T.E.R:R.A.I.N - Taranaki Educational Resource: Research, Analysis and Information Network

Cirsium arvense (Californian Thistle)

Kingdom: Plantae
Order: Asterales
Family: Asteraceae
Tribe: Cynareae
Genus: Cirsium
Species: C.arvense
Scientific name: Cirsium arvense
Common name: Californian thistle, Cali.

Cirsium arvense is a tall herbaceous perennial plant, common on roadsides, rough ground and grassland. Its flowerheads are fragrant and involucre purplish and they haves diameter a 2 cm. Its leaves are spiny and the stem spineless. Separate male and female flowerheads, the male ones having more spherical involucres.
This is one of the most common thistle species in New Zealand. It is very troublesome in pastures because it is so difficult to control. Once a plant has established in a pasture, it forms a patch of plants which are initially connected by the creeping root system called rhizome, but these connections rot away in time. These patches of thistles eventually get larger over time if conditions are suitable for its growth. Every winter, the foliage dies off, but the creeping root system is still alive underground. New plants re-establish from these roots in spring, and flowering occurs in summer and autumn.
The control of these thistles is a step closer as it is the host specificity of green thistle beetle, Cassida rubiginosa  
and Californian thistle stem borer Apion onopordi a potential control agent for Californian.thistle.

New science confirms best Cali kill is when it is cut wet:


Discharging windblown seeds

Mature leaves.

Thanks to Wikipedia for text and information: https://creativecommons.org/licenses/by-sa/3.0/