By: Jane Langille
Summer weather means more chances to explore the great outdoors and exercise your green thumbs in the garden. But some plants can hurt your skin, just by touching them. Here are three hazardous plants you’ll want to avoid:
1. Giant Hogweed
For the last five years, municipalities across Canada have been alerting residents to the dangers of giant hogweed. The plant produces a toxic sap that can cause burning blisters when the skin that has come into contact with the sap is exposed to sunshine.
Giant hogweed has several distinguishing features:
- it’s very tall, reaching 2.5 – 4.0 metres in height
- leaves are large, up to 1 metre in breadth and sharply lobed
- the stem has reddish-purple blotches
- the flower heads are huge white clusters up to a metre wide1
Cow parsnip, which also has sap that can cause severe skin reactions, is often mistaken for giant hogweed; however, it is much smaller and does not have a purple blotchy stem. Check out this short video by the Invasive Species Council of Metro Vancouver or read this story to learn how to tell the difference. Eradication efforts have been very successful in the last five years, but if you do spot giant hogweed, notify your local municipality or conservation authority.
2. Stinging Nettle
After weeding his cottage garden, a friend of mine earned a nasty rash on his arms and hands from coming into contact with stinging nettle. Its stem and leaves have tiny hairs that can penetrate the skin and break off easily, injecting an irritating fluid under the skin. This causes an itchy rash, red swelling and numbness. A reaction from the first contact can last a few minutes, but repeated contact can cause pain that lasts for days.
Stinging nettle is found across Canada and grows anywhere from a half a metre to just over a metre in height. Surprisingly, nettles can be eaten, but precautions including picking the leaves while wearing gloves and boiling them to destroy the irritating substance are necessary. Stinging nettle is also used as an herbal remedy for a variety of health conditions, but the scientific evidence is weak so the effectiveness is highly questionable.2 After his bad skin reaction, my friend is in no hurry to add stinging nettles to his menu anytime soon. He removed the clump of plants wearing gloves and head-to-toe clothing.
3. Poison Ivy
Poison ivy is found everywhere in Canada except Newfoundland, growing in sandy, stony or rocky areas along shores, borders of woods or roadsides. All parts of the plant from the leaves to the roots contain a poisonous sap that can cause an intensely itchy skin reaction that begins 24-48 hours after contact and can progress to inflamed blisters.
Poison ivy has these distinguishing features: 3
- the leaves grow in a group of three pointed leaflets, which can be smooth or tooth-edged
- the leaves are reddish in the spring, turn green in the summer and can be yellow, orange or red in the fall
- the plant stems are woody
- the most common form is a trailing vine, with upright leafy stalks 10-80 cm in length
- the second kind is a vine that can grow 6-10 metres up trees, posts or rough surfaces
Poison ivy is often mistaken for poison oak or poison sumac, which can also cause skin rashes from their sap. Read more to learn how to recognize poison ivy, oak and sumac.
If you have come into contact with any of these plants, wash the area with soap and water to remove the sap and see your doctor for treatment.