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Weed Identification

purple loosestrife

Family

Lythraceae

Scientific Name

Lythrum salicaria

Other Common Names:

purple lythrum
rainbow weed
salicaire
spiked loosestrife

Habit

Seedlings have ovate hairless cotyledons 3-6 mm long and 2-3 mm wide. Mature plants reach heights of 50-150 cm tall and arise from thick fleshy roots. Stems have several branches covered with soft hairs and are capable of spreading by bits of stem, root and seed.

Leaves

Leaves slightly hairy are lance shaped and can be opposite or in whorls of 3.

Identifying Characteristics

Found in moist places, purple flowers, and opposite leaves.

Flower Seed Head

Flowers appear in spikes on the end of branches and are purple with 5-7 petals, 7-10 mm long.

Seed Fruit

Fruit are 2 chambered capsules containing several seeds. A single plant can produce as many 2 million seeds a year.

Where Found

Found throughout the northeastern United States this plant can destroy wetlands taking the place of native vegetation. This species is a problem for cranberry bogs, spring flooded pastures, ditches, canals, and roadsides.

Growth Habit

upright and nonwoody

Thorns or Spines

not present

Approximate Flower Diameter

dime

Dominant Flower Color

Varies: 
purple
red

Flower Symmetry

radial symmetery

Leaf Hairs

Varies: 
has hairs
no hairs

Leaf Shape

Varies: 
heart
needle
lance
oval

Leaf Arrangement

Varies: 
alternate
opposite
whorled

Leaf Margin

entire

Leaf Structure

simple

Leaf Stalk

none

Stem Hairs

Varies: 
has hairs
no hairs

Stem Cross Section

round or oval

Milky Sap

not present

Root Structure

taproot

Life Cycle

perennial

Plant Type

Herb