Plants You Don't Want to Touch!

Here are three of the many plants that are best left alone - many people have discovered this the hard way, suffering from itchy, oozy skin blistering and rashes, that often require medical attention.

1. Poison Ivy (Rhus radicans)

   Likely the most common and familiar of these three plants, poison ivy is widespread throughout Ontario in forests, fencerows, meadows, roadsides and natural areas.

   Plant form: Grows in patches on the ground, or climbs fences, trees or buildings. The tall climbing form is mainly confined to areas along Lakes Erie, Ontario and the lower Ottawa valley

   Life cycle: Perennial, spread by seeds (dispersed by birds) and by underground woody rhizomes. Stems also root in contact with soil.

   Appearance: A deciduous woody vine with 3 leaflets (hence the saying "Leaves of three - let it be"). The longer petiolule on the centre leaf is an identifying characteristic. Leaves are shiny green all summer, turning bright red in the fall. Clusters of white berries are produced by late summer and may be retained on the stems all winter.

   Caution: All plant parts are poisonous, including roots, stems and leaves. The oil resin may be released onto clothes, pets, or prunings. Sensitive individuals need to use extreme care year-round. Inhaling smoke from burning plants can cause severe reactions in breathing passages.

   May be confused with: Fragrant sumac - which has 3 leaflets, but no extended middle petiolule; Virginia creeper - which has 5 leaflets instead of 3; Poison oak - which is not found in Ontario (New Jersey and south), which has more coarsely lobed leaves more like an oak.

   

   Poison Ivy - 3 leaflets

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   Poison ivy up a tree

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2. Giant Hogweed (Heracleum mantegassianum)

   This member of the Carrot family has gained notoriety from recent reports in the media. It's a distinctive looking plant in the landscape now as a mature plant along roadsides, streambanks, and waste areas. Giant hogweed has been reported in Norfolk, Wellington, and Simcoe counties and the Muskoka region.

   Plant form: Tall plants usually 2 - 5m in height. It's been described as a wild carrot on steroids.

   Life cycle: Biennial or perennial, flowering only once in its lifetime and reproducing only by seed.

   Appearance: Rosettes up to 1 m tall grow the first year, and in the 2nd year, either grow a larger rosette (up to 2m), or produce a flower stalk up to 5 m tall, with a hollow reddish- urple stem up to 10 cm in diameter. Flowers from June to September, with a compound umbel up to 1.2 m across, with 30 to 50 branches, each with an umbel with 30-20 flowers.

   Caution: Giant hogweed contains furocoumarins (psoralens), which make human skin hypersensitive to sunlight, causing cellular damage at the surface. They absorb long-wave ultraviolet light and become photodynamic. Pets can also carry the oils on their fur.

   May be confused with: Angelica - also tall growing (2.5m) with thick purple stems and compound umbels - or - spotted water hemlock, also tall growing (2m) with hollow stems and large umbels, but more slender leaves (and a very poisonous plant) - but giant hogweed is much larger than either of these plants.

   

   Close up of immature seed head

   

   Flower

   

   Leaf close-up

   

   Large leaf

   

   Hollow stem

   

   Canopy

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3. Wild parsnip (Pastinaca sativa)

   Another member of the Carrot family, this wild plant is very similar to cultivated parsnip, and may have actually escaped from fields. Wild parsnip occurs throughout Ontario on roadsides, meadows, fencerows and abandoned fields.

   Plant form: Medium plants usually 0.5 to 1.5m in height. The whole plant has a distinctive parsnip odour.

   Life cycle: Biennial, reproducing only by seed. Seedling rosettes have ovate leaves on long stems, but change to compound leaves with broad leaflets. The flower stems bolt from May to late autumn.

   Appearance: A highly branched plant, with hollow green stems. The compound leaves, similar to parsnip, are green & dense growing. The yellow flowers are held high above the leaves, clustered in compound umbels up to 20 cm across.

   Caution: Similar to giant hogweed, wild parsnip also contains furocoumarins which can cause severe skin dermatitis, when activated by sunlight. Surprisingly, the root of this plant is edible, but large quantities should be avoided - and be cautious about the peelings!

   May be confused with: Other members of the Carrot family, like cow-parsnip (which has white flowers in umbels, but large broad leaflets, not pinnate like wild parsnip - and which is not poisonous), or poison hemlock (which has finely divided leaves, and small compact umbels - and is highly poisonous). Look for pinnate leaves, yellow flowers and distinctive odour in wild parsnip.

   

   Wild parsnip - Flower

   

   Wild parsnip - Leaf

   

   Wild parsnip - Root

   

   Wild Parnsip in a ditch

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