Weed Seed - Sessile joyweed (Alternanthera sessilis)

Invasive Plant - Sessile joyweed (Alternanthera sessilis)

Family

Amaranthaceae

Synonyms

Achyranthes sessilis

Distribution in Canada

Not known to occur in Canada.

Duration of life cycle

Annual or short-lived perennial

Seed/Fruit type

  • True seed (often shed enclosed within a single-seeded utricle and perianth)

Seed identification features

Size

  • fruit length: 1.5–2.5 mm
  • fruit width: 1.5–2.5 mm
  • seed diameter: 1.0 mm

Shape

  • fruit is heart-shaped
  • seed is round, with a notch at seed root area
  • in cross-section: both fruit and seed are a narrow oval

Surface texture

  • fruit: dull and roughened
  • seed: shiny and smooth

Colour

  • fruit: straw-yellow
  • seed: translucent, dark red

Other structures

  • perianth is attached to base of fruit, and has 5 sharp-pointed lobes
  • top of utricle extends past perianth

Similar species

Smooth joyweed (Alternanthera paronychioides)

  • not found in Canada; found in the southeastern United States
  • distribution overlaps with that of sessile joyweed
  • very similar to sessile joyweed (fruits are difficult to distinguish)
  • tends to be larger than sessile joyweed by up to 1.0 mm
  • utricle remains within perianth (utricle of sessile joyweed extends past perianth lobes)

Photos

Photo - Sessile joyweed (Alternanthera sessilis) utricle and perianth
Sessile joyweed (Alternanthera sessilis) utricle and perianth
Photo - Sessile joyweed (Alternanthera sessilis) seed
Sessile joyweed (Alternanthera sessilis) seed
Photo - Sessile joyweed (Alternanthera sessilis) utricles and seeds
Sessile joyweed (Alternanthera sessilis) utricles and seeds

Similar species

Photo - Smooth joyweed (Alternanthera paronychioides) utricles and seeds
Similar species: Smooth joyweed (Alternanthera paronychioides) utricles and seeds
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