Ontario Weeds: Water parsnip

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Excerpt from Publication 505, Ontario Weeds, Order this publication

Table of Contents

  1. Name
  2. Other Names
  3. Family
  4. General Description
  5. Stems and Roots
  6. Leaves
  7. Flowers and Fruit
  8. Habitat
  9. Similar Species
  10. Caution
  11. Related Links

Name: Water-parsnip, Sium suave Walt.,

Other Names: berle douce, berle à larges feuilles

Family: Carrot Or Parsley Family (Umbelliferae)

General Description: Perennial, reproducing only by seed. Roots coarsely fibrous or cord-like (A) but never tuberous.

Photos and Pictures

Water parsnip.

Water parsnip. A.Base of plant.
Water parsnip.
A.Base of plant.

B. Top of flowering stem. C. Much dissected submerged leaf.
B. Top of flowering stem. C. Much dissected submerged leaf.

Stems & Roots: Roots coarsely fibrous or cord-like but never tuberous. Stems erect, 60-200cm (2-6½ft) high, branching above, hollow except for a partition at each node.

Leaves: Leaves alternate (1 per node), pinnately compound with usually 5 to 15 leaflets, these arranged in 2 to 7 pairs of opposite leaflets along the leaf axis (rachis) plus 1 terminal leaflet, the base of the leafstalk broad, thin-winged and encircling the stem at the node, leaflets variable in shape from very narrow and linear to lance-shaped but always sharply saw-toothed; basal leaves growing submerged in water are 2 or more times pinnately divided and quite unlike the stem leaves which grow above the water surface.

Flowers & Fruit: Flowers individually very small, white, in compound umbels [1 large umbel made up of several small umbels] varying 3-12cm (1¼-4½in.) across, with several, narrow, pointed bracts at the base of each large umbel; fruits (pairs of "seeds") oval, 2-3mm (1/12-1/8in.) long. Flowers from July to September.

Habitat: Water-parsnip is a native plant throughout Ontario and grows in low wet areas, often in standing water as deep as 1m (40in.). Water-parsnip has been reported to be poisonous to livestock and, although experimental feeding trials have not proven it to be harmful, livestock growers should be cautioned against the potential danger of this native plant.

Similar Species: It is distinguished from Water-hemlock, known to be very poisonous, by its stem leaves above the water surface being once-pinnately compound, its several thin bracts at the base of each compound umbel, its numerous thin or cord-like roots at the base of each stem, and by the absence of well-defined cross-partitions in the base of the stem which are characteristic of Spotted water-hemlock.

Caution: Circumstantial evidence suggests that Water-parsnip may be poisonous to hogs and cattle so it must be regarded with suspicion. 

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

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