Marsh ragwort

How to recognise it

Habit

Upright plant of 30–80 cm that branches widely from the middle, biennial or short-lived perennial.

Leaf

Lower leaves oblong, undivided or with a large, oval end lobe and a few small side lobes; upper leaves pinnately lobed. Glossy green, often tinged purple.

Flower

Yellow heads of 2.5–3 cm with 12–15 ray florets, in a loose, widely spreading cluster, from July to September.

Fruit/Seed

Small seeds with a white pappus, carried by the wind.

Stem

Sturdy, often tinged purple and almost hairless.

Confused with

Common ragwort grows on drier ground, has more deeply cut leaves and a denser, flatter flower cluster. Narrow-leaved ragwort has narrow, linear leaves and is on the Belgian list of invasive species.

Flowering: July–September · Pruning: August–September

Why grow it?

• A rich source of nectar and pollen in summer for bees, hoverflies, butterflies and beetles.
• Food plant of the cinnabar moth: its yellow-and-black striped caterpillars feed on ragworts.
• Characteristic of flower-rich wet hay meadows, together with ragged-robin, greater bird’s-foot trefoil and marsh thistle.
• A striking yellow flower for a wet wildflower meadow or a pond edge.
• Flowers in summer, after the spring flowers of wet grassland, and so extends the flowering season.

Marsh ragwort: where does it grow best?

• In the wild: wet hay meadows and pastures, ditch sides, stream banks, damp dune slacks and marsh edges.
• Sun to light partial shade.
• Wet to moist, moderately fertile soil: clay, loam, peat or sand; it tolerates winter flooding.
• In the garden: in a wet wildflower meadow or by a pond, well away from horses and other livestock.

Goes well with

• Ragged-robin: Pink flowers in May–June in the same wet hay meadow.
• Greater bird’s-foot trefoil: Yellow pea flowers on wet ground, for bumblebees.
• Purple loosestrife: Purple spikes along the same ditch, in July–August.
• Meadowsweet: Creamy plumes in summer beside the yellow heads.
• Marsh thistle: Purple thistle flowers for butterflies in a wet meadow.

Marsh ragwort: when and how to plant it?

1. Buy seed or plants of native origin from a nursery for wild plants.
2. Sow in September–October on a damp, open spot; the seed germinates readily in spring.
3. Press the seed in, barely cover it and keep the soil moist.
4. Set plants 30–40 cm apart, in March–April or September–October.
5. Do not sow or plant it in or next to a field grazed by horses, cattle or sheep, or in grassland you cut for hay.
6. Never dig up plants from the wild.

Care

Water

Only needed if the soil dries out in summer; a wet spot is better.

Feeding

Not needed; fertiliser makes the grass too strong and crowds out the flowers.

Mowing

Mow the meadow in September, after flowering, and remove the cuttings. Never use the cuttings as hay or silage.

Letting it seed

Let some of it set seed if you want to keep it: as a biennial it needs new seedlings and small bare patches every year.

Spreading

On wet, open ground it self-sows readily. Pull plants out, wearing gloves, where you do not want them.

Tip: Only grow marsh ragwort in a wet wildflower meadow that you do not cut for hay and where no livestock graze: then you can enjoy the flowers and the cinnabar moth without worry.

Pruning and mowing

Pruning months: August–September.

When: In August–September, after flowering.

How:

• Mow or cut the spent stems and take them away, never for fodder or bedding.
• If you want seed, let a few plants ripen before mowing.
• Leave a strip standing for insects, but not next to a field with livestock.
• Wear gloves for the job.

Caution: Never use cuttings containing marsh ragwort as hay, silage or bedding for animals.

Pruning: when and how · Pruning calendar and basic rules

Propagation

Seed

Ripens from August. Sow it in autumn on open, damp ground; it also self-sows.

Marsh ragwort: how does it get through the winter?

Hardy to −25 °C.

• Young plants overwinter as a leaf rosette and flower the following year.
• Flowering plants usually die after setting seed.
• Hardy to about −25 °C and tolerant of flooding.
• Cinnabar moth caterpillars pupate in the soil or leaf litter and overwinter as pupae.

Diseases and pests

• Poisonous to livestock: Contains pyrrolizidine alkaloids. Keep it out of pastures and hay meadows, and pull it out, wearing gloves, where animals graze.
• Self-sowing: On wet, open ground it can spread quickly. Mow before seed set where you do not want it.
• Stripped plants: Cinnabar moth caterpillars can strip a plant bare. Leave them: the plant recovers or self-sows, and the moth is a lovely guest.
• Drying out: On soil that is too dry it disappears. Choose a wet spot.

Through the year

• March: The rosettes start growing again; set out plants.
• April: The rosettes get bigger.
• June: Flowering stems shoot up; cinnabar moth caterpillars may appear.
• July: First yellow flowers.
• August: Full flower; mow from late August.
• September: Last flowers; mow and remove the cuttings. Sow.
• October: Sow on open, damp ground.
• December: Rest; the rosettes overwinter.

Did you know?

• Marsh ragwort was long known as Senecio aquaticus; DNA research placed it, together with common ragwort, in the genus Jacobaea.
• The name Jacobaea refers to Saint James: around his feast day, 25 July, the ragworts are in flower.
• Cinnabar moth caterpillars store the plant’s poison in their bodies, which makes them inedible to many birds; their yellow and black stripes are a warning.