- Latin synonym: Rhinanthus serotinus
- Name also: Greater Yellow-rattle, Late-flowering Yellow Rattle (USA)
- Family: Broomrape Family – Orobanchaceae
(formerly Figwort Family – Scrophulariaceae)
- Growing form: Annual herb. Hemiparasite.
- Height: 30–50 cm (12–20 in.). Stem usually abundantly branched, sometimes branchless, 4-edged especially in upper part, with reddish brown speckles.
- Flower: Corolla zygomorphic, approx. 20 mm (0.8 in.) long, pale yellow, fused, bilabiate, long and arched tube. Upper lip hooked, flat-sided, tip with 2 purple, tapered teeth. Lower lip 3-lobed. Calyx 4-lobed, oval, wide, lime green. Stamens 4. Gynoecium fused, single-styled, body often protruding from corolla. Flowers borne in spike-like groups, terminating stem and branches.
- Leaves: Opposite, stalkless. Blade narrowly ovate–almost linear, quite blunt, densely serrated. Narrow-leaved rattle (ssp. vernalis) usually with 12–16 pairs of veins, ssp. apterus with 15–25. Subtending bracts ovate, almost yellow.
- Fruit: Brown, flat capsule inside calyx.
- Habitat: Road and ditch banks, field margins, fallow fields, seashore meadows.
- Flowering time: June–July.
Rattles’ scientific name Rhinanthus comes from the Ancient Greek words rhinos, ’nose’ and anthos, ’flower’. Rattles could easily be called ‘nose-flowers’: the flower’s upper labellum forms a hooked nose, and at the bottom of the throat there are two purple-tinged teeth. Ripening seeds remain protected inside the fruit nest. This Construction has given rise to many kinds of associations. In the old days the calyx was a purse in children’s games and the seeds that hung inside were the money. When the capsules ripen, the stems dry and become rigid, and gusts of wind can carry off the winged seeds. The rattle of the seeds in the capsule used to be the sign for farmers to begin hay-work.
As a hemiparasite, narrow-leaved rattle sucks nutrition from its neighbour’s roots at the same time as it assimilates itself though its green leaves. Narrow-leaved rattle can be divided in Finland into two variations; var. vernalis is the more common of the two in the wild, while var. apterus is casual and hard to find.