Claviceps purpurea

Claviceps purpurea grows on grasses and cereal crops, producing purplish-black, hard, horn-shaped 'ergots' or sclerotia which replace the seed or grain in the flowerhead.  The sclerotium overwinters on the soil and small pinkish-brown fertile heads on violet stems arise in Spring, releasing ascospores in time to infect new grass flowerheads.

There are other species of Claviceps producing ergots on some species of grass or on Spike-rush.  Ustilago avenae causes 'Loose Smut of Oats' on species such as False Oat-grass; the grains are a mass of fine powdery purple-black spores which are  readily dispersed. 

The sclerotia of Claviceps purpurea are said to sink in water.   The sclerotia of Claviceps found on grasses such as Phalaris arundinacea (Reed Canary-grass), Calamagrostis (Wood small-reeds) and Deschampsia caespitosa (Tufted Hair-grass) are said to float - an adaption to their moist or humid environment.   Some authorities consider this to be a variety of Claviceps purpurea (var. phalaridis) and others have given it the specific name Claviceps humidiphila - see 'Further information' below)

Field photos.  It is important to note the host species of grass.  Please submit your record as 'Claviceps purpurea' and not as the variety 'var. purpurea'

Grasslands and grain crops; species commonly affected include Lolium perenne (Perennial Rye-grass), Arrhenatherum elatius (False Oat-grass), Dactylis glomerata (Cocksfoot), Holcus lanatus (Yorkshire Fog), Elymus and Elytrigia spp. (Couch-grasses), Phleum spp. (Timothy), etc. and many other species.   

July to November

The ergots contain poisonous alkaloids.  When eaten by humans or animals in infected grain, it causes ergotism or St. Anthony's Fire.  Symptoms include gangrene, hallucinations and convulsions.  In the past, infected grain has caused mass poisoning of whole villages, etc.  

Taxonomy is unclear.  In the past Claviceps purpurea had several named varieties, with Claviceps purpurea var. purpurea being the species usually referred to as 'Ergot' and commonly found on Rye-grasses, etc.  The status of this varietal name is unclear, and we therefore recommend that records are submitted as the species, not the variety, and that the grass host is identifed and noted.

See Plant Parasites of Europe website and Pažoutová, S. et al (2015) Delimitation of cryptic species inside Claviceps purpurea.  Fungal Biology 119.1, 7-26, available via Science Direct