Cirsium hydrophilum

Cirsium hydrophilum
Cirsium hydrophilum
Suisun thistle
Conservation status

Critically Imperiled (NatureServe)
Scientific classification
Kingdom: Plantae
(unranked): Angiosperms
(unranked): Eudicots
(unranked): Asterids
Order: Asterales
Family: Asteraceae
Tribe: Cynareae
Genus: Cirsium
Species: C. hydrophilum
Binomial name
Cirsium hydrophilum
(Greene) Jeps.

Cirsium hydrophilum is a species of thistle which is endemic to California, where it is found only in the San Francisco Bay Area and the Sacramento-San Joaquin River Delta. This native thistle grows in wet boggy habitats.

Contents

Description

The Cirsium hydrophilum thistle may reach 2 metres (6.6 ft) in height with a branching, cobwebby stem. The leaves are longest near the base of the plant, approaching 90 centimetres (35 in) in length. They are cut into toothed lobes and covered in spines, particularly along the petiole.

The inflorescence bears one or more flower heads, each up to 3 centimetres (1.2 in) long. The head is lined with sticky, twisted, spiny phyllaries and contains pink to purple flowers. The fruit is an achene a 2–4 millimetres (0.079–0.16 in) long topped with a pappus of about 1.5 centimetres (0.59 in) centimeters.

Varieties

There are two very localized varieties:

  • The rare Cirsium hydrophilum var. hydrophilum, the Suisun thistle, is known from two occurrences in the Suisun Marsh, in the salt marsh habitat of the Delta. It is treated as a federally listed endangered species.[1]
  • The very rare Cirsium hydrophilum var. vaseyi, Mt. Tamalpais thistle or Vasey's thistle, is known from about twenty occurrences on Mount Tamalpais in Marin County, in water seeps on the serpentine soils of the mountain. It is currently not a listed federal or state endangered species. [2]

References

  1. ^ California Native Plant Society: var. hydrophilum
  2. ^ California Native Plant Society: var. vaseyi

External links


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