Cirsium hillii
Encyclopedia
Cirsium pumilum var. hillii is a type of thistle
endemic to North America
. The common name for this plant is Hill’s thistle (ITIS, 2011). Alternate names for this plant include Cirsium hillii and Cirsium pumilum subsp. hillii (ITIS, 2011).
usually reaching 25 to 60 cm in height, with a taproot
system that runs deep into the ground (Allen, 2004). It is a perennial plant
usually living for three years, and flower
s in July and August (Allen, 2004). The plant’s leaves
are an elliptic-oblong shape with serrated edges, have tiny prickle
s, and have one central vein
with smaller veins branching from it (Molano-Flores, 2000).
The top of the stem holds a composite flower head, each consisting of many individual flowers (Molano-Flores, 2000). The flowers of this plant are usually purple
in color (Allen, 2004). Hill's thistle tends to looks very similar to Cirsium vulgaris during its seedling and rosette stages; one can easily be mistaken for the other (Molano-Flores, 2000).
and areas lacking tall vegetation (Allen, 2004). Its preferred habitats include sand prairie
s, sand dunes, open wooded areas, and limestone plains with thin soil and little vegetation (Allen, 2004). Natural fires are important because they burn large trees and debris, which reduces competition and allows Cirsium hillii to grow (Allen, 2004).
and the United States
(Allen, 2004). It is found around the Great Lakes, in the southern part of Ontario
, as well as Michigan
, Wisconsin
, Minnesota
, Iowa
, Illinois
and Indiana
(Allen, 2004).
Hill's thistle generally only lives to be 2 or 3 years old, typically flowering at 3 years (Allen, 2004). This could pose a problem in terms of conservation because, if fewer plants survive to the flowering stage at the end of their life, there will be less production of offspring.
Lack of disturbance by natural fires is another reason why Hill's thistle is threatened (Allen, 2004). This plant needs an open, dry, grassy environment in order to thrive (Allen, 2004). Areas where it previously succeeded are now managed to prevent fires, allowing the invasion of shrubs and trees, which outcompete the open-habitat species (Freeland et al, 2010).
Hill's thistle is a rare species found in relatively few places around the globe and thus ongoing conservation efforts are essential for its survival (Freeland et al, 2010). Suggestions for the conservation of this species include reducing shoreline development and aggregate demand in its habitat (Allen, 2004). Conservation efforts should also focus determining how management of fires affects seedling establishment and what can be done in regards to fire reduction (Higman and Penskar, 1996).
Thistle
Thistle is the common name of a group of flowering plants characterised by leaves with sharp prickles on the margins, mostly in the family Asteraceae. Prickles often occur all over the plant – on surfaces such as those of the stem and flat parts of leaves. These are an adaptation that protects the...
endemic to North America
North America
North America is a continent wholly within the Northern Hemisphere and almost wholly within the Western Hemisphere. It is also considered a northern subcontinent of the Americas...
. The common name for this plant is Hill’s thistle (ITIS, 2011). Alternate names for this plant include Cirsium hillii and Cirsium pumilum subsp. hillii (ITIS, 2011).
Physical description
Hill's Thistle is a low-growing thistleThistle
Thistle is the common name of a group of flowering plants characterised by leaves with sharp prickles on the margins, mostly in the family Asteraceae. Prickles often occur all over the plant – on surfaces such as those of the stem and flat parts of leaves. These are an adaptation that protects the...
usually reaching 25 to 60 cm in height, with a taproot
Taproot
A taproot is an enlarged, somewhat straight to tapering plant root that grows vertically downward. It forms a center from which other roots sprout laterally.Plants with taproots are difficult to transplant...
system that runs deep into the ground (Allen, 2004). It is a perennial plant
Perennial plant
A perennial plant or simply perennial is a plant that lives for more than two years. The term is often used to differentiate a plant from shorter lived annuals and biennials. The term is sometimes misused by commercial gardeners or horticulturalists to describe only herbaceous perennials...
usually living for three years, and flower
Flower
A flower, sometimes known as a bloom or blossom, is the reproductive structure found in flowering plants . The biological function of a flower is to effect reproduction, usually by providing a mechanism for the union of sperm with eggs...
s in July and August (Allen, 2004). The plant’s leaves
Leaves
-History:Vocalist Arnar Gudjonsson was formerly the guitarist with Mower, and he was joined by Hallur Hallsson , Arnar Ólafsson , Bjarni Grímsson , and Andri Ásgrímsson . Late in 2001 they played with Emiliana Torrini and drew early praise from the New York Times...
are an elliptic-oblong shape with serrated edges, have tiny prickle
Prickle
Prickle may refer to:*Prickle , a sharp, needle-like structure*Prickle cell of the skin*Prickle , a planar cell polarity protein*the collective noun for a pack of porcupines*Prickle , a character on The Gumby Show...
s, and have one central vein
Vein
In the circulatory system, veins are blood vessels that carry blood towards the heart. Most veins carry deoxygenated blood from the tissues back to the heart; exceptions are the pulmonary and umbilical veins, both of which carry oxygenated blood to the heart...
with smaller veins branching from it (Molano-Flores, 2000).
