Scientific Name: Centaurea melitensis
Common Names: Maltese Star-thistle, Tocolote, Tocalote, Spotted Knapweed, Malta Starthistle
Duration: Annual, Biennial
Growth Habit: Herb/Forb
Arizona Native Status: Introduced
Habitat: Desert. This weed grows in disturbed areas, along roadsides, in fields, and in drainage ditches.
Flower Color: Yellow
Flowering Season: Spring
Height: To 3 feet (91 cm) tall
Description: The 1/2 inch (1.3 cm) wide flower heads are surrounded by spiny, cobwebbed bracts. The floral spines are tan-colored, 1/2 inch (1 cm) long, and have a reddish, pinnately spined base. These spines are painfully sharp and can cause injury to grazing animals if the plants are eaten. The upper leaves are linear, while the lower leaves are pinnately lobed.
The similar Yellow Star-thistle (Centaurea solstitialis) has longer, yellow spines.
Poisonous – This plant can be poisonous to horses.
Kingdom: Plantae – Plants
Subkingdom: Tracheobionta – Vascular plants
Superdivision: Spermatophyta – Seed plants
Division: Magnoliophyta – Flowering plants
Class: Magnoliopsida – Dicotyledons
Family: Asteraceae – Aster family
Genus: Centaurea L. – knapweed
Species: Centaurea melitensis L. – Maltese star-thistle
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