Ragwort

Ragwort is an invasive weed that spreads rapidly by the seeds in the wind. Although Ragwort is not a particular issue in gardens, it is in pasture land as it is poisonous to horses and cattle which also can make it difficult for haymakers making sure their field are ragwort free.

This blog post will provide an in-depth guide on what Ragwort are, how they grow, and how to eradicate them from your garden.

Quick Facts

Common names: St. James’ wort, Tansy ragwort, Ragweed, Stinking Nanny/Ninny/Willy, Staggerwort, Dog Standard, Benweed, common ragwort, cankerweed
Scientific name: Senercio jacobaea
Family: Asteraceae
Origin: non-native
Flowering season: June to November
Habitat: roadsides, uncultivated ground, paddocks, pastures, waste ground, farmland, wetlands, sand dunes, alongside railway lines and woodland

Ragwort Identification

The daisy-like, yellow flower heads of common ragwort may appear attractive to the untrained eye, but they conceal the plant’s toxic nature. It is well-known as a weed of paddocks and pastures, where it can be damaging to cattle, but it is rarely a problem in gardens or waste ground.

It is, in reality, the foodplant of the black-and-red cinnabar moth, whose black-and-yellow-barred larvae can completely strip the leaves from the plant. Common ragwort is a biennial that blooms from June to November in its second year.

Ragwort is a tall plant, growing up to 3ft. It has large flat-topped clusters of yellow, daisy like flowers from July-October time. For the rest of the time, Ragwort is at its Rosette stage where the plant is a dark green colour with curly-edged leaves.

What do Ragwort look like?

Common ragwort is a relatively tall-growing plant that has clusters of yellow, flattened flower heads, and leaves that look ‘feathery’ because they are very divided.

Characteristics that make up the Ragwort leaf, stem, root and flower are detailed below.

Ragwort leaves are hard to spot without their distinctive flowers
Ragwort leaves are hard to spot without their distinctive flowers

Leaves: Wavy, lobed leaves (5-20 x 4-6 cm) emerge initially from a basal rosette.

Ragwort is a biennial that produces a rosette of leaves in the first year and flower stalks in the second year.

Its leaves are dark green on top, whitish-green underneath, and have deeply cut, blunt-toothed lobes with a ragged/ruffled appearance.

Ragwort towers easily to 3 feet with its long stems
Ragwort towers easily to 3 feet with its long stems

Stem/Spikes: Can grow up to 4 feet tall with erect stems which branch near the top with clusters of bright-yellow, daisy-like flower heads.

Roots: Well-established ragwort plants spread rootstock that can be branched and frequently produces a group of offsets. The original taproot rarely survives, and new development is provided by a secondary system of coarse white roots that sprout from the rootstock and lower stem nodes.

These roots or fragments of 1cm quickly invade surrounding areas. This process is accelerated by damage to the parent plant. Roots on a first-year crown can regenerate starting in September of the first year, but as September approaches the ability to regenerate is gradually lost, and these roots eventually die.

With the fresh crowns, the cycle is repeated. Roots that have been severed but not disturbed are more likely to regrow than those that have been disturbed.

The flower of the Ragwort weed exposing its seeds
The flower of the Ragwort weed exposing its seeds

Flowers: Ragwort produces a large number of yellow blooms in its second year of growth and continues to flower from June to November, after which the plant dies.

The flowering period is long, starting in mid-June and continuing until November, being especially prolonged if plants have been damaged in the first flush of flowering.

Seeds: Ripening in July/August the seeds are spread by wind. Maturing within 20 days a single plant can produce 150,000 seeds.

Two types of seed are produced in the flower head, each with different germination characteristics. Seeds from the disc florets at the centre of the flower head are lighter and have a pappus of hairs to aid long distance dispersal to new sites. The disc florets around the edge of the flower head produce heavier seeds with thicker coats and no pappus.

