Natural England Technical Information Note TIN060 The use of yellow rattle to facilitate grassland diversification In the last sixty years England has lost most of its species-rich semi-natural grassland. Increasing the numbers and species of native wild flowers in semi- improved grassland (ie grassland that has undergone some agricultural improvement) can go some way to restoring this valuable habitat. This note gives advice on how yellow rattle Rhinanthus minor can help other wild flower species establish in semi- improved grasslands, particularly in grasslands being managed under Environmental Stewardship. Other notes on enhancing and recreating semi-natural grasslands are available and details can be seen below. Environmental Stewardship is an agri- Yellow rattle - ecology environment scheme that provides funding to Yellow rattle is an annual wildflower that obtains farmers and other land managers in England. A some nourishment by parasitizing its host but key option in the Environmental Stewardship also photosynthesizes, the term for this is Higher Level Stewardship Scheme is the hemiparasitic. restoration of species-rich, semi-natural grassland (HK7) normally from semi-improved swards. The botanical diversity of such grassland may be enhanced by simply amending management practices, for example changing the timing and intensity of grazing. However, on sites where the potential for natural regeneration and re- colonisation of desirable plant species is judged to be low, then pro-active restoration will be required. This will involve the introduction of seeds and the creation of gaps in the sward to allow them to establish. Seeds can be introduced by over sowing, slot seeding or the spreading of green hay. Yellow rattle is often a component of seed mixtures and of green hay, but on some sites there are good reasons for specifically establishing yellow rattle before sowing other wildflower species as it can help improve the chances of the other species Yellow rattle eventually establishing. First edition 12 November 2009 www.naturalengland.org.uk Natural England Technical Information Note TIN060 The use of yellow rattle to facilitate grassland diversification Yellow rattle is native to the UK and can be However, it is not clear yet how this might impact found in a wide range of grassland habitats. It is vegetation community composition and particularly associated with semi-natural development. species-rich neutral hay meadows especially National Vegetation types: Establishing yellow rattle before other wildflower species are introduced is particularly suited to northern hay meadows (MG3); situations where either: flood meadows (MG4); lowland hay meadows (MG5); and The soil is at the higher end of the recommended range for phosphorus ie soils water meadows (MG8). with a P Index of 2. For further information see Technical Information Note 061 - Sward It can occur on a wide range of soil types but is enhancement: Selection of suitable sites. Or normally absent from sites with a pH less than 5.0. The vegetation of the site, while fulfilling the targeting criteria, has a significant cover of It lacks a long term persistent soil seed bank and competitive species such as perennial rye- is dependent on annual establishment from seed grass, Yorkshire fog and white clover and/or is produced the previous year. very productive. Seeds generally germinate in spring (February- On sites that are identified as being suitable for April depending on altitude) after a period of species rich grassland restoration (see site chilling to break dormancy. It flowers from early selection below) it should not be necessary to May onwards and most plants will have set seed establish yellow rattle before other wildflower by early July in the lowlands and by mid to late species. July in upland areas. Target vegetation type Yellow rattle has a limited dispersal but The use of yellow rattle will be most appropriate distances can be increased through the hay where the target vegetation types for restoration making process. The viability of seed decreases are species-rich neutral grassland conforming to rapidly with storage. the NVC types mentioned above ie MG3, MG4, MG5 and possibly MG8. It parasitizes a wide range of grass and wildflower species but performs particularly well It may also be feasible to use yellow rattle where on grasses and legumes. Consequently, it has the aim is to restore species-rich calcareous the potential to reduce the vigour and biomass of pasture (see section on subsequent its hosts and hence overall grassland sward management) but only where it is practical to productivity. have a temporary period of cutting management to ensure the yellow rattle establishes. Grazing Use of yellow rattle as a practical can be done in late summer after the yellow management tool for grassland rattle has seeded. diversification The presence of yellow rattle in grassland Site selection should reduce the biomass of the dominant Technical Information Note TIN061 - Sward grass species. This should reduce competition