Giant buttercup

Scientific name: Ranunculus acris (Updated 26 July 2017)
  • Key characteristics
  • Biology
  • Impacts
  • Control
  • Further information

  • Perennial, reaching up to 1 m tall
  • Yellow glossy flowers 15 – 25 mm across with 5 petals appearing mainly between November and April
  • A short rhizome (horizontal underground stem up to about 100 mm long) with fibrous remains of old leaves, axillary buds and fleshy roots
  • Leaves highly variable in size (can be as big as an outstretched hand), hairy, three primary lobes, highly variable lobe dissection, long hairy petioles
  • Genetically highly diverse species complex with up to 6 different chloroplast cytotypes from Europe coexisting in New Zealand dairy pastures
  • Avoided by dairy cattle due to bitter taste
  • The species is common in swamp and wasteland areas, river flats and dairy pastures in high-rainfall areas.

Origin

  • Multiple introductions from Europe (its native range)
  • Brought to New Zealand by early settlers
  • Has invaded many other countries in the Northern and Southern hemispheres including North America, South Africa, Tasmania and Australia.

Life cycle

  • Giant buttercup is a short-lived rhizomatous perennial, with individual plants flowering and producing seeds and daughter rhizomes for several years before dying
  • Seeds germinate from late autumn to late spring
  • Leaf growth peaks in late spring
  • Leafy daughter shoots are produced throughout summer and autumn as branches on the parent plant’s rhizomes, resulting in a slow outward creep of the plant and the creation of patches
  • Flowering stems die back after the seeds are shed and are replaced by the daughter shoots which overwinter as leafy rosettes
  • Seeds fall close to the parent plant and some can remain dormant in the soil for several years
  • The seeds have a small hook enabling them to attach to, and be readily spread long distances by grazing cattle and other animals
  • Other long-distance seed dispersal vectors include hay, farming equipment, roadside mowers, footwear, clothes and flood waters.

Benefits

  • Provides nectar for bees
  • Scented flowers attract and provide food for moths and many other small insects
  • In the past the plant has been used medicinally as a last resort cure for syphilis. However, safer medicines are now readily available.

Impact on pasture

  • At peak cover in late spring, a dense population of giant buttercup can occupy 50% of a pasture (Bourdôt et al. 2003) and at worst, there may be no grazing available
  • Dairy and other cattle avoid grazing the plant and its surrounding pasture thus it reduces the pasture’s stock-carrying capacity in proportion to its coverage
  • On a typical Golden Bay dairy farm with a paddock average peak cover of giant buttercup of 12%, overall farm profit is reduced by $1,040/ha or 36% (Bourdôt et al. 2012)
  • At a national scale, the value of lost milk solids production due to giant buttercup could be as high as $592 million per year (Saunders et al. 2017)
  • Resistance to herbicides that once provided adequate control has evolved in giant buttercup populations on some dairy farms, leaving these farmers with reduced options for control (Lamoureaux & Bourdôt 2007)
  • All of New Zealand is climatically suitable for giant buttercup and dairy farmers should learn how to distinguish it from the other less troublesome species of buttercup (Bourdôt et al. 2013)
  • Giant buttercup reduces the amount of clover and grass in a pasture through competition
  • Rapid increase in the amount of giant buttercup in a paddock can occur due to seedling establishment in ‘pugged’ areas in a pasture (Lusk et al. 2009).

Impact on stock

  • Protoanemonin, a toxin created during the ingestion of giant buttercup can cause blistering of the tongue and lips of cattle, ventricular fibrillation, intestinal disorders and respiratory failure
  • There are no recorded cases of stock poisoning due to giant buttercup in New Zealand

Grazing management

  • Giant buttercup may be eaten by sheep which could explain why it is never a problem in sheep-grazed pastures. Cattle will not eat the plant throughout most of the year which makes it much more of a problem on dairy farms
  • Dairy and beef cattle encourage giant buttercup by eating its competitors (e.g. grasses, clover). Overgrazing should be avoided
  • Pugging encourages giant buttercup by creating bare soil where seeds can germinate and rhizomes can invade. It should be avoided.

Grubbing / mowing of pastures

  • Mowing a pasture containing giant buttercup before it flowers (in November) can prevent seeds forming
  • If the plants are mown after flowering, seeds may be spread by the mower
  • Pre- or post-graze mowing may be effective in reducing the buttercup over the longer term, resulting in more edible dry matter in the pasture and higher paddock milk solids yields
  • Pasture growth-enhancing additives such as gibberellic acid and liquid nitrogen are unlikely to be useful alone or as additives to herbicides according to the results of Sustainable Farming Fund project SFF 401449 (2014-2017)
  • Hay made from paddock containing giant buttercup will contain the seeds of the weed and should not be fed out in buttercup-free paddocks
  • Plants can be dug out, but care is required to ensure that rhizomes are completely removed as these can easily re-sprout
  • Disposal of removed plants should be carried out carefully to prevent the ripening and dispersal of seeds.

