|
|
Ontario Weeds: Poison ivy
| Author: |
OMAFRA Staff
|
| Creation Date: |
01 June
2000
|
| Last Reviewed: |
01 November
2003
|
Table of Contents
- Name
- Other Names
- Family
- General Description
- Stems and Roots
- Flowers and Fruit
- Habitat
- Similar Species
- Caution
- Related Links
Name: Poison-ivy, Rhus radicans
L.,
Other Names: herbe à la puce, sumac
vénéneux, sumac grimpant, bois de chien; incorrectly
called Poison-oak which is Rhus toxicodendron L. and does not
occur in eastern Canada
Family: Cashew Family (Anacardiaceae)
General Description: Perennial, spreading
by seed and by woody rhizomes (underground stems) which produce dense
patches.
| Top of Page |
Photos and Pictures
|
Poison ivy. A. Low-growing form with short erect stem
and a flower cluster form the axil of 1 compound leaf. B
Cluster of dry white, berry-like fruits produced from the
flower cluster.
|
C-E. Variation in margin and lobing of leaflets. |
| Top of Page |
Stems & Roots: Stems woody and
of two kinds, the most frequent kind growing horizontally on or just
below the ground surface with upright leafy stalks 10-80 cm (4-32
in.) high; the second kind is a climbing vine which develops aerial
roots and may climb 6-10 m per node, compound, each compound leaf
consisting of 3 leaflets at the tip of a long leafstalk (petiole);
the middle leaflet has a longer stalk than the 2 side leaflets; overall
leaflet shape and type of toothing highly variable between leaflets
on the same stem, as well as among plants within a patch and between
patches; leaflets ranging from narrow to broadly ovate with a smooth
margin, to a few scattered, shallow, rounded teeth, to several, coarse,
deep-pointed teeth which give the leaflet a lobed appearance; leaves
purplish to reddish when unfolding in spring (May to early June),
bright green and often shiny (with a varnished appearance) in summer
and turning a vivid orange-red to wine-red in autumn in sunny areas,
but often lacking the bright colour in shaded places; leaflet smooth
and hairless on both surfaces except for small tufts of brownish hair
on the underside along the mid-vein and in the angles formed by the
mid-vein and some of the lower branching veins.
Flowers & Fruit: Flowers small,
white or greenish, with 5 sepals and 5 petals, in branching clusters
from the leaf axils (angles between leafstalk and stem); flower clusters
inconspicuous because they are often hidden below the dense leaf canopy
and because many plants do not flower every year; each flower in the
cluster followed by a whitish to dull greenish-yellow, dry, berry-like
fruit about 5 mm (1/5 in.) in diameter with lengthwise ridges and
somewhat resembling a peeled orange. Flowers in June and July; berries
produced by September but often remaining on the low leafless stems
all winter.
Habitat: Poison-ivy occurs under forests,
in edges of woodland, meadows, waste areas, fence lines, and roadsides
throughout most of Ontario south of a line from North Bay to Kenora.
The tall climbing vine form, however, is mainly confined to the counties
bordering Lake Erie, Lake Ontario and the lower Ottawa Valley.
| Top of Page |
Similar Species: It is distinguished
by its low growth or its occasional climbing habit, its 3 leaflets
in each compound leaf, its leaves deep green in summer, reddish in
spring and fall, its clusters of whitish to greenish-yellow berries,
and its short, erect, leafless stems which frequently retain a few
berries all winter long. Poison-ivy is sometimes mistakenly called
Poison-oak because some plants have very coarsely toothed or lobed
leaflets. The true Poison-oak, Rhus toxicodendron L. (not illustrated)
[TOXQU] occurs in the southern United States, but not in Canada.
| Caution: All parts of Poison-ivy,
including the roots, contain a poisonous substance which causes
an irritating inflammation of the skin of most people, the inflamed
areas frequently developing blisters and accompanied by intense
itchiness. The poisonous substance is an oily resin contained
in the juice of the plant. Contact with any broken part of the
plant, with leaves which have been chewed by insects, or with
shoes, clothing, implements, or pets which have touched broken
parts of the plant may cause a person with sensitive skin to react.
Dry twigs in winter or dug-up roots in summer can often cause
a reaction. Burning Poison-ivy leaves and stems releases the poison
in the form of tiny droplets on particles of ash and dust in the
smoke, and can cause a severe reaction on exposed skin and in
the breathing passages if a sensitive person breathes or passes
through the smoke of such a fire. The author had a severe reaction
on his arms and legs after trimming a specimen plant with hand
clippers. Although the plant parts never touched his clothes,
it seems that microscopic oil droplets may have squirted out while
cutting the stems and vines and penetrated the cotton of his trouser
legs and shirt sleeves. In cases of suspected contact with the
plant, washing the skin and clothing with a strong soap may not
prevent a reaction but it will help minimize reinfection to other
parts of the body or to other individuals. If a reaction does
develop, one should seek the advice of a physician for proper
treatment. Poison-ivy is designated as a noxious weed by the Province
of Ontario, and it is the duty of every person in possession of
infested land to destroy noxious weeds thereon. |
| Top of Page |
Related Links
... on general Weed
topics
... on weed identification, order OMAFRA Publication 505: Ontario Weeds
... on weed control, order OMAFRA Publication 75: Guide To Weed Control
| Back
to the Ontario Weeds Gallery | Top of Page
|
For more information:
Toll Free: 1-877-424-1300
Local: (519) 826-4047
E-mail: ag.info.omafra@ontario.ca
|
This site is maintained
by the Government of Ontario 
Queen's Printer for Ontario