enhancement: Selection of suitable sites, and and allow wildflower species an opportunity to the key in the FEP feature manual (Natural become established. England 2008) (botanical enhancement potential of species-poor grassland) provide guidance on There is increasing evidence that yellow rattle the selection of suitable sites for restoring to also effects below-ground soil processes such species-rich, semi-natural grassland. Following as the rate of nitrogen cycling and the this guidance should ensure highly productive composition of the soil microbial community. Page 2 Natural England Technical Information Note TIN060 The use of yellow rattle to facilitate grassland diversification existing swards are not targeted as these are not It will also result in other wildflower species likely to succeed. being introduced simultaneously, although there is no reason why this should be a problem. Yellow rattle may fail to establish in very productive, intensively managed grassland Seed should be broadcast over the sward swards due to its failure to compete with surface late summer /early autumn using, for established competitive species such as example, a fertiliser spreader or a seed drill with perennial rye-grass (Lolium perenne). the coulters lifted up (see Technical Information Note TIN064 - Sward enhancement: diversifying Site preparation grassland by over sowing and slot seeding). This Before introducing yellow rattle seed in late should be followed by cattle grazing to press the summer/early autumn create a short sward with seed into the soil. If cattle are unavailable, then frequent patches of bare ground at least 10cm in a flat, light roller should be used. diameter (see also Technical Information Note TIN064 - Sward enhancement: diversifying It is vital that fresh seed (produced in the same grassland by over sowing and slot seeding). season it is sown) from a reliable supplier is used. This can be done by cattle grazing (the hoof and tooth method) or, if livestock are unavailable, by On sites that are next to an SSSI or an existing using mechanical means such as a power species-rich semi-natural grassland, the seed harrow or a set of discs. ) should be of local origin. Elsewhere it should be of British origin as per the guidance provided in Evidence from restoration of upland hay Technical Information Note TIN038 - Seed meadows in the North Pennines suggests that sources for grassland restoration and re-creation using machinery is a more practical option. in Environmental Stewardship. Seeding For advice on introducing yellow rattle via green The recommended sowing rate for yellow rattle hay see Technical Information Note TIN063 - is between 0.5 - 2.5 kg per ha with the target of Sward enhancement: diversifying grassland by establishing a density of between 100 to 200 spreading species-rich green hay. yellow rattle plants per m2 . At this density there should be a significant reduction in the Subsequent management competitiveness and productivity of the sward. Allow yellow rattle to set seed by a taking a late hay cut (from early July to late July depending A general guide is that the greater the on altitude) followed by aftermath grazing. Fields productivity of the sward, the higher the sowing normally managed as pastures should be density required. Higher seeding rates of 30 kg managed as hay meadows during the initial per ha (1000 seeds/m2) have been advocated to establishment phase. ensure successful establishment (see Westbury and others 2006) but cost would preclude using Once yellow rattle has reached the desired density of between 100 and 200 yellow rattle this rate except possibly on small sites. In 2009 2 the cost of yellow rattle seed was around £190 plants per m additional wildflower species can per kilogram. be introduced. The time taken to reach the desired density will depend on a number of Alternatively, yellow rattle can be introduced via factors, including the initial seed rate, but is likely green hay from a donor site which has a to be at least 2-3 years. significant concentration of yellow rattle. The disadvantage of this is that it can be difficult to Advice on introducing wildflower species by over achieve the required seeding rate as a high sowing/hay spreading can be found in Technical proportion of seed will be lost during harvesting. Information Note TIN064 - Sward enhancement: diversifying grassland by over sowing and slot seeding and Technical Information Note 063 - Page 3 Natural England Technical Information Note TIN060 The use of yellow rattle to facilitate grassland diversification Sward enhancement: diversifying grassland by Technical Information Note TIN065 Sward spreading species-rich green hay. enhancement: diversifying grassland using pot-grown wildflowers or seedling plugs In the years following the sowing of additional Technical Information Note TIN038 Seed species continue to manage the site as a hay sources for grassland restoration and re- meadow. This will help maintain a high density creation in Environmental Stewardship of yellow rattle.