Giant Hogweed

HISTORY Giant hogweed originally came from Asia. It was introduced to North America as an ornamental garden plant. It is now found in many provinces throughout Canada, as well as a number of US states. There are only a couple of known sites on PEI, and all are contained within private gardens. IDENTIFICATION Giant hogweed has several look-a-likes that grow in PEI, including: cow parsnip, woodland angelica, and Queen Anne’s…

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HISTORY

CONCERN Giant hogweed can have negative impacts on both the environment and human health. It is able to outcompete native plants by monopolizing the light supply with its broad leaves and tall stem. The sap of giant hogweed can cause severe photodermititis in humans. Contact with the sap on skin, coupled with exposure to UV rays, can cause burning and blistering. The affected area may take months to fully heal,…

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Black Knapweed (Centaurea nigra)

Black Knapweed is a perennial plant native to the Meditarranean, but is also naturalized throughout Europe.  Black Knapweed was first introduced to North America in the early 1900s as an ornamental species, and is now present is most Canadian provinces.  It tolerates a wide range of conditions and habitats, however it grows best in disturbed, well-drained soils and full sun.  It’s a member of the Aster family. IDENTIFICATION Here are…

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Blackthorn (Prunus spinosa)

Blackthorn is a small, deciduous shrubby tree.  It grows best in moist, well drained soils and full sun.  It is native to most of Europe, the UK and Western Asia.  It is often referred to as “sloe”.  It has a native lookalike on PEI, Hawthorn (Crataegus spp.).  However, blackthorn spines have buds growing along their length while hawthorn does not.  Blackthorn also starts producing flowers before its leaves are out,…

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Cypress Spurge (Euphorbia cyparissias)

Cypress spurge is a herbaceous perennial plant.  It grows in open, disturbed areas such as pastures, abandoned fields, ditches and coastal areas. IDENTIFICATION Here are some key features that may help to positively identify cypress spurge: Can grow to 10-40cm tall Leaves are small, linear-shaped, 1-3cm long and 1-3mm wide, whorled around the stem True flowers lack petals, sepals Greenish-yellow heart-shaped bracts under flower Flowers turn to purple-red as they…

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Canada Waterweed (Elodea canadensis)

Canada waterweed is an underwater perennial.  It grows in dense mats in clear waters.  Most people know it as an aquarium plant.  It is considered native to Nova Scotia and New Brunswick, but outcompetes native pond weeds in Island waterbodies.  Canada waterweed was first detected in PEI at Knox’s Damn, Head of Montague, in 2005, and since then in Pondside Park, Stratford. IDENTIFICATION Here are some key features that may…

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Common Reed Grass (Phragmites australis ssp. australis)

Common reed grass (Phragmites australis ssp. australis) is an invasive perennial grass that is native to Eurasia.  It is not known for certain how it was moved to North America, but it likely arrived on the Atlantic coast accidentally via ballast materials in the late 1700s – early 1800s.  (Swearingen, J. and K. Saltonstall. 2010) Since establishing in North America, Phragmites australis ssp. australis has spread throughout continental U.S. and to most…

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