Thesium humifusum

Tracheophyta MagnoliopsidaSantalaceaeThesiumThesium humifusum

Ecology

A perennial, with prostrate herbaceous shoots from a woody rootstock, which is hemiparasitic on the roots of various herbs. It is found in short, usually grazed, species-rich calcareous grassland, chiefly on chalk, less frequently on limestone, and rarely on clays or calcareous sandy soils near the coast. Little is known of its reproductive biology. Lowland.

Status

Native

World Distribution

Oceanic Temperate element.

© G. Toone, IWNHAS

Broad Habitats

Calcareous grassland (includes lowland and montane types)

Light (Ellenberg): 8

Moisture (Ellenberg): 3

Reaction (Ellenberg): 8

Nitrogen (Ellenberg): 3

0

Salt Tolerance (Ellenberg): 0

January Mean Temperature (Celsius): 3.8

July Mean Temperature (Celsius): 16.2

Annual Precipitation (mm): 762

Life form information

Height (cm): 20

Perennation - primary

Perennial

Life Form - primary

Chamaephyte

Woodiness

Herbaceous

Clonality - primary

Little or no vegetative spread

Count of 10km squares in Great Britain: 145

Count of 10km squares in Ireland: 0

Count of 10km squares in the Channel Isles: 6

Atlas Change Index: -0.21

Distribution information

JNCC Designations

NBNSYS0000003625

Scarce Atlas Account

Scarce Atlas Account: 

Thesium humifusum DC.

Bastard-toadflax

Status: scarce

 

This plant is found in short, species-rich calcicolous grassland, chiefly on chalk, less frequently on oolitic limestone and rarely on calcareous sandy soils near the coast. In Wiltshire, it is usually associated with Carex humilis and is mostly confined to warm, south­west facing slopes. On the oolitic limestone, at sites such as Barnsley Warren, it grows in association with Pulsatilla vulgaris and Polygala calcarea. On the Isle of Portland it grows on rather bare, shallow clayey soils overlying limestone. 

T. humifusum is a perennial hemiparasitic herb having haustoria on its roots by means of which it attaches itself to the roots of other plants. The mature plant has a woody rootstock from which in May it produces slender, yellowish-green shoots with a prostrate habit of growth. The plant is probably long-lived. It flowers freely from June onwards and produces a small ovoid fruit, but little is known concerning the fate of the seeds and conditions required for germination.

Locally, it may be relatively abundant with cover values of up to 30%, but it is easily overlooked and probably under-recorded. It has been lost from some of its former localities as a result of ploughing of down land and is also threatened by application of inorganic fertilisers and by scrub encroachment.

It is confined to western Europe (Belgium, France, Great Britain, Netherlands and Spain) and has a distinctly southern oceanic distribution (Jalas & Suominen 1976).

 

T. C. E. Wells

PLANTATT - Attributes of British and Irish plants. (.zip 1455KB) This dataset was compiled and published in 2004, and last updated in November 2008. Download includes an Excel spreadsheet of the attributes, and a PDF explaining the background and nomenclature. Note that the PDF version is the booklet as published, whereas the Excel spreadsheet incorporates subsequent corrections. A hardcopy can be purchased from the Centre for Ecology and Hydrology.

Atlas text references

Atlas (152b)
Jalas & Suominen (1976)
Stewart A, Pearman DA, Preston CD
1994.  Scarce plants in Britain.