The top of the stem holds a composite flower head, each consisting of many individual flowers (Molano-Flores, 2000). The flowers of this plant are usually purple
Purple
Purple is a range of hues of color occurring between red and blue, and is classified as a secondary color as the colors are required to create the shade....
in color (Allen, 2004). Hill's thistle tends to looks very similar to Cirsium vulgaris during its seedling and rosette stages; one can easily be mistaken for the other (Molano-Flores, 2000).
Habitat
Hill's thistle thrives in areas that are open, sandy, and dry. It also grows well in areas that are susceptible to fireFire
Fire is the rapid oxidation of a material in the chemical process of combustion, releasing heat, light, and various reaction products. Slower oxidative processes like rusting or digestion are not included by this definition....
and areas lacking tall vegetation (Allen, 2004). Its preferred habitats include sand prairie
Prairie
Prairies are considered part of the temperate grasslands, savannas, and shrublands biome by ecologists, based on similar temperate climates, moderate rainfall, and grasses, herbs, and shrubs, rather than trees, as the dominant vegetation type...
s, sand dunes, open wooded areas, and limestone plains with thin soil and little vegetation (Allen, 2004). Natural fires are important because they burn large trees and debris, which reduces competition and allows Cirsium hillii to grow (Allen, 2004).
Range
Hill's thistle is an endemic species to North America, found only in CanadaCanada
Canada is a North American country consisting of ten provinces and three territories. Located in the northern part of the continent, it extends from the Atlantic Ocean in the east to the Pacific Ocean in the west, and northward into the Arctic Ocean...
and the United States
United States
The United States of America is a federal constitutional republic comprising fifty states and a federal district...
(Allen, 2004). It is found around the Great Lakes, in the southern part of Ontario
Ontario
Ontario is a province of Canada, located in east-central Canada. It is Canada's most populous province and second largest in total area. It is home to the nation's most populous city, Toronto, and the nation's capital, Ottawa....
, as well as Michigan
Michigan
Michigan is a U.S. state located in the Great Lakes Region of the United States of America. The name Michigan is the French form of the Ojibwa word mishigamaa, meaning "large water" or "large lake"....
, Wisconsin
Wisconsin
Wisconsin is a U.S. state located in the north-central United States and is part of the Midwest. It is bordered by Minnesota to the west, Iowa to the southwest, Illinois to the south, Lake Michigan to the east, Michigan to the northeast, and Lake Superior to the north. Wisconsin's capital is...
, Minnesota
Minnesota
Minnesota is a U.S. state located in the Midwestern United States. The twelfth largest state of the U.S., it is the twenty-first most populous, with 5.3 million residents. Minnesota was carved out of the eastern half of the Minnesota Territory and admitted to the Union as the thirty-second state...
, Iowa
Iowa
Iowa is a state located in the Midwestern United States, an area often referred to as the "American Heartland". It derives its name from the Ioway people, one of the many American Indian tribes that occupied the state at the time of European exploration. Iowa was a part of the French colony of New...
, Illinois
Illinois
Illinois is the fifth-most populous state of the United States of America, and is often noted for being a microcosm of the entire country. With Chicago in the northeast, small industrial cities and great agricultural productivity in central and northern Illinois, and natural resources like coal,...
and Indiana
Indiana
Indiana is a US state, admitted to the United States as the 19th on December 11, 1816. It is located in the Midwestern United States and Great Lakes Region. With 6,483,802 residents, the state is ranked 15th in population and 16th in population density. Indiana is ranked 38th in land area and is...
(Allen, 2004).
Importance to humans and the ecosystem
Hill's thistle is not used for medicine, food, or fibres (Allen, 2004). This lack of utility may be beneficial to its persistence in the wild, as it has been suggested that samples only be collected for scientific reasons (Molano-Flores, 2000). It does, however, play an important role in its ecosystem because it is consumed by whitetail deer (Allen, 2004). Multiple plants grow near Hill's thistle, such as big and little bluestem, blazing star, rough fescue, pale agoseris, juniper, hair grass, western sunflower, and field chickenweed (MNFI, 2007). Because Hill's thistle is one of the first plants to colonize its habitat, perhaps it plays a role in stabilizing the soil and benefits these other plants.Conservation
The Committee of the Status of Endangered Wildlife in Canada last examined Hill's thistle in 2004 and named it as "threatened" due to its “rarity, restricted range, and human factors, which make it susceptible to extinction,” (Allen, 2004). The plant's main threats include aggregate demand, shoreline development, and invasive species (Allen, 2004). Human recreation and development encroachment may also negatively impact Hill's thistle (Allen, 2004).Hill's thistle generally only lives to be 2 or 3 years old, typically flowering at 3 years (Allen, 2004). This could pose a problem in terms of conservation because, if fewer plants survive to the flowering stage at the end of their life, there will be less production of offspring.
Lack of disturbance by natural fires is another reason why Hill's thistle is threatened (Allen, 2004). This plant needs an open, dry, grassy environment in order to thrive (Allen, 2004). Areas where it previously succeeded are now managed to prevent fires, allowing the invasion of shrubs and trees, which outcompete the open-habitat species (Freeland et al, 2010).
Hill's thistle is a rare species found in relatively few places around the globe and thus ongoing conservation efforts are essential for its survival (Freeland et al, 2010). Suggestions for the conservation of this species include reducing shoreline development and aggregate demand in its habitat (Allen, 2004). Conservation efforts should also focus determining how management of fires affects seedling establishment and what can be done in regards to fire reduction (Higman and Penskar, 1996).