Ontario Weeds: Purple loosestrife

Table of Contents

1. Name
2. Other Names
3. Family
4. General Description
   • Photos and Pictures
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.

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Photos and Pictures

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

Purple loosestrife.

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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.

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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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