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On the Down the Garden Path Podcast, landscape designer Joanne Shaw discusses down-to-earth tips and advice for your plants, gardens, and landscapes. She believes it's important and possible to have great gardens that are low maintenance.

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Jul 11, 2022

With summer well underway and many of us heading off to the cottage or to spend some time out in nature, Joanne and Matt help you identify some of the harmful plants you might find during your travels. In this episode of the Down the Garden Path podcast, they discuss poisonous plants.

Join Joanne and Matt as they discuss poisonous plants.

What are the common harmful plants when camping and hiking?

  • Poison Ivy

Poison Ivy Dermatitis Causes

  • Poison ivy, poison oak, and poison sumac plants contain a compound called urushiol, which is a light, colourless oil that is found in the fruit, leaves, stem, roots, and sap of the plant. When urushiol is exposed to air, it turns brown and then black; plant leaves develop small black spots.
  • There are several ways that you can be exposed to urushiol:
    • By touching the sap or rubbing against the leaves of the toxic plant at any time of year
    • By touching something that has urushiol on it, such as animal fur or garden tools
    • By breathing in smoke when toxic plants are burned

After contact with urushiol, approximately 50 percent of people develop signs and symptoms of poison ivy dermatitis. The symptoms and severity differ from person to person.

The most common signs and symptoms of poison ivy dermatitis are:

  • Intense itching
  • Skin swelling and blisters
  • Skin redness

These symptoms usually develop within four hours to four days after exposure to the urushiol. After the initial symptoms, allergic individuals develop fluid-filled blisters in a line or streak-like pattern. The symptoms are worse within 1 to 14 days after touching the plant, but they can develop up to 21 days later if one has never been exposed to urushiol before.

The blisters can occur at different times in different people; blisters can develop on the arms several days after blisters on the hands developed. This does not mean that the reaction is spreading from one area of the body to the other. The fluid that leaks from blisters does not spread the rash. Poison ivy dermatitis is not contagious and cannot be passed from person to person. However, urushiol can be carried under fingernails and on clothes; if another person comes in contact with the urushiol, they can develop poison ivy dermatitis.

  • Poison Sumac: Poison Oak and Poison Sumac.
    • Appearance: 10 to 15 ft tree
    • Where they can be found: Wet woodland area, moist acidic areas
    • How they grow
    • How to be safe around them

Other poisonous plants mentioned by listeners on the podcast:

  • Giant Hog Weed
  • Stinging Nettle
  • Water Hemlock
  • Night Shade
  • Ornamental Plants like Angels Trumpet and Castor Bean Plant

Any treatment mentioned during the show is not medical advice and is based on the personal experience of Joanne, Matthew, and their listeners of the podcast. If you encounter any of the plants mentioned during the show, please seek professional medical attention immediately! In case of an emergency, call 9-1-1.

Source: UpToDate and Poisonous Plants by F. Stary, Z. Berger

Each week on Down The Garden Path, professional landscape designers Joanne Shaw and Matthew Dressing discuss down-to-earth tips and advice for your plants, gardens and landscapes.

As the owner of Down2Earth Landscape Design, Joanne Shaw has been designing beautiful gardens for homeowners east of Toronto for over a decade. A horticulturist and landscape designer, Matthew Dressing owns Natural Affinity Garden Design, a landscape design and garden maintenance firm servicing Toronto and the Eastern GTA. Together, they do their best to bring you interesting, relevant and useful topics to help you keep your garden as low maintenance as possible. In their new book, Down the Garden Path: A Step-By-Step Guide to Your Ontario Garden, Joanne and Matthew distill their horticultural and design expertise and their combined experiences in helping others create and maintain thriving gardens into one easy-to-read monthly reference guide. It's now available on Amazon.