Weed of the Week: Common Ragwort Senecio jacobaea L.

Laurence Gale MScJun 25, 2004in Consultancy

By Laurence Gale

What is a weed? By definition a weed is a plant that is growing in the wrong place. Weeds take valuable space, water, sunlight and nutrients that may otherwise be accessible to important crops, in our case turf grasses. Weeds not only compete for these resources they can disfigure and cause problems to playing surfaces.

Weeds are very good competitors and take advantage of any opportunities to colonise turf situations, particularly when the sward is under stress and weak, leaving bare soil areas for weeds to populate. Weeds have many mechanisms and characteristics that enable them to do this, having thick waxy cuticle leaves that can be resistant to some chemicals, fast reproduction methods, the ability to reseed in 6 week cycles and deep tap roots enabling the weed to survive in compacted dry ground conditions.

Weeds have one of three life cycles: annual; biennial or perennial.

Annual weeds: Live for a single season. These weeds germinate from seed in the spring or summer, flower and then die.
Biennial weeds: Live for two seasons. During the first growing season, these weeds remain in a vegetative stage and, in the following year, produce flowers, set seed and die.
Perennial weeds: Live for multiple seasons and flower more than once. Perennial structures (rhizomes, stolons, crowns, entire plants or roots) survive from year to year.

Some weeds may be harmful to the environment or noxious to your regional ecology. For example Japanese Knotweed (Fallopia Japonica) is fast becoming a major weed problem on road side verges and urban landscape areas, a very difficult weed to eradicate. It is very important to recognise weeds and seek effective controls methods to eradicate them from our facilities.

Weeds can also be used as an indicator of soil conditions. For example, knotweed and plantains both indicate soil compaction because they can maintain adequate root respiration at lower oxygen diffusion levels than other plants. Different weeds tolerate different soil conditions, some are alkaline loving and others acid loving. Getting to understand and recognise the physiology of these plants will help you become better turfgrass managers.

This week's weed is: Common Ragwort Senecio jacobaea L.

Common Ragwort is a native plant to the UK, and can now be seen colonising many fields and road side verges. The plant is quite distinctive with it's bright yellow flowers and feathery foliage. This plant supports a wide variety of invertebrates and is a major nectar source for many insects. However, Ragwort is one of five injurious weeds covered by the provisions of The Weeds Act 1959. Ragwort is poisonous to horses, ponies, donkeys and other livestock, and causes liver damage, which can have potentially fatal consequences. Under the Weeds Act 1959, the Secretary of State may serve an enforcement notice on the occupier of land on which injurious weeds are growing, requiring the occupier to take action to prevent the spread of injurious weeds. See link to DEFRA site.

In many situations ragwort poses no threat. It is a natural component of types of unimproved grassland. However, it is necessary to prevent its spread where this presents a high risk of poisoning horses, livestock or contaminating fields used for the production of forage.

The British Horse Society (BHS) sponsored Ragwort Control Act became law on 20 February 2004, some fourteen months after it was declared in the 2002 Private Members' Bill parliamentary ballot. See Link BHS.

Scientific name Family Life cycle	Senecio jacobaea L. Asteraceae biennial
Form / Appearance	Common Ragwort is an erect plant usually 30-100cm high, stems are tough and often tinged red near the base. The plant has bright yellow flowers that form on long stems. Common Ragwort is widespread throughout the UK and can be found on wasteland, development land, roadside verges, railway land, amenity land, conservation areas, set-aside, woodland and grazing land.
Roots	Root are fibrous
Flowers	Flower heads are flat and very conspicuous, with densely packed yellow flowers with ray florets and disc florets, all of which are bright yellow.
Leaves	Leaves are dark green and deeply dissected, with irregular, jagged-edged lobes.
Reproductive method	It spreads primarily by seed, a single ragwort plant may produce up to 150,000 seeds, which may remain viable for up to 15 years.
Habitat	Common Ragwort can be found over a large range of soil types and climatic conditions and can be characteristic of badly managed grasslands, verges and public open space.
Miscellaneous info	Common Ragwort is normally a biennial. During its first year of growth it establishes a rosette of basal leaves and in the second year produces numerous flower heads. Flowering usually occurs from June until late October after which the plant dies. Common ragwort can also behave as a perennial (flowering every year)
Cultural Control	Once this weed gets established, it is often difficult to remove or eradicate. However, there are a number of ways now being used to eradicate or reduce the spread of this weed. In most cases they are labour intensive: Pulling the weed is a common cultural practice of controlling ragwort, removing the weed from site. Care should taken to ensure the whole root is removed to prevent the weed re-establishing. Often a time consuming process. Digging out the plant. Often this process must be repeated a number of times to remove all signs of roots. Cutting on a regular basis. Continue to cut down the vegetation back to ground level and keep cutting it to prevent the weed from flowering, thus controlling its spread from seed. A combination of cutting and herbicide is probably the most effective. Chemical control is expensive, not always 100% effective and can have a negative effect on the environment. It is important to remove or burn all collected vegetation. Always wear gloves when handling ragwort.
Chemical Control	Apply non-selective herbicides when plant growth is active. There are a number of products available for controlling Ragwort. These chemicals are best used when the weeds are actively growing, usually between April-October. Particular care should be taken when using chemicals near to water courses, rivers, streams and ponds. Roundup pro biactive. (Contains 360g/L glyphosate. Scotts. Roundup Pro Green. (contains 450g/l glyphosate present as 590g/l (50.9% w/w) of the isopropylamine salt of glyphosate. Rigby Taylor. Timbrel (Contains 667g/L(44.3%w/w) triclopyr butoxy ethyl ester. (480 g/L triclopyr acid equivalent). Bayer Environmental Science. These herbicides are usually applied as a liquid using watering cans, knapsack sprayers and vehicle mounted sprayers. Ensure you follow manufacturer's directions, health & safety and product data sheets, and comply with COSHH regulations, when using these chemicals. Herbicides are an effective tool where high quality turf is desired. However, they must be applied with care and accuracy and in the context of a good overall turf management program. Before using any herbicide, carefully review the label for conditions of use including rates, methods of application, and precautions. Never use a herbicide in any manner contrary to its label and be sure that the herbicide will not injure the turfgrass species