No, it is a biennial, meaning it completes its life cycle in two years.

How do I get rid of it?

The best method is to cut the taproot below the soil surface before it sets seed.

Plant guide

Bull thistle.

Cirsium vulgare

Pronounced SUR-see-um vul-GARE-ee

Also known as Black Thistle, Boar Thistle, Bull Thistle, Common Thistle, Green Thistle

The bull thistle is a biennial plant that is often considered a weed in many parts of the world. It produces beautiful, purple flower heads that attract plenty of pollinators like bees and butterflies. You'll usually find it growing in disturbed soil, pastures, or along roadsides.

At a glance

Care level: Easy
Plant type: Biennial herb
Light: Full sun
Indoor light: Direct sun
Water: Every 7 to 14 days
Mature size: 5 feet
Growth rate: Fast
Hardiness: USDA 3 to 9
Bloom time: Mid summer to early autumn

Care

This plant thrives in full sun and well drained soil without any special attention. Watch for its aggressive spread, as it can quickly take over garden beds if you don't remove the flower heads before they go to seed. It is quite hardy and rarely needs supplemental care once established.

Watering: Water only during extended dry spells once the plant is established.
Feeding: Fertilizing is generally unnecessary as this plant grows vigorously in most soil conditions.
Pruning: Remove flower heads before they turn to seed to prevent unwanted spread.
Repotting: This plant is rarely grown in containers, but if you do, move it to a larger pot if it becomes root bound.
Soil: Well drained, fertile soil
Soil pH: 6.0 to 7.5
Temperature: -30 to 35°C
Humidity: 30 to 70%
Drought tolerance: Moderate
Lifespan: Biennial, typically 2 years.
Fragrance: Light
Deer and rabbits: High

Safety

People: The plant is not toxic, but the sharp spines can cause significant skin irritation and puncture wounds.
Children: Keep children away from this plant because the long, stiff spines can easily pierce soft skin.
Contact allergens: Handling the plant without thick gloves will result in painful skin punctures from the sharp spines.
Airborne allergens: The fine, windborne pappus attached to the seeds can cause respiratory irritation if inhaled in large quantities.
Edibility: While the young stems and roots are technically edible, the sharp spines make harvesting extremely difficult and risky.

How to identify it

Deeply lobed, prickly leaves
Large, purple, globe shaped flower heads
Stems covered in sharp spines
Rosette form during first year
Tall, branched flowering stalks

Height: 0.6 to 1.5m
Spread: 0.3 to 0.9m
Leaves: green, gray-green, deciduous
Flowers: purple, pink, 3 to 5cm
Fruit: brown, Autumn

Problems to watch for

AphidsCommon
RustCommon
CaterpillarsUncommon
Powdery MildewUncommon

By symptom

Plant problems by symptom

Check your bull thistle from a photo

Pocket Botanist looks at a photo of your plant and tells you what's wrong and what to try first.

Growing it

Propagation: seed
When to plant: spring, autumn
Overwintering: The first year rosette stays green through winter in mild climates. No special protection is needed.
In containers: Not recommended for containers due to its deep taproot and aggressive nature.

Seed

Collect seeds in late autumn when the heads turn brown.
Sow seeds directly into disturbed soil in early spring.
Keep the area clear of competing grasses until the rosette establishes.

Plant in areas where you want to support pollinators but can tolerate aggressive spreading.

Grows well with

Common Yarrow · They share similar soil and light requirements in open meadows.

Similar species

Canada Thistle · It is a perennial that spreads by rhizomes rather than just seeds.

Science

Family: Asteraceae
Genus: Cirsium
Order: Asterales
Class: Magnoliopsida
Native range: Europe, Western Asia, and North Africa.
Conservation: It is considered an invasive weed in many parts of North America and Australia, often subject to local control mandates.

It thrives in disturbed soils and open pastures where it can quickly colonize bare ground.

Value to wildlife: nectar source, seed source for birds
Pollinators: bees, butterflies, moths
Uses: pollinator garden, wildlife habitat

Through the year

JFMAMJJASOND

Flowering

Fruiting

Foliage

Ecological indicators

Salinity: 2/9
Soil reaction: 6/9
Light: 8/9
Temperature: 5/9
Moisture: 4/9
Nutrients: 6/9

Taxonomy resolved against GBIF.

Questions people ask

Is it a perennial?: No, it is a biennial, meaning it completes its life cycle in two years.
How do I get rid of it?: The best method is to cut the taproot below the soil surface before it sets seed.

Where the name comes from

Cirsium comes from the Greek word kirsion, a name used for a type of thistle, while vulgare means common.

Good to know

The seeds are a favorite food source for goldfinches.
It is the national flower of Scotland.
A single plant can produce thousands of seeds that travel long distances on the wind.

Keep your bull thistle growing

This page is a general guide. Save your plant in Pocket Botanist and you get care reminders timed for this plant, plus a care history that shows what worked.

Get the app

This guide was generated with AI on September 26, 2026 and checked against GBIF taxonomy. It is general information, not horticultural or veterinary advice. Read about how we build these guides.