Rhinanthus minor, commonly known as Yellow Rattle is an attractive wildflower of grasslands. Growing to around 30cm (12in) tall, with leaves with a serrated margin, it has pretty two lipped flowers, the upper lip with two white or purple ‘teeth’. Behind the flower the joined sepals inflate to form a green bladder sometimes tinged with red. Flowering occurs from May through to September followed by a seed capsule which rattles within the now brown and papery bladder. The majority of seed ripens in mid to late July and the rattling of the fruit within the bladder was said to indicate that the meadow was ready to be cut for hay, hence its other common name of hay rattle.
Yellow rattle is found in moderate to low fertility grasslands particularly meadows but also roadsides, dunes, lightly grazed pastures and dry areas within fens. It is partially parasitic, parasitizing the roots of a wide range of meadow plants especially grasses and legumes and whilst capable of carrying out its own photosynthesis it is dependent upon these hosts for additional supplies of carbohydrates and minerals. By drawing nutrients from surrounding vegetation it impedes their growth and helps maintain an open sward structure.
Yellow rattle seed must be sown in the autumn as it needs prolonged chilling through the winter to trigger its germination the following spring. The seed should be scattered onto the prepared surface at a rate of 0.1 to 1 g/m2.
In the past this plant was a serious pest for farmers as it weakens grasses and as a result could reduce hay yields by as much as 50%. In a landscape or garden context however, this suppression of grass growth is welcomed. Once established, Yellow Rattle can reduce the competitive vigour of certain grasses by up to 50%, thus benefiting other sown wildflowers. It produces a better display of flowers and eases the mowing required.
Yellow rattle germinates late February to early March, flowers in June, and sets seed in July. At the end of each growing season as the annual yellow rattle plants die away they leave behind gaps into which new wild flowers can establish.
Using yellow rattle to increase species diversity:
Yellow rattle may be sown as a component of meadow mixtures on to a prepared seedbed. Seed can also be added to a newly established meadow after its first season.
First year meadow management (mowing) can compromise seed set of yellow rattle. To be sure of getting yellow rattle in the second year, it is best to re-sow yellow rattle in the autumn of the first year. Where cornfield annuals have been sown as a ‘nurse crop', yellow rattle has more opportunity to self-seed.
Yellow rattle establishment can be unpredictable and plant numbers may take two to three years to build up, this will depend upon the sowing rate chosen, and site conditions.
For good results, the following points are essential:
Yellow rattle will parasitize many species, not just grasses. It would appear to be opportunistic in selecting the more vigorous components of a sward which is often the grasses and clovers. However, Yellow rattle will not thrive in all grassland. The most suitable sites will be managed grassland of low to medium fertility that contains a balanced sward of finer grasses not dominated by coarse or vigorous grass (ryegrass, cocksfoot, tall oat-grass or couch).
Yellow rattle is intolerant of shade and on fertile sites where coarse grasses are present or on grasslands that are never cut or grazed it tends to get shaded out.
Grassland that is the result of sowing a meadow mixture will have suitable grasses, as will finer turf in gardens and meadows. Yellow rattle often fails to take in ryegrass leys and neglected, over-grown or tussocky grassland.
Cut or graze the sward in the autumn, aim to keep the grass short, around 4 to 5cm (1½ to 2in). Graze or mow before and after seeding as needed.
Create gaps across the site with exposed soil for yellow rattle seed to germinate in. This can be achieved by autumn/winter grazing with stock (their hooves open the sward), or mechanically by harrowing or raking, aiming to expose up to 50% bare soil.
Sowing: August to December
Traditional meadow management based around a late July hay cut provides Yellow rattle the best opportunity to set seed, and for its seed to scatter during the process of hay-making. The seed, which is set from late June onward, is winged and dispersed a short distance by the wind and germinates in early spring to following year.
Yellow rattle seed must be sown in the autumn as it needs prolonged period of chilling through the winter to trigger its germination the following spring. It can be sown onto the prepared surface at a rate of between 0.1g and 1g per square metre. The rate chosen is most usually a compromise between the desire to rapidly attain a plant population density sufficient to suppress grass and the available budget.
Managing swards for Yellow Rattle:
Yellow rattle is an annual with short lived seed which needs a chance to set seed each year. Autumn grazing, or mowing and harrowing each year will help to keep the sward open. This is important in providing new sites in to which yellow rattle can establish the following spring. Yellow rattle populations tend to fluctuate in meadows and often ‘move' about from year to year as a reflection of the balance of health of the yellow rattle plants and their host plants in any one patch.
Traditional meadow management based around a late July hay cut provides yellow rattle with the opportunity to set seed and for the seed to scatter during the process of hay-making. Cutting or grazing between April and mid July will eliminate yellow rattle by preventing it seeding and should be avoided.
Concern is sometimes expressed that very successful yellow rattle populations can have a negative effect on the composition of a meadow. Our advice is that as with most semi-natural grassland communities containing yellow rattle a balanced equilibrium will usually establish itself over time. There is no persistent seed bank in the soil. If deemed necessary however, yellow rattle can be reduced or eliminated by mowing to prevent seeding for one season.
Rhinanthus minor is a flowering plant in the family Orobanchaceae, native to Europe and Western Asia. Found in moderate to low fertility grasslands particularly meadows but also roadsides, dunes, lightly grazed pastures and dry areas within fens.
Rhinanthus was named after the projecting beak of the upper portion of the corolla. It is derived from two Greek words, the Greek term for nose is rhinos. (which is why a nose job is called rhinoplasty) and anthus meaning 'flower'.
He species name minor means 'smaller' or 'lesser'.
Commonly called Yellow Rattle, and occasionally Little Yellow Rattle, the rattling of the fruit within the bladder was said to indicate that the meadow was ready to be cut for hay, hence its other common name of Hay Rattle.
It is also known as Cocks Comb or Cockscomb (spelling variations abound)
Anatomically, a comb is a fleshy growth, caruncle, or crest on the top of the head of gallinaceous birds, most notably turkeys, pheasants, and domestic chickens. Its alternative name cockscomb is because combs are generally larger on males than on females - a male gallinaceous bird is called a cock.
Because of its bright colour and distinctive shape, 'cockscomb' also describes various plants, including the florists' plant Celosia cristata, Yellow rattle, Sainfoin, Wild poppy, Lousewort, Erythronium and Erythrina crista-galli.
- Additional Information
Seed Form Natural Seeds per gram Approx 300 Seeds per gram Family Orobanchaceae Genus Rhinanthus Species minor Common Name Hay Rattle
Wildflower of Britain and Ireland
Other Common Names Cocks Comb or Cockscomb Other Language Names IR - Gliográn Hardiness Hardy Annual Flowers Yellow with a white or purple 'teeth' Natural Flower Time May to September Height 15 to 50cm (6 to 20in) tall Position Intolerant of shade Soil Most suitable in low to medium fertility soil. Time to Sow Seed must be sown in the autumn as it needs prolonged chilling through the winter to trigger its germination the following spring Coverage Seed should be scattered onto the prepared surface at a rate of 0.1 to 1 g/m2.