Classification Hierarchy
Kingdom Plantae
Subkingdom Tracheophyta
Superdivision Spermatophyta
Division Magnoliophyta
Class Magnoliopsida
Subclass Asteridae
Order Asterales
Family Asteraceae
Genus Cirsium
Species Cirsium hillii
Hill's thistle

Date: XXXXXXXX 2010. Location: XXXXXXXXX(map)


Scientific Name: Cirsium hillii [syn. C. pumilum]

Common Name: Hill's thistle

Origin: Native (biennial or monocarpic perennials)

Notes: This non-aggressive native thistle has a tenuous existence in Iowa and is legally rated as an "Endangered species". Ironically, all members of its genus (Cirsium) are designated as Primary Noxious Weeds. Consequently, the plants existence is both encouraged and condemned at the same time. The species is worth preserving and it shouldn't be harmed. It is relatively easy to distinguish from other thistles by its short stature (less than 2 feet tall), usually having a single thick stem supporting a single floral head. If there is a branch on the stem it will also have a single floral head. The impression is of a short, stocky thistle with a single large floral head. The FNA describes this plant as Cirsium pumilum which has two varieties —var. hillii with phyllaries having spines less than 3 mm and var. pumilum having phyllaries spines longer than 3 mm .

Additional references: 1, 2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, 13.

Field Marks for Identification:

Flowers: June; purplish-pink; floral head is 2 to 3 inches tall, supported on a peduncle elevated above the highest leaves.

Leaves: 5-30 cm long, undulate, pinnatifid, lobes become spinose and are usually separated by wide sinuses; cauline leaf bases often clasping; margins covered with fine spines.

Stems: erect, thick, villous with septate trichomes, often unbranched, supporting a single floral head.

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

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