Lesser Hop Trefoil

Foodplant / internal feeder
larva of Apion nigritarse feeds within inflorescence of Trifolium dubium
Remarks: Other: uncertain
Other: major host/prey

Foodplant / gall
larva of Apion pubescens causes gall of stem of Trifolium dubium

Foodplant / sap sucker
adult of Berytinus minor sucks sap of Trifolium dubium
Other: major host/prey

In Great Britain and/or Ireland:
Foodplant / parasite
conidial anamorph of Erysiphe trifolii parasitises live Trifolium dubium

Foodplant / saprobe
immersed, roundish, bright blackish-brown pycnidium of Stagonospora coelomycetous anamorph of Leptosphaeria pratensis is saprobic on dead stem of Trifolium dubium
Remarks: season: 11

Foodplant / pathogen
sporangium of Peronospora trifoliorum infects and damages live green parts of Trifolium dubium

Foodplant / parasite
amphigenous uredium of Uromyces anthyllidis parasitises live leaf of Trifolium dubium

Foodplant / parasite
aecium of Uromyces minor parasitises live Trifolium dubium

Erect or procumbent annual, stem usually pubescent. Leaflets 8-11 mm long, obovate or obcordate, terminal leaflet petiolulate. Stipules 4-5 mm, broadly ovate. Inflorescence a compact raceme, hemispherical, 8-9 mm long. Pedicel c. 1 mm, shorter than calyx tube. Calyx 1.5-2.0 mm, glabrous. Corolla yellow becoming yellowish brown. Vexillum 3-4 mm long.

Distribution: Throughout Europe, extending to the Caucasus; introduced in Pakistan (Murree hills, Chenab valley).

dubium: uncertain, doubtful

Annual or biennial herb, with prostrate or ascending branches, up to 30 cm long. Leaves 3-foliolate with obovate leaflets; petiolule of apical leaflet longer than those of lateral leaflets. Flowers in axillary heads, up to 20-flowered. Flowers yellow, turning yellowish-brown after flowering. Flowerheads cone-shaped after flowering, due to the deflexed old flowers.

A native of Europe and Southwest Asia.

Annual, Herbs, Taproot present, Nodules present, Stems erect or ascending, Stems or branches arching, spreading or decumbent, Stems less than 1 m tall, Stems solid, Stems or young twigs glabrous or sparsely glabrate, Stems or young twigs sparsely to densely hairy, Leaves alternate, Leaves petiolate, Stipules conspicuous, Stipules green, triangulate to lanceolate or foliaceous, Stipules persistent, Stipules clasping stem at the base, Stipules adnate to petiole, Leaves compound, Leaves pinnately 3-foliolate, Leaves odd pinnate, Leaflets dentate or denticulate, Leaflets 3, Leaves glabrous or nearly so, Inflorescences racemes, Inflorescences globose heads, capitate or subcapitate, Inflorescence axillary, Inflorescence terminal, Bracteoles present, Flowers zygomorphic, Calyx 5-lobed, Calyx glabrous, Petals separate , Corolla papilionaceous, Petals clawed, Petals orange or yellow, Banner petal narrow or oblanceolate, Wing petals narrow, oblanceolate to oblong, Wing petals auriculate, Wing tips obtuse or rounded, Keel tips obtuse or rounded, not beaked, Stamens 9-10, Stamens diadelphous, 9 united, 1 free, Filaments glabrous, Style terete, Style persistent in fruit, Fruit a legume, Fruit unilocular, Fruit indehiscent, Fruit oblong or ellipsoidal, Fruit orbicular to subglobose, Fruit or valves persistent on stem, Fruit enclosed in calyx, Fruit glabrous or glabrate, Fruit 1-seeded, Seeds cordiform, mit-shaped, notched at one end, Seed surface smooth, Seeds olive, brown, or black.

Trifolium dubium, the lesser trefoil, suckling clover, little hop clover or lesser hop trefoil, is a flowering plant in the pea and clover family Fabaceae. This species is generally accepted as the primary plant to represent the traditional Irish shamrock.

It is native to Europe, but can be found in many parts of the world as an introduced species.

It is probably an allotetraploid with 2n=32 that arose from the crossing of Trifolium campestre and T. micranthum.