The Problem

Toxic alkaloids can be found in all parts of the plant, and liver injury is a common cause of cattle death. The Weeds Act of 1959 and the Ragwort Control Act of 2003 both mention it.

When there is enough grass, cattle and horses avoid ragwort, but newly set out stock may eat it if they are hungry. Sheep prefer it while they’re young and appear to be more resistant to it than cattle, but they’re not immune.

Ragwort poisoning is caused by the presence of ragwort in hay, silage, or dry grass. The toxic characteristics are unaffected by drying or similar treatments. The toxin can also reduce productivity of agriculture land.

Where some annual and biennial weeds can be eradicated by hoeing or cutting the tops off, ragwort will only thrive and keep forming new side shoot rosettes. This will in turn produce even more vigorous growth the following year.

Plants that have been cut pose a serious threat to grazing animals and can still set seed. If the plants have been pulled out, it will only solve the problem temporarily as the remaining can root will produce new shoots. The best method of control is chemical control.

Ragwort is uncommon in gardens, but it can be found in pony paddocks, railway embankments, and unimproved grassland areas. Poisoning is especially dangerous to cattle and horses. Cutting, wilting, and herbicide treatment make ragwort less unappealing to livestock, and poisoning is primarily caused by consuming contaminated hay.

Ragwort flowers cluster and become invasive within an area
Ragwort flowers cluster and become invasive within an area

How does Ragwort spread

Ragwort populations can experience substantial swings, with plant numbers abruptly increasing or decreasing for no apparent reason. A population of uniform age may flower, mature, and die at the same time. It’s been hypothesised that ragwort declines are linked to extremely dry summers.

Seeds buried more than 4 cm deep in the soil might be dormant for up to 16 years. Seeds in the upper layer of soil, on the other hand, die in 4-6 years, whereas seeds in cultivated soil last less than 4 years.

Ragwort has a deep root system and can regrow from its roots if they are not entirely destroyed, however it is largely spread by seed in clean pastures. The wind can carry seeds from disc florets up to 72.5 metres. The seed heads, on the other hand, remain closed and the seeds are not shed in moist conditions.

Water can also help disseminate ragwort seeds. The seeds float at first, then sink, then float again as they germinate. Seeds of common ragwort have been found in hay and as a contaminant in crop seeds.

The seeds are eaten by birds, although viable seeds are rarely seen in their droppings. Sheep ingest seeds, which pass through their digestive system unharmed.

Yellow flowering Ragwort during summer
Yellow flowering Ragwort during summer

Ragwort Seasonal Changes

The plant is usually a biennial (living only two years and flowering in its second year) but damage to the base of the plant can make the plant behave like a perennial (living indefinitely), as new rosettes are formed.

Rosettes are the circular arrangement of flower petals; or a cluster of leaves radiating from approximately the same point usually around a stem. Examples include aeonium and most succulent plants, African violets, primula, sempervivums.

Ragwort in Spring

In spring, the leaves of this plant have a spoon-like shape with jagged edges and its yellow flowers look like daisies. It’s yellow, easy to grow and spreads quickly. Ragwort (Jacobaea vulgaris) flowers in two stages, the first between February and April and the second from May to August.

Ragwort in Summer

Ragwort during summer is not very attractive. It looks like an overgrown weed and can be difficult to get rid of. The flowers in summer attract pollinating insects such as bumblebees and butterflies. In the summer months it is not unusual to find ragwort up to three metres in height.

Ragwort in Autumn

Ragwort’s most identifying characteristic in autumn is the distinctive bright yellow flowers. Leaves on mature plants are green and pointed, while leaves on young plants are more rounded.

Ragwort in Winter

In winter ragwort is much less visible as much of the plant is underground and the top of the plant may be disguised by frost and snow.

The rosette effect as the plant grows with long stems
The rosette effect as the plant grows with long stems

How to get rid of Ragwort

First, consider whether this can be done using non-chemical means such as digging out and where this is not feasible, chemical controls may need to be used.

