Heracleum mantegazzianum, or giant hogweed, spreads easily and is poisonous. (CBC)

An invasive and toxic plant is creeping across Nova Scotia. Heracleum mantegazzianum, or giant hogweed, spreads easily and is poisonous.

The plant can be identified by its purple-speckled stem and by its sheer size, often growing more than four metres high.

Experts say the sap can cause blisters, burning and even blindness.

"It's dangerous enough that you don't want to handle any part of the plant with your bare hands, nor do you want to try removing this plant if it's on your property," said Marian Munro, curator of botany at the Nova Scotia Museum.

The plant is most easily identified by the purple colour on its stem. (CBC)

Munro said the sap causes what is known as phyto-photosensitivity.

"Aside from the irritant qualities of the sap within the plant, apparently for up to six years after contact it can affect your skin every time you're in the sun."

The weed is originally from Asia and was first identified in Cape Breton in 1980. It has since been spotted in Truro, Bridgewater and Halifax.

Munro advises homeowners who see the plant in their yards to call a landscaper to have it removed.