Rhinanthus minor, known as yellow rattle, is a herbaceous wildflower in the genus Rhinanthus in the broomrape family. It has circumpolar distribution in Europe, Russia, western Asia, and northern North America. An annual plant, yellow rattle grows up to tall, with upright stems and opposite, simple leaves. The fruit is a dry capsule, with loose, rattling seeds.
The preferred habitat of Rhinanthus minor is dry fields or meadows; it tolerates a wide range of soil types. It flowers in the summer between May and September. It is parasitic plant, notably on Poaceae (grasses) and Fabaceae (legumes), and farmers consider it to be a pest, as it reduces grass growth.
Yellow rattle is used to create or restore wildflower meadows, where it maintains species diversity by suppressing dominant grasses and the recycling of soil nutrients. The seed is sown thinly onto grassland from August to November—to germinate the following spring, the seeds need to remain in the soil throughout the winter months.
Description
The leaves are sessile (they grow directly from the stem), somewhat heart-shaped at the base, otherwise ovate (oval-shaped) to lanceolate (shaped like a lance tip), dentate (toothed) and scabrid (a little rough to the touch). The stem, which stands upright, can be simple or branched, is four-angled and often streaked or spotted black.
The yellow flowers are across and have a straight tube for the petals. The silvery-coloured fruit is a dry capsule, which contains loose, rattling seeds when ripe that give the plant one of its common names.
The herbalist Nicholas Culpeper, in his The English Physician (first published in 1652), wrote of yellow rattle as being "good for cough, or dimness of sight". The plant has a reputation of being toxic to animals. The seeds contain which cause them to have a bitter taste.
Taxonomy
According to Plants of the World Online it has four accepted subspecies:
- Rhinanthus minor subsp. calcareus – Endemic to Great Britain
- Rhinanthus minor subsp. lintonii – Endemic to Great Britain
- Rhinanthus minor subsp. minor – Native to Europe and western Asia, introduced widely
- Rhinanthus minor subsp. monticola – France, Great Britain, and Ireland
The synonyms of Rhinanthus minor and its four subspecies include 50 species names.
Distribution and ecology
Yellow rattle is an annual wildflower. It is parasitic plant, in that it can gain its nutrients by penetrating the roots of neighbouring green plants with its own roots, but is a facultative parasite, in that it acts opportunistically when in contact with a root. The hemiparasitic nature of yellow rattle can result in stunted, unbranched individual specimens. The plant can associate with many different host species, notably Poaceae (grasses) and Fabaceae (legumes).
In Ireland and Scotland, yellow rattle is often associated with Machair habitat, which consists of coastal grassland. The seeds are spread effectively by traditional hay-making practices. Farmers seek to remove it since it affects yields by weakening grass; it is an indicator of poor grassland.
Effects on plant community structure
Research, including that at the UK's Centre for Ecology and Hydrology, has shown that encouraging it to grow in hay meadows greatly increases biodiversity, by restricting grass growth and thereby allowing other species to thrive. As of 2021 a majority of studies had found positive or neutral effects of the introduction of Rhinanthus spp. on grassland species richness and diversity, with most finding a negative effect on grasses.
Conservation status
Being an annual, it is not found in regularly mown or grazed grassland where the seeds are not provided with an opportunity to spread over the ground. The lack of a seed bank for yellow rattle means that it depends on seed produced from plants during the previous year.
Pasture and hay field infestation
Uses and cultivation
The yellow rattle seed is sown thinly onto grassland where gaps have been created, or where all the grass has been cut back and the clippings removed. Seeds can be also be introduced by the spreading of green hay. The grass should be kept short until the beginning of March, after which the seedlings become established.
After the yellow rattle plants have Germination and matured, the fruits shed their seeds. The meadow hay is cut and removed to encourage the growth introduced wild flowers. The seed, which is short-lived, is sown in the autumn, using seed harvested that year. The seeds have to remain on or under the ground throughout the cold months of winter in order to germinate in the spring.
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