Perennial knawel (Scleranthus perennis prostratus)

loading
Perennial knawel in flower
loading
Loading more images and videos...

Perennial knawel fact file

Perennial knawel description

KingdomPlantae
PhylumAnthophyta
ClassMagnoliopsida
OrderCaryophyllales
FamilyCaryophyllaceae
GenusScleranthus

This subspecies of the perennial knawel is a small, inconspicuous and prostrate plant. It has brittle, woody stems and the five sepals have prominent white borders. The small flowers appear between June to September.

Size
Height: Up to 20 cm
Top

Perennial knawel biology

In spite of the name perennial knawel usually behaves as a biennial plant, living for two years. The Breckland subspecies is thought to flower all year round on occasions but usually flowers during the summer months.

Top

Perennial knawel range

This subspecies is found only in the Breckland region of East Anglia although it has been recorded on six other sites outside Breckland, all in Norfolk. The nominate race, Scleranthus perennis perennis is widespread throughout central and southern Europe and the range extends into north-west Europe where it is in decline. Britain represents its furthest north-western outpost where it is known from only one single site in mid-Wales.

Top

Perennial knawel habitat

Prefers the open, sandy, acidic soils characteristic of the Brecks. Breckland is an area where average annual rainfall is low and the soils are free-draining and of poor quality. The prostratus subspecies of perennial knawel is associated with uncompacted tracks and close-cropped grassland. Being a poor competitor it requires open soil for germination.

Top

Perennial knawel status

Classified as Endangered in the UK.

Top

Perennial knawel threats

Neither of the two subspecies of perennial knawel have been historically plentiful in Britain. The Breckland subspecies has only been recorded from 25 sites, and never more than six at any one time. The survival of the plant has also been threatened by loss of habitat. During the 20th century, much of the Breck has been lost to afforestation, agricultural improvement and development. In addition, traditional grazing by sheep and rabbits has fluctuated through declining stock values and the effects of myxomatosis on rabbit numbers. Many of the perennial knawel's former sites have become unfavourable for it through an increase in more dominant vegetation and encroachment of gorse and Scots pine seedlings.

Top

Perennial knawel conservation

Scleranthus perennis ssp. prostratus has been included in English Nature's Species Recovery Programme. In 1996, Yvonne Leonard, a botanist living in the East Anglian Brecks, produced a Species Action Plan for this subspecies. The objectives were to reinstate viable populations of the plant on at least three of its former sites. This involved a study of the plant to ascertain its requirements and to assess the suitability of former site for a re-introduction programme. In partnership with local landowners, the two local county trusts, local authorities and the Royal Botanic Gardens, Kew, plants were germinated and a 'nursery' set up to supply plants for re-introduction. Some 11 plots were chosen and regular monitoring has taken place to establish whether conditions and management were suiting the plants. There has been some success with these re-introductions but it is still too early to say that the perennial knawel has been preserved as a naturally occurring species. With much of the trial area within a large, privately owned farm, maintaining the ideal conditions for the plant relies heavily of the co-operation of the landowner and the management by farm contractors.

The UK Biodiversity Action Plan for this species is available at UK BAP.
Top

Authentication

Information supplied by English Nature.

http://www.english-nature.org.uk

Top

Glossary

Biennial
A plant that lives for two years and typically flowers only in the second year.
Myxomatosis
A contagious viral disease in rabbits.
Prostrate
In plants, growing along or close to the ground.
Subspecies
A different race of a species, which is geographically separated from other populations of that species.
Top

References

X
Close

Image credit

Perennial knawel in flower  
Perennial knawel in flower

© Bill Meek / CEH Monks Wood

Bill Meek
Tel: +44 (0) 1487 772 400
wrm@ceh.ac.uk

X
Close

Link to this photo

ARKive species - Perennial knawel (Scleranthus perennis prostratus) Embed this ARKive thumbnail link ("portlet") by copying and pasting the code below.

Terms of Use - The displayed portlet may be used as a link from your website to ARKive's online content for private, scientific, conservation or educational purposes only. It may NOT be used within Apps.

Read more about

X
Close

MyARKive

MyARKive offers the scrapbook feature to signed-up members, allowing you to organize your favourite ARKive images and videos and share them with friends.

Play the Team WILD game:

Team WILD, an elite squadron of science superheroes, needs your help! Your mission: protect and conserve the planet’s species and habitats from destruction.

Conservation in Action

Which species are on the road to recovery? Find out now »

Help us share the wonders of the natural world. Donate today!

Blog