruntiae · P. californicum columbianum · P. carneum amoenum · P. carneum genuinum · P. coeruleum villosum · P. foliosissimum verum · P. lanatum boreale · P. occidentale typicum · P. pauciflorum stenocalyx · P. pulcherrimum hyperboreum · P. viscosum chartaceum · P. viscosum elegans · P. viscosum eximium · P. viscosum genuinum · P. viscosum lemmonii · P. viscosum mellitum · P. 'Apricot Beauty' · P. 'Apricot Delight' (Jacobs Ladder) · P. 'Bressingham Purple' (Bressingham Purple Jacob's Ladder) · P. 'Churchills' · P. 'Dawn Flight' · P. 'Daydawn' · P. 'Eastbury Purple' · P. 'Elworthy Amethyst' · P. 'Glebe Cottage Lilac' · P. 'Hannah Billcliffe' · P. 'Heavenly Blue' · P. 'Hidako White' · P. 'Hopleys' · P. 'Katie Daley' · P. 'Lace Towers' · P. 'Lambrook Mauve' · P. 'Lewdon Farm Pink' · P. 'Little Upcott' · P. 'Mary Mottram' · P. 'North Tyne' · P. 'Northern Lights' · P. 'Norwell Mauve' · P. 'Pam' · P. 'Pink Beauty' · P. 'Pink Pearl' · P. 'Polbress' · P. 'Prima Donna' · P. 'Ribby' · P. 'Sapphire' · P. 'Sonia's Bluebell' · P. 'Sunnyside Indigo' · P. 'Sunnyside Storm' · P. 'Theddingworth' · P. acaule · P. acutiflorum (Tall Jacob's-Ladder) · P. acutiflorum 'Wild Tall Jacob's Ladder' (Jacobs Ladder) · P. acutiflorum f. lacteum · P. acutiflorum occidentale · P. acutiflorum van-bruntiae · P. acutifolium · P. acutifolium var. nipponicum · P. albiflorum · P. album · P. ambervicsii · P. amoenum · P. antarcticum · P. antarcticum f. violascens · P. antarctinum · P. antarticum · P. archibaldae · P. archibaldiae · P. arcticum · P. bicolor · P. biflorum · P. boreale (Northern Jacob's-Ladder) · P. boreale 'Heavenly Habit' (Heavenly Habit Northern Jacobs Ladder) · P. boreale albiflorum · P. boreale album · P. boreale boreale · P. boreale humile · P. boreale richardsonii · P. boreale var. hyperboreum · P. boreale var. macranthum · P. boreale var. pulchella · P. boreale var. pulchellum · P. brandegeei (Brandegee's Jacob's-Ladder) · P. brandegeei mellitum · P. brandegei · P. brandegei f. lambornii · P. brandegei var. lambornii · P. brandegii · P. bursifolium · P. caeruleum (Charity) · P. caeruleum 'Album' (Jacobs Ladder) · P. caeruleum 'Apricot Delight' (Apricot Delight Jacobs Ladder) · P. caeruleum 'Bambino Blue'
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