Chemical control

  • The herbicides occurring in products with label claims for giant buttercup (Table 1) fall into 4 mode-of-action groups
  • A giant buttercup population will evolve resistance to all herbicides in a particular mode-of-action group through repeated use of one or several members of the group
  • Rotation between mode-of-action groups will delay or prevent the development of herbicide resistance
  • Mode-of-action mixtures (e.g. tank mix of MCPA + flumetsulam) may help delay the development of herbicide resistance
  • Aminopyralid + triclopyr or aminopyralid alone are the most effective herbicides for giant buttercup control (Table 1)
  • Although bentazone, MCPA, MCPB, thifensulfuron-methyl and flumetsulam are not so effective (Table 1), they provide options for herbicide mode-of-action rotation.
  • Herbicides applied in late winter/spring will be most effective
  • Check withholding periods before the use of any of these chemicals on pasture – there can be a withholding period of several weeks with some herbicides.

 

Table 1. Mode-of-action group, clover damage and efficacy of herbicides against giant buttercup in dairy pastures when applied in spring as a broadcast spray.
Herbicide 1 Mode-of-action group Clover damage? Efficacy (% reduction in giant buttercup ground cover)2
Aminopyralid O3 Yes 78
Aminopyralid + triclopyr O3 Yes 86
Bentazone + MCPB C3/01 No 39
MCPA O1 Yes 46
MCPB O1 No 33
Thifensulfuron-methyl B Yes 35
Flumetsulam B No 40

1The registered names of the herbicide products containing these active ingredients are too numerous to list here. Consult your farm advisor, industry rep or the New Zealand Agrichemical Manual for more information. Always follow the application guidelines given on the product labels.

2Data from Sustainable Farming Fund project SFF 401449 (2014-2017). The reductions in the giant buttercup ground cover are averages over assessments made 2 and 7 months after treatment (18 paddocks, 2 on each of dairy farms 1 to 9), 19 months after treatment (12 paddocks, 2 on each of farms 1 to 6) and 31 months after treatment (6 paddocks, 2 on each of farms 1 to 3). There were large differences between paddocks in the initial cover of the buttercup and considerable variation between paddocks and farms in responses to the herbicides.

Biocontrol

  • Two naturally occurring plant pathogenic fungi found on giant buttercup are known to damage the plant:
    • A species of Gnomonia, will infect the plant but not cause death
    • Sclerotinia sclerotiorum causes a soft-rot disease and death of plants. While lethal to the giant buttercup, this fungus does not damage pasture grasses and clovers
  • The use of Sclerotinia sclerotiorum as a mycoherbicide and the potential of insects as biocontrol agents are topic of current research. The fungus has not been successful in the field experiment of project SFF 401449 .
  • A classical biological programme for giant buttercup in New Zealand is not being pursued because of the complications in finding a suitably efficacious and safe agent due to the many native buttercup species and the complex genetic makeup of giant buttercup.

Bourdôt G, King W, Rennie G 2012. Giant buttercup – modelling the financial benefits of control on a Golden Bay dairy farm. Proceedings of the New Zealand Grasslands Association. Pp. 177-181.

Bourdôt GW, Saville DJ, Crone D 2003. Dairy production revenue losses in New Zealand due to giant buttercup (Ranunculus acris). New Zealand Journal of Agricultural Research 46: 295-303.

Bourdôt GW, Lamoureaux SL, Watt MS, Kriticos DJ 2013. The potential global distribution of tall buttercup (Ranunculus acris subsp. acris); Opposing effects of irrigation and climate change. Weed Science 61: 230-238.

Lamoureaux S, Bourdôt GW 2007. A review of the ecology and management of Ranunculus acris L. in pasture. Weed Research 47: 461-471.

Lusk CS, Lamoureaux SL, Bourdôt GW 2009. Giant buttercup (Ranunculus acris L.) seedling emergence and survival in Golden Bay dairy pastures. New Zealand Plant Protection 62: 222-227.

Popay I, Champion P, James T 2010. An illustrated guide to common weeds of New Zealand. New Zealand Plant Protection Society, Christchurch, New Zealand. 416 p.

Saunders J, Bourdôt G, Greer G, Saunders C, James T, Watt M, Monge J 2017. The economic costs of weeds on productive land in New Zealand. International Journal of Agricultural Sustainability 15: 380-392

Young S 2013. New Zealand Novachem agrichemical manual. Agrimedia Ltd, Christchurch, New Zealand. 767 p.