Marsh thistle.

At a glance

Care level

Easy

Plant type

Biennial herb

Light

Full sun to partial shade

Indoor light

Direct sun

Water

Every 1 to 3 days

Mature size

1.5 meters

Growth rate

Fast

Hardiness

USDA 4 to 8

Bloom time

Mid to late summer

Care

Keep the soil consistently moist as this plant naturally grows in wet meadows. Watch for aphids on the flower buds during the summer months. Ensure it has plenty of space to reach its full height.

Watering

Keep the soil damp at all times to mimic its natural wetland environment.

Feeding

This plant typically does not require supplemental fertilizer when grown in rich, moist soil.

Pruning

Remove dead flower stalks after the plant has finished blooming and set seed.

Repotting

This species is best grown in the ground and is not typically suited for container culture.

Soil

Moist, boggy, or damp soil

Soil pH

Neutral to slightly acidic

Temperature

-34 to 30°C

Humidity

40 to 80%

Safety

People

The plant is not toxic but the sharp spines can cause painful skin punctures.

Pets

This plant is generally considered non-toxic to cats and dogs, though the spines can cause physical irritation.

Children

Keep children away from the sharp, spiny stems to prevent accidental scratches or punctures.

Contact allergens

The sharp spines and stiff hairs can cause mechanical skin irritation.

Airborne allergens

The fine, windborne seeds can be a minor respiratory irritant to sensitive individuals.

Edibility

This plant is not considered edible and may cause digestive distress if consumed.

How to identify it

• Tall, spiny, winged stems
• Deeply lobed, prickly leaves
• Clusters of small purple flower heads
• Biennial growth habit

Height

0.5 to 1.5m

Spread

0.3 to 0.6m

Leaves

green, deciduous

Flowers

purple, pink, 1 to 2cm

Fruit

brown, white, Autumn

Problems to watch for

• AphidsCommon
• RustCommon
• Slugs and SnailsCommon
• CaterpillarsUncommon
• Powdery MildewUncommon
• Root RotUncommon

Growing it

Propagation

seed

When to plant

spring, autumn

Plant in groups to create a dense nectar source that draws in pollinators from across the garden.

Grows well with

• Purple Loosestrife · They share similar moisture requirements in wetland settings.
• Meadowsweet · This companion thrives in the same damp, meadow conditions.

Similar species

• Spear Thistle · A larger, more aggressive thistle that prefers drier ground.
• Creeping Thistle · A persistent perennial that spreads via underground runners.

Science

Family

Asteraceae

Genus

Cirsium

Order

Asterales

Class

Magnoliopsida

Native range

Europe and parts of western Asia.

Conservation

This species is common and not of conservation concern.

It acts as a pioneer species in damp meadows and woodland clearings, providing essential nectar for late-season insects.

Value to wildlife

nectar source, larval host plant

Pollinators

bees, butterflies, moths

Uses

pollinator garden, wildlife meadow, wetland restoration

Taxonomy resolved against GBIF.

Questions people ask

Is this plant invasive?

It can spread readily by seed in suitable damp habitats but is generally considered a native wildflower.

Does it need a lot of water?

Yes, it prefers consistently moist to wet soil and does not tolerate drying out.

Where the name comes from

The name Cirsium comes from the Greek word for a thistle, while palustre refers to its preference for marshy, swampy habitats.

Good to know

• It is a biennial plant, meaning it completes its life cycle in two years.
• The flowers are highly attractive to various species of bumblebees.
• It thrives in damp, boggy ground where other plants might struggle.
• The seeds are equipped with feathery plumes to help them travel on the wind.