Conservators have pledged to take action over the spread of a poisonous weed on Therfield Heath.

Ragwort is a tall weed bearing yellow daisy-like flowers that sprouts from July to October mainly in pony paddocks, railway embankments and uncultivated areas.

Angela Louch, who lives in Royston, raised her concerns about the spread of the wild flower on last week’s Royston Crow letters page, citing Therfield Heath as a problem area.

Responding, clerk to the Conservators of Therfield Heath David Smith said: “Last week’s Royston Crow letter page highlighted the dangers of ragwort growing in the countryside, particularly on Therfield Heath. The Conservators have a programme to remove the ragwort from Therfield Heath. This is then taken away and destroyed.

“They are concerned about all the areas of high botanical interest and in particular the area known as the Rifle Range which stretches south, south-east from the Heath Sports Club.

“By the time this is published the majority of the ragwort will have been removed by hand from the heath, a costly but very necessary exercise.”

Mrs Louch is also worried about the appearance of Ragwort along the A505 between Baldock and Royston. She said: “The trouble is once the flower goes to seed and blows everywhere it gets into the tyres of passing cars or gets dragged along behind the vehicles and it is now growing all along the dual carriageway to Baldock.”

Cattle and horses can be particularly susceptible to poisoning and the British Horse Society has sent a petition with 951 signatures requesting “that Herts County Council take its responsibility seriously and actively engages in reducing ragwort growth”.

A county council spokesman said: “HCC fulfils its responsibility to effectively control Ragwort on property directly under council control. However, in most cases the land is let out and responsibility for the control of the plant then lies with the tenant farmer.

“On all sites where the county council’s Countryside Management Service is involved there is a defined and signed off management plan. In sites where grazing takes place and Ragwort is present, control of this species is included.

“It should also be noted that the Ragwort control is mechanical, not chemical. This usually comprises large groups of volunteers lifting ragwort out relatively early in the season to prevent further spread through seed dispersal.”

Therfield Heath and Greens are managed by Conservators, who are elected locally for three-year periods. The land is owned by the Therfield Regulation which is a registered charity.

The heath is designated as a local nature reserve and a Site of Special Scientific Interest as it is one of the largest areas of unimproved chalk grass land in the country.