Ontario Weeds: Leafy spurge

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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. Flowers and Fruit
  7. Habitat
  8. Similar Species
  9. Related Links

Name: Leafy spurge, Euphorbia esula complex*

Other Names: euphorbe ésule, euphorbe feuillue

Family: Spurge Family (Euphorbiaceae)

General Description: Perennial, reproducing by seed and by widely spreading underground roots having numerous small pinkish buds from which new leafy shoots are produced.

Photos and Pictures

Leafy spurge (A - plant; B - portion of inflorescence showing cyathia between pairs of bracts).
Leafy spurge
(A - plant; B - portion of inflorescence showing cyathia between pairs of bracts).

Leafy spurge. A. Top of flowering plant. B. Detail of a portion of the inflorescence showing 2 oval bracts (e), each with a small branch in its axil and between the branches is 1 cyathium consisting of a cup (h) with U-shaped glands (j) and tiny lobes (k) on its rim and showing 3 male flowers (f) (3 single stamens) and 1 female flower (g) (1 single pistil) that have emerged from inside it.
Leafy spurge.
A. Top of flowering plant. B. Detail of a portion of the inflorescence showing 2 oval bracts (e), each with a small branch in its axil and between the branches is 1 cyathium consisting of a cup (h) with U-shaped glands (j) and tiny lobes (k) on its rim and showing 3 male flowers (f) (3 single stamens) and 1 female flower (g) (1 single pistil) that have emerged from inside it.

Stems & Roots: Similar to Cypress spurge but taller and coarser. Stems erect, up to 1m (40in.) high; leaves numerous, alternate (1 per node), or crowded and some appearing opposite (2 per node), 3-7cm (1¼-3in.) long, linear or wedge-shaped, and 1 whorl of 7 or more leaves at the tip of the stem; inflorescence greenish, consisting of a large umbel-like cluster of 7 or more branches at the tip of the main stem and smaller branching clusters at the ends of these and other branches below the main umbel; leaves (bracts) of the inflorescence very broadly ovate to almost kidney-shaped and usually abruptly tipped with a very fine point.

Flowers & Fruit: Flowers tiny, unisexual and very unusual; several male (pollen-producing) flowers consisting only of single, tiny stamens without sepals or petals, and 1 female (seed-producing) flower consisting only of a single pistil also without sepals or petals crowded in a cup-like structure, the rim of which has 4 yellowish U-shaped glands and 4 tiny lobes, the whole complex of several tiny male and one female flowers in a cup being called a cyathium; seedpods 3-lobed, containing 3 seeds about 2.5mm (1/10in.) long, smooth, grayish to yellowish or brownish and usually with a tiny yellow bump near the base; the seedpods exploding when dry and throwing the seeds several metres in all directions. The plants are deep green to almost bluish-green during spring, changing to yellowish-green or olive-green at flowering time during June and July, and changing back to a dull green or sometimes reddish-green after flowering; then sometimes with a secondary period of flowering in late August or September, shedding seeds while still flowering.

Habitat: Leafy spurge occurs in several localities throughout Ontario, occupying a wide variety of soils and habitats, including cultivated land, meadows, pastures, waste places, open woodland, roadsides, and gardens.

Similar Species: It is distinguished from most other plants by having milky juice, spreading roots with pink buds, its slender green leaves that are mostly alternate, and its yellowish-green inflorescence, and from Cypress spurge by its taller, coarser habit, longer leaves, and fewer branches in the main umbel at the tip of the stem. It is distinguished from the annual erect spurges by its perennial habit, and tall, coarse stems with mostly linear leaves.

*There is still considerable confusion about the botanical name for the Leafy spurge that grows in North America. What is called Leafy spurge is actually a complex of several closely related groups of plants which seem to have physiological differences but are very similar in appearance. Insects and disease organisms can tell the difference even though people cannot! The names E. virgata and E. x pseudovirgata are also being used for this complex in current literature.

 

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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