weed policy

A Policy For Injurious "Weeds"

The Knepp Estate July 2009

2008 was the “year of the ragwort”.  It was so abundant everywhere, not just at Knepp, that it sparked considerable debate. We carried out our own research in an effort to dispel some of the myths that surround the plant and allay the fears of some of our neighbours, and decided to set up a policy to ensure that our Wildland Project stays on the right side of the Weeds Act 1959, whilst allowing this valuable wildflower to behave naturally in areas away from boundaries. 

Did you know for example that at least 30 species of insects and other invertebrates are totally dependent on Ragwort as their food Click on Buglife website.

The policy was prepared by Theresa Greenaway following consultation with our Steering Group, a voluntary but informed group of eminent scientists and land managers.

Frequently Asked Questions FAQ

See the Ragwort Monitoring 2011 report (4 MB)


Policy for Injurious Weed Control on Knepp Castle Estate.

By Theresa Greenaway,  21st October 2008

Knepp Wildland Project The Knepp Wildland Project has been underway since 2001. Most of the Estate, previously intensively farmed, has been taken out of arable production in stages since 2001. The reasons behind the decision to abandon intensive farming in favour of re-wilding are given in depth in the Knepp Castle website. The land is now grazed by low numbers of longhorn cattle, Exmoor ponies, fallow deer and Tamworth pigs. 

Land that suddenly ceases to be under an arable crop is susceptible to a proliferation of plants that quickly colonise bare soil. Five of these are considered to have such a high nuisance value that they have been specified under the Weeds Act, 1959, and at least three of these have increased in abundance on some of the land within the Knepp wildland project, which has been a cause of concern to neighbours. This resulted in representation being made to the estate by Shipley Parish Council in 2008. 

The estate has no wish for its wildland project to have a negative impact on neighbouring land interests. We have therefore drawn up and implemented a weed control policy to reassure those who are unhappy with the level of nuisance weeds that at the same time will not compromise the rationale behind its own aims for the land.

Injurious weeds The five plants specified under the Weeds Act, 1959 are common ragwort Senecio jacobaea, spear thistle Cirsium vulgare, creeping or field thistle Cirsium repens, broad-leaved dock Rumex obtusifolius and curled dock Rumex crispus. All these species are present on Knepp, but it is ragwort and to a lesser extent creeping thistle and dock that are most problematic. The control of weeds of disturbed ground is extremely difficult, even with the use of herbicides in some cases. Airborne seeds of species such as thistles and ragwort need only small patches of bare land on which to germinate successfully.  

The Injurious Weeds Act does not make it an offence for any of these five species to be present on land, but is primarily concerned with their control and prevention of spread. This document presents the Knepp Castle Estate Injurious Weed Control policy. It deals in greatest depth with ragwort, as this is known to be highly toxic to livestock.

Ragwort Common ragwort Senecio jacobaea is a native wild plant of the UK. It is also native to the rest of Europe as far a southern Scandinavia and reaches across to Western Asia and North America. It flourishes best on dry, bare or disturbed chalky or limy soils and grasslands although will grow on more acid soil. It fares least well on wetlands, scrub, woodlands including plantations, hedgerows and anywhere generally on acid soils. Ragwort forms a rosette of leaves and a taller flower stem that on average is 30-90cm. This means some plants will be smaller, but some will also be much taller when in ideal conditions. When in flower it is highly conspicuous. 

There are some seven other native species of ragwort Senecio spp., and about eleven other introductions that have either escaped from gardens or from sources such as wool shoddy.  Three of the native species are more familiarly known as groundsels. Some of the native species are extremely rare and protected or they have very limited distribution. Most of the introductions are also very limited in their distribution.  

In Sussex, excluding the groundsels, only two native species of ragwort and one introduction are likely to be encountered to any extent. Common ragwort is by far the most widespread and abundant of these; hoary ragwort Senecio erucifolius is also fairly frequent and dose occur on Knepp and the wider countryside in field margins, verges and other grasslands, although it prefers base-rich soils. Marsh ragwort Senecio aquaticus may grow on marshy ground near rivers and streams. The introduced Oxford ragwort Senecio squalidus grows on waste ground, walls, railway embankments and similar places. Although other species of ragwort – and common groundsel Senecio vulgaris – do contain similar alkaloids to common ragwort, these species are seldom present in sufficient quantity to constitute a threat to livestock.

Seed Distribution

The number of seeds produced per plant ranges widely, up to 30,000 per plant is cited by some authorities. Many plants will produce far less than this, especially as a variety of insects eat flowers and seeds; and some will produce more. Most, but actually not all, of these seeds have a hairy ‘parachute’ and are thus dispersed by wind. Most ragwort seeds, a figure of 60% has been calculated, fall around the base of the plant, and seedfall decreases with distance such that at about 36m (120ft), 0.005% seedfall occurs. This means that for a plant that does produce 30,000 healthy seeds, 18,000 land at the base of the plant; 11,700 seeds land 4.5m (15ft) away and so on until at a distance of about 36m (120ft), 1.5 seeds land. 

