Ontario Weeds: Purple loosestrife

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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: Purple loosestrife, Lythrum salicaria L.,

Other Names: salicaire, Spiked loosestrife, salicaire commune, lythrum salicairel

Family: Loosestrife Family (Lythraceae)

General Description: Perennial, reproducing only by seed.

Photos and Pictures

Purple loosestrife (A - flowering spikes; B - a typical strand).
Purple loosestrife (A - flowering spikes; B - a typical strand).

Purple loosestrife.
Purple loosestrife.

Stems & Roots: Stems tall, erect, 60-120cm (24-48in.) high, somewhat branched, usually finely hairy, more or less square in cross-section, especially where the leaves are opposite; leaves opposite (2 per node) or sometimes whorled (3 or more per node), stalkless, broad near the base and tapering towards the tip, 3-10cm (1¼-4in.) long, finely hairy; upper leaves and those in the inflorescence usually alternate (1 per node) and smaller than the lower ones.

Flowers & Fruit: Flowers in dense terminal spikes; sepals united into a column with 8 to 10 or 12 prominent green veins and ending in several, long, thin, pointed lobes; petals 5 to 7, red-purple, 7-10mm (¼-2/5in.) long, very showy; stamens several and 1 pistil; seedpod small, containing many tiny seeds. Flowers from June to autumn.

Habitat: Purple loosestrife was introduced from Europe but is now widely naturalized in wet meadows, river flood-plains, and damp roadsides throughout most of Ontario.

Similar Species: Its opposite leaves and square stems resemble plants of the Mint Family but it is distinguished by having separate petals, a seedpod with many fine seeds, and it lacks the minty odour.

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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