Classification Hierarchy
Kingdom Plantae
Subkingdom Tracheophyta
Superdivision Spermatophyta
Division Magnoliophyta
Subclass Asteridae
Order Asterales
Family Asteraceae
Genus Cirsium
Species Cirsium discolor
Field thistle

Date: XXXXXXXX 2010. Location: XXXXXXXXX(map)

BONAP, FNA, ITIS, USDA, VPI

Scientific Name: Cirsium discolor

Common Name: Field thistle

Origin: Native

Notes: Designated a "Primary Noxious Weed" by Iowa weed law.
A biennial (sometimes perennial) plant with a strong taproot system.

Additional references: 1, 2, 3, 4, 5, 6, 7, 8, 9, 10.

Field Marks for Identification:

Flowers: purplish-pink to white; heads 1-many; involucres 2.5-3 cm high, thinly arachnoid; phyllaries spines abruptly spreading to deflexed, spines slender 3 to 9 mm long; cypselae tan to brownish, 4-5 mm long, pappi 18 to 25 mm.

Stems: erect with few to many branches ascending; strongly furrowed, greenish, villous with septate trichomes, sometimes smooth or tomentose; 2 to 6 feet high.

Leaves: prickly and numerous, cauline and basel leaves deeply pinnatifid; above—green and glabrous or with short stiff hairs, below—blanketed with dense white hair; uppermost sessile leaves form a false involucre.

Glossaries of botanical terms: 1, 2, 3, 4, 5, 6, 7, 8, 9, 10.

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