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Noxious Weeds

A noxious weed is a plant species which has been designated by a statutory authority as one that is injurious to agriculture, horticulture, habitats/ ecosystems, humans or livestock. They are usually injurious to human or animal health (through contact or injection), the latter of which causes economic loss to humans. Noxious weeds can be native or introduced. A native species may not pose a threat when growing in a natural forest type situation, but becomes a problem with changing landscape; e.g. clearance to cultivation. They are usually plants, which multiply aggressively and without any natural control such as herbivores or soil or climatic conditions.


Example of Noxious Weed

Ragwort (Senecio Jacobea) is also known as ragweed, buachalán and buachalán buidhe (in Ireland). Ragwort is highly toxic to cattle, horses, deer, goats, pigs and chickens. The poisonous substances in ragwort are toxic alkaloids (Jacobine, Jacodine and Jaconine). These cause the liver to accumulate copper, causing ill heath and death. The poisonous material contained in ragwort is not destroyed by drying. Hay containing ragwort is particularly dangerous. Grass silage containing ragwort is also a serious source of poisoning. Seed is the principle method of spreading this weed, but root fragments are also capable of reproduction. Each plant produces 50,000-200,000 seeds over a 4-6 week period (July-Sept). Ragwort is a biennial plant, i.e. it grows from seed and remains in the rosette stage for the first growing season. In the following year it produces its familiar golden yellow flowers on a stem varying in height from 45 to 75 cm.

Ragwort Flowerhead
Ragwort Flowerhead


Ragwort Young Plant
Ragwort Young Plant
Ragwort Seed Head
Ragwort Seed Head

The Law

The Law in Ireland

NOXIOUS WEEDS ACT, 1936; Number 38 of 1936

SI_1937_103 — Noxious Weeds (Thistle, Ragwort, and Dock) Order, 1937

SI_1965_189 — Noxious Weeds (Male Wild Hop Plant) Order, 1965.

SI_1973_194 — Noxious Weeds (Wild Oat) Order 1973.

Liability of responsible persons in respect of noxious weeds

3.—Where any noxious weeds are growing on any land the responsible person in respect of such land or if there are two or more such persons, each of them severally, shall be guilty of an offence under this section and shall be liable on summary conviction thereof to a fine not exceeding twenty pounds.


The Law in England and Wales

The Weeds Act 1959 specified a number of weeds, which it described as ‘injurious weeds’

Spear Thistle (Circium vulgare)

Creeping or field Thistle (Circium arvensis)

Curled leaved Dock (Rumex crispus)

Broadleaved Dock (Rumex obtusifolius)

Common Ragwort (Senecio jacobaea)

Ragwort Control Act 2003 resulted with the threatened repeal of the Weeds Act that provoked a public debate, which eventually led to the Ragwort Control Act 2003.

Wildlife & Countryside Act 1981 has a much broader remit and includes what may otherwise be termed ‘invasive species’. Species included are Japanese Knotweed (Fallopia japonica) – and Giant Hogweed (Heracleum mantegazzianum)

Environmental Protection Act 1990 which largely relates to the issue of waste. It specifie Japanese Knotweed and Giant Hogweed and places a 'Duty of Care' on the producer (and anyone they employ) to dispose of soil or other material contaminated with Japanese Knotweed or Giant Hogweed. It became a controlled waste, which can only be taken to licensed landfill sites.


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