Method One – Herbicide Treatment

Glyphosate (e.g. Roundup Ultra, SBM Job done Tough Weedkiller (soluble sachet only), Doff  Advanced Concentrated Weedkiller or Westland Resolva Pro Xtra Tough Concentrate; or for spot treatment use Roundup Gel) can be used to clear small infestations but apply carefully as it will kill any green plants it comes into contact with.

In rough grass use a selective weedkiller which contains triclopyr (SBK Brushwood Killer) as this would leave the grass unharmed. However, other broad-leaved plants will be damaged (e.g. wildflowers) and so should only be used in grass where such action is acceptable. For garden use only, consider using triclpyr (Vitax SBK Brushwood Killer) in rough grassed areas and lawn weedkillers for lawns.

Apply weedkillers in late April or May to suppress mature weeds in pastures. Because treated plants remain hazardous for at least four to six weeks after spraying, grazing is not safe for at least four to six weeks following spraying. Give the weeds plenty of time to decompose.

Established plants have remained in their current position for two or three years, and their root systems are well-developed, allowing for vigorous growth and healthy foliage and flowers.

Spraying is less effective on established plants, especially after the stem lengthens in early June. Summer seedlings can be controlled by spraying from September to November when the weather is pleasant and stable.

Ragwort seeds can survive in the soil for up to 15 years, so spraying should be done every autumn or every second spring. Weedkillers temporarily boost the attractiveness of ragwort to grazing stock, thus keep animals off sprayed fields until the herb has dissolved and vanished to ensure that poisoning does not occur.

Only qualified specialists have access to weedkillers suitable for large-scale pasture use. To treat paddocks and other similar areas, contact agricultural contractors (see the National Association of Agricultural Contractors). Consider applying triclpyr (Vitax SBK Brushwood Killer) in rough grassed areas and lawn weedkillers in lawns for garden use only.

Method Two – Digging or pulling it out

When trying to eradicate ragwort all the root must be removed or the plant will grow back again.

Non-chemical options are limited. Cutting at the early flower stage reduces seed production but can stimulate the growth of side shoots, resulting in more

Cutting at the early flower stage reduces seed production but can stimulate the growth of side shoots, resulting in more vigorous growth in the following year

Cut plants are a serious risk to grazing animals and may still set seed. They should be removed and burnt.

Mowing is at best a short-term measure to prevent seed production, in reality it causes plants to perennate and persist.

Pulling is practical where weed numbers are low, but the benefit is only temporary. Roots remaining in the soil will give rise to new plants.

Bold Management of Ragwort

Chemical spraying needs to be done routinely as ragwort seeds can remain dormant in the soil for up to 15 years. It is also very important that although each chemical has its own exclusion period to keep grazing animals off, they cannot be returned until the dead plants have been removed as they will still cause harm to the livestock.

The Ragwort Control Act 2003 in the United Kingdom has resulted in the publication of a code of practise by DEFRA that provides guidelines on limiting the spread of ragwort in situations where it poses a risk to horses and other livestock. The code does not strive to eradicate ragwort; rather, it seeks to control it when it poses a harm to animal health and welfare.

The Code of Practice’s advice on disposal choices for common ragwort has been supplemented with guidance on disposal alternatives for common ragwort, which should be read in combination with it.

Ragwort will not establish in grassland if a dense, robust sward is maintained on well-drained land. Controlled grazing to keep the sward at the right height can also help. Sheep grazing in the winter and spring weakens ragwort plants, however there is some risk to the animals in strongly contaminated pastures.

In Conclusion

Ragwort is a tough plant but with this guide outlining all areas for attack, we hope you’re ready to fight back against this enemy before they get too far into your garden again!

Ragwort is a very adaptable weed that grows in our gardens today and is one of the most resistant. However, using one of the products mentioned below will eliminate it.