Ragwort is one of a large number of European plants that contain distasteful, toxic compounds in order to deter herbivores from eating them. The chemicals contained by ragwort are known as pyrrolizidine alkaloids. These are highly toxic to many mammals including livestock and humans, but are especially poisonous to horses and cattle, either fresh or in hay.  However, animals including horses, cattle and their ancestors have lived alongside ragwort in Europe, Asia and Africa for many thousands of years. The weblink Ragwort Facts http://www.ragwortfacts.com/index.htm gives further information on pyrrolizidine alkaloids and the plants that contain them. 

It is difficult to be definitive about numbers of seed, the spread of ragwort, and the number of livestock fatalities it causes. Those who call for ragwort to be eradicated will tend to cite the highest seed numbers, rate of spread, number of horses killed per annum and so on, and those who view ragwort as a valuable component of a native flora will tend to cite the lowest. To try to put ragwort into some kind of reasonable context, it is only one of a considerable number of plants that can cause horse and other livestock fatalities if consumed. In southern England, these include some common species such as foxglove, ramsoms, daffodil, cuckoo pint, ivy, white bryony, bracken, black bryony, elder, spindle and of course yew. Others, including bluebell, have also been known to poison horses although not fatally. 

Knepp Castle Estate Policy for control of spread of ragwort and other injurious weeds. 

  • As a precaution, all land adjacent to the Knepp Wildland Project boundary will be treated as though it were used for pasture or forage production, including private gardens.
  • The strip of land to a depth of about 50m around the perimeter of the wildland area and around any tenanted or privately owned land embedded within the project area but not part of it (see map) will thus, if ragwort is present, constitute the High Risk Zone identified in the Defra Code of Practice.
  • This c50m strip of land will be topped as necessary to prevent the spread by seeds of ragwort and other injurious weeds to reduce as far as practicably possible the presence of ragwort and other injurious weeds and to prevent their spread onto neighbouring land. 
  • Land 50-100m inside the Knepp boundary, if ragwort is present, will be in the Medium risk category, and as such should never change from Medium to High because it is always going to be over 50m from land used as pasture or forage production outside the Wildland Project area.
  • Land over 100m from the boundary will be in the Low risk category and should remain thus even if ragwort does occur at some density.
  • The use of herbicide, as well as not being compatible with the aims of the Wildland project, is not permissible within the terms of the organic status conferred by the Soil Association www.soilassociation.org/certification. Control of ragwort and other injurious weeds will therefore be undertaken by means of topping, which will be done at the end of July / beginning of August each year.  Topping earlier than this cannot take place because of ground-nesting birds.
  • Topping will be carried out every year as necessary, as ragwort and other injurious weeds may re-grow or re-colonise from the land outside the buffer zone on KCE as well as from plants outside the Estate. 
  • Prior to this Policy, the following measures have been taken to prevent the spread of ragwort:
    • Land where ragwort is present up to 100m inside the Estate boundary has been topped in August.
    • Two heavily ragwort-infested fields near Shipley have been topped.
    • Three fields adjacent to a neighbouring alpaca farm were topped.

The total elimination of all ragwort, creeping and common thistle, broad-leaved and curled dock from Knepp Castle Estate is not feasible and, as native wild plants with significant ecological importance, neither is it desirable or a legal requirement under the Injurious Weeds Act. 

Indemnity This report is based on information and research considered to be of good scientific origin, and is understood by the author and those consulted to be fair and accurate at the time of writing. It has been compiled on behalf of the Knepp Castle Estate, which is responsible for complying with UK legislation under the Weeds Act 1959. Any new information, provided that it comes from a reputable source, will be considered and any necessary adjustment will be made to the estate’s Control of Ragwort and other Injurious Weeds policy. This policy has been read by other organisations including Natural England and other members of the Knepp Wildland Project Steering group.  

The estate will endeavour at all times to follow the Defra Code of Practice on ragwort control, and to control the spread of other species  cited in the Injurious Weeds Act 1959. The Knepp Wildland Project is a legitimate use of land by its owner. As with all land usage and change, there are some that will be in favour and some that will not.


Cooper, M.R. & A.W.Johnson, A.W. (1988) Poisonous Plants and Fungi HMSO.  

Grime, J.P., Hodgson, J.G. and Hunt, R. (2007) Comparative Plant Ecology Castlepoint Press.  

Salisbury, Sir E. (1964) Weeds and Aliens. New Naturalist No. 43, Collins 






For more information, look at this extract from Buglife’s fascinating website  www.buglife.org.uk