Essex Biodiversity Project
Sea Hog's Fennel
Identification - Sea Hog's Fennel (Peucedanum officinale) is an exclusive coastal grassland umbelifer (Umbrella shaped) plant growing to a height of around 2 metres. It is robust and hairless and the leaves are 4 - 6 times trifoliate (like hands) with flat narrow untoothed leaflets (small leaves making up a big leaf) 4 - 10 cm long. The umbels (flowers) are up to 20 cm across and are sulphur yellow. The stems are solid and sometimes slightly angled, are pale yellow-green or red-purple. (Rose 1981)
(Photo - Zoe Ringwood)
General ecology - Sea Hog's fennel grows from the highest level salt marshes up to 1km from saline water indicating that it is very salt tolerant. It also grows on seawalls and associated grassland. 60% of the national population occurs in Essex and is only present in North East Essex. It is the main food plant for another Essex Biodiversity Action Plan species - Fisher's estuarine moth (Gortyna borelii lunata). Together the two species plans make a significant contribution to conservation of the seawall communities.
Sea Hog's Fennel is a long-living umbellifer that can grow to over 2 m in height. In Britain, the distribution of the plant is restricted to two main localities: northeast Essex around the Walton Backwaters area and the north Kent coast between Faversham and Reculver. In these areas the plant generally grows within species-poor coastal grassland habitats that are threatened by rising sea levels and scrub encroachment.
The plant is not tolerant of high levels of soil salinity and therefore will not survive in areas that are inundated by the sea. In mainland Europe the plant is not coastal and grows within a diversity of grassland habitats and at altitudes of up to 1800 m.
In addition to being of conservation priority itself, two rare species of moth, Fisher’s Estuarine Moth (Gortyna borelii lunata) and Agonopterix putridella (a micro-moth), are completely reliant on Hog’s Fennel as their sole caterpillar food plant. Work being conducted to conserve Fisher's Estuarine Moth (see our web page) on a landscape-scale is directly benefiting Hog’s Fennel.
Surveying tips - The plant is currently being monitored by professional ecologists.
Project Work - Essex Biodiversity Project has been working with Dr Zoe Ringwood of Writtle College to ensure that Sea Hogs Fennel and Fisher’s estuarine moth will continue to thrive on the Essex coast.
Work is continuing on Skippers Island, off Thorpe-le-Soken, an Essex Wildlife Trust Reserve, the key site for both the plant and moth. The work includes clearing scrub so that space is created for Sea Hogs Fennel to expand into the centre of the island away from the sea. The plant has been introduced and established to Abbots Hall Farm as part of the joint project with Fishers Estuarine Moth.
Progress report on research trials to establish Sea Hog's Fennel
Download the full report (PDF 212KB)