The
black knapweed is a noxious plant, hiding in fields across the country waiting
for the chance to spread. This weed is out-competing native plants for valuable
nutrients and space. The perennial (lives for more than one or two years) grows
up to 3 feet high with black or brown bracts dominating fields in high
densities. These bracts are tick like in structure looming at the very tops of
the plants. These ticks turn from black to rose and lavender from July to
October giving them an attractive cover in order to avoid destruction (BCGOV,
2011.)
(Photo:
Mark Imhof)
(Black
Knapweed in bloom)
Definition Noxious Plants: These
plants cause environmental or
economic harm or have the potential
to cause such harm. They can also
present risks to human health
(Department of primary industries, 2012)
The reason it spreads
so easily is its woody root crown or by seed. Each plant can seed up to 1000
seeds per year. The plant can colonize new locations by hitching a ride on hay
spread onto farmer’s fields or on the undercarriage of cars (munbotgarden,
2010). This is most likely the method used to enter Newfoundland from
previously colonized locations further west. This plant colonizes well in
disturbed areas such as fire and logging locations. Many locations in Newfoundland
that have black Knapweed in high densities are highly disturbed areas such as
the large population in Pippy Park located in St John’s Newfoundland. This area
is an open field previously used as the lawn of a home, it is now unattended.
There is little studied in Canada on this
particular species. But unlike the Black Knotweed there have been significant
studies and remediation efforts towards the Giant Hogweed which will be
discussed nest week.
Works Cited
"Black
Knapweed (Centaurea Nigra) (Nox)." Department of Primary Industries and
Department of Sustainability and Environment.. Victorian Resources, 3 Oct.
2011. Web. 29 Feb. 2012.
<http://vro.dpi.vic.gov.au/dpi/vro/vrosite.nsf/pages/weeds_herbs_perennial_black_knapweed>.
"Botanical
Garden | Alternatives to Invasives." Memorial University. Memorial
University Botanical Garden, 2005. Web. 29 Feb. 2012.
<http://www.mun.ca/botgarden/plant_bio/Invasive_Alien_Species/Alternatives_List.php>.
"Department
of Primary Industries." Invasive Plant Classifications -. Victoria
Goverment, 13 Sept. 2011. Web. 29 Feb. 2012.
<http://www.dpi.vic.gov.au/agriculture/pests-diseases-and-weeds/weeds/invasive-plants>.
"Invasive
Plants with Biocontrol." Invasive Plants with Biocontrol. BC
Ministry of Forest, Lands and Natural Resource Operations. Web. 29 Feb. 2012.
<http://www.for.gov.bc.ca/hra/plants/biocontrol/bcmatrix.htm>.
Who would have thought something so beautiful could be so destructive?!
ReplyDeleteWhat harms does the knotweed plant pose to human health?
- Shane & Asfa
There have been no published effects on human health since the plant has no burs or spines and is non-toxic to humans. There seems to be little chance of there being a negative effect on human health. Please reference the website below. http://vro.dpi.vic.gov.au/dpi/vro/vrosite.nsf/pages/impact_black_knapweed
DeleteAre these the plants that if you pull one one the purple pedals out (assuming they are pedals)you can get nectar? And if it is, would they also have been transported to Canada by bee farmers because they are so rich in nectar that bees love them and when farming bees it is very important to keep them happy so they don't leave their hive. So could that be another reason they became introduced?
ReplyDeleteThanks, Amanda and Morgan.
The plant you are most likely referring to is the red clover. It is highly important for nectar production needed by bees to make honey. The knapweed isn't high in nectar production and therefore is unlikely to have been shipped in for honey production. Check out the link below for more information on the different types of clover important for bees.
Deletehttp://beekeepinghowtosecrets.com/flowers-for-bees/
Sorry but can't seem to view your first figure! Have you looked at some of the studies done in North American on its invasive nature? Lots of research both in agricultural systems and in natural systems - some of the research is done right on the island of Newfoundland!
ReplyDeleteWe did look into a study conducted in British Columbia yet we did not find any studies in NL itself. Yet any links or information you may know about would be greatly appreciated.
DeleteAnd nice touch with the pic of Brittany!
ReplyDelete