Purple Star-Thistle
ExplorePlants
Purple Star-Thistle
centaurea calcitrapa
The Purple Star-Thistle (Centaurea calcitrapa) is a hardy, branching biennial herb famous for its formidable defense mechanisms. Native to the Mediterranean basin, this member of the sunflower family (Asteraceae) has successfully spread to many temperate regions globally, often becoming an aggressive invasive weed. It plays a dual role in ecosystems: while it is notorious for invading agricultural lands, degrading pastures, and crowding out native flora, its flowers provide a vital source of nectar for bees and other pollinators during the late summer months. Its resilient nature allows it to thrive in nutrient-poor, dry, and heavily disturbed soils where other plants struggle. Its scientific name 'calcitrapa' perfectly captures its spiked physical nature, evoking the imagery of medieval spiked caltrops designed to deter cavalry. Want to find and snap Purple Star-Thistle yourself? Get the Snappit app.
Habitat: Typically found in dry, disturbed areas such as overgrazed pastures, agricultural fields, waste lands, and sandy roadsides.
Appearance
This plant is easily identified by its highly branched, bushy growth form that can reach up to one meter in height. Its most distinctive features are the flower heads: small, pale purple to pinkish florets sitting atop a base heavily armored with stout, sharp, straw-colored spines measuring up to 2.5 centimeters in length. The lower leaves are deeply lobed and form a rosette close to the ground, while the upper leaves are smaller, narrow, and lack lobes, clinging tightly to the tough, ridged, and finely haired stems.
KingdomPlantaePhylumTracheophytaClassMagnoliopsidaOrderAsteralesFamilyAsteraceaeGenusCentaurea
Category
PlantsRarity
Common
Danger
1/5 · Very low
Snaps
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Interesting facts
Its spines are so formidable that they can injure grazing livestock, often forcing animals to avoid pastures entirely when infestations are heavy.
Purple Star-Thistle seeds have been known to contaminate commercial seed mixes and hay, helping it easily spread across continents.
The species name 'calcitrapa' comes from the Latin word for 'caltrop', a multi-pointed iron weapon used in medieval warfare to obstruct horses, referring to the plant's painfully sharp spines.
Special abilities
Ability
Spiny Caltrop Armor
The flower heads are surrounded by incredibly sharp, rigid spines that deter grazing herbivores and protect the developing seeds.
Ability
Deep Taproot System
A robust, deep taproot allows the plant to access moisture and nutrients deep in the soil, ensuring survival during hot, dry summer droughts.
Ability
Prolific Seed Production
A single plant can produce thousands of seeds that can remain dormant and viable in the soil for several years, waiting for ideal growth conditions.
Measurements & details
- Length
- 20-100 cm
- Lifespan
- 1-2 years
Diet & Feeding
As a photoautotrophic plant, it manufactures its own energy from sunlight, water, and carbon dioxide through photosynthesis.
Primary Foods
- Sunlight
- Water
- Carbon dioxide
- Soil nutrients
Ecological connections
eaten by
Knapweed peacock fly
Chaetorellia acrolophi
The larvae of this fly feed on the seeds inside the flower heads, making it a biological control agent.
mutualism
Western Honey Bee
Apis mellifera
Bees pollinate the purple flowers while foraging for abundant nectar and pollen.
competitor
Yellow Star-Thistle
Centaurea solstitialis
Competes aggressively with the purple star-thistle for space, water, and soil nutrients in dry pastures.
Traits
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Also known as
No aliases listed yet.
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Safety
Danger
1/5 · Very low
No special safety notes yet.
Frequently Asked Questions
How to identify Purple Star-Thistle?
The easiest way to identify Purple Star-Thistle is to use the Snappit nature identifier app.
How long is Purple Star-Thistle?
20-100 cm
How long does Purple Star-Thistle live?
1-2 years
What does Purple Star-Thistle eat?
As a photoautotrophic plant, it manufactures its own energy from sunlight, water, and carbon dioxide through photosynthesis.
Where is Purple Star-Thistle usually found?
Typically found in dry, disturbed areas such as overgrazed pastures, agricultural fields, waste lands, and sandy roadsides.
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