Poisonous to Touch Weed Series: Poison Oak (Toxicodendron diversilobum) and (Toxicodendron pubescens)

Pacific Poison Oak (Toxicodendron diversilobum) and Atlantic Poison Oak (Toxicodendron Toxicodendron pubescens) are the only two poisonous to touch plants in this series that do not grow in Canada except for the very south/western tip of British Columbia. They are not nearly as prevalent as poison ivy with Pacific poison oak occurring natively along the pacific coast of the U.S. and Atlantic poison oak occurring … Continue reading Poisonous to Touch Weed Series: Poison Oak (Toxicodendron diversilobum) and (Toxicodendron pubescens)

Poisonous to Touch Weed Series: Poison Sumac (Toxicodendron vernix)

Poison Sumac (Toxicodendron vernix) is a perennial shrub or small tree, native to eastern Canada as well as east-central and eastern United States. Like poison ivy and poison oak the leaves and berries of this plant contain urushiol (an oily mixture of organic chemical compounds); but the oil is said to be more concentrated in poison sumac. The Urushiol can cause a severe allergic reaction in sensitive … Continue reading Poisonous to Touch Weed Series: Poison Sumac (Toxicodendron vernix)

Poisonous to Touch Weed Series: Wild Parsnip (Pastinaca sativa)

Wild parsnip (Pastinaca sativa) aka poisonous parsnip is one of the phototoxic weeds we grow here in Canada. It is a non-native and as such is an aggressive and invasive species. It is the only one of the phototoxic weeds that has a yellow flower, the others bearing white umbels. It’s pinnately compound leaves are also quite different than the palmately compound leaves of cow … Continue reading Poisonous to Touch Weed Series: Wild Parsnip (Pastinaca sativa)

Poisonous to Touch Weed Series: Cow Parsnip (Heracleum maximum)

Cow Parsnip (Heracleum maximum) aka Common Parsnip or American Parsnip, is a native plant that widely grows in north America. It is a large plant rising up to heights of 1-2.5 m (3-8 ft.) when in flower. Like giant hogweed, cow parsnip contains organic chemicals within it’s sap called furanocoumarins. This chemical is activated by ultraviolet radiation and the result is severe burning, blistering and … Continue reading Poisonous to Touch Weed Series: Cow Parsnip (Heracleum maximum)

Poisonous to Touch Weed Series: Giant Hogweed (Heracleum mantegazzianum)

Giant hogweed (Heracleum mantegazzianum) is likely the largest and most dangerous to touch perennial weed in North America. In Ontario it commonly reaches heights of 3-4.5m but in other parts of the world it can reach heights of 5.5m (MacDonald F. and Anderson H. 2012). There are a few other Giant Hogweed species that are a bit smaller in size but Heracleum mantegazzianum is the … Continue reading Poisonous to Touch Weed Series: Giant Hogweed (Heracleum mantegazzianum)

Poisonous to Touch Weed Series: Poison Ivy (Toxicodendron radicans and Toxicodendron Rydbergii)

By: Kimberley Pacholko Eastern Poison Ivy, (Toxicodendron radicans) and Western Poison Ivy (Toxicodendron Rydbergii ) are important plants to learn how to identify for personal safety. Touching any part of this plant can cause a painful itchy rash with red swollen skin and painful blisters. I have had the miss fortune of being caught twice by this plant and can testify to how unpleasant the … Continue reading Poisonous to Touch Weed Series: Poison Ivy (Toxicodendron radicans and Toxicodendron Rydbergii)