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• Acanthospermum australe

Acanthospermum australe — Paraguay starburr

Facts

Paraguay starburr is native to South America and introduced in many other parts of the world. It only occurs occasionally in Massachusetts. It can be recognized by its prostrate habit, opposite leaves and five-parted, vaguely star-shaped fruit that adheres to clothing and fur with hooked barbs.

Habitat

Anthropogenic (man-made or disturbed habitats)

Characteristics

• Flowers

  Bases of bract appendages

  NA

  Bract cycle number

  there are two main cycles of bracts

  Bract shape

  • the main bracts are elliptic (widest near the middle and tapered towards the base and tip)
  • the main bracts are lanceolate (widest above the base, then taper narrowly towards the tip)

  Bract spines

  the bracts are prickly on the outer side

  Bract texture

  • the bracts appear leathery or hardened
  • the bracts have a similar texture to a leaf

  Bracts

  there are at least two distinct forms of bracts in different cycles

  Disk flower color

  yellow

  Disk flower lobe number

  5

  Disk flower number

  • 1-5
  • 11-20
  • 6-10

  Disk flower reproductive parts

  the disk flower has either only pollen- or only seed-producing parts

  Disk flower shape

  the disk flower is tube-shaped (cylindrical), or gradually widening like a funnel

  Flower head number

  each flowering stem has only one to three flower heads on it

  Flower head outer flowers

  at the outer edge of the flower head, each flower has a single enlarged lobe or strap

  Flower head platform

  the base has papery scales on it

  Flower head platform surface

  NA

  Flower head position

  each of the flower heads is separate on its own peduncle (stalk), not clustered in groups

  Flower head profile

  the disk is flat or nearly flat across the top

  Flower head shape

  the flower head is hemispherical (like the bottom half of a sphere)

  Flower head width

  4–6 mm

  Flower type in flower heads

  the flower head has tubular disk flowers in the center and ray flowers, these often strap-shaped, around the periphery

  Inflorescence branching (Solidago)

  NA

  Inflorescence shape

  • NA
  • the flower heads grow in clusters from the axils of the branches or leaves

  Inflorescence stem

  hairs are present on the stem of the inflorescence

  Number of bracts at flower head base

  9–16

  Ovary beak

  there is no beak on the ovary

  Ovary cross-section

  the ovary is compressed (flattened)

  Ovary hair type

  the ovary has no hairs on it

  Ovary hairs

  the ovary has no hairs on it

  Ovary lines or ribs

  there are four to six lines or ribs visible on the ovary

  Ovary profile

  in profile, the ovary is roughly elliptical (widest in the middle, tapering to both ends)

  Ovary surface

  the ovary surface is textured with tiny points, bumps or wrinkles

  Ray flower color

  • orange
  • yellow

  Ray flower reproductive parts

  the ray flowers have carpels or stamens, but not both

  Ray flowers

  • 1-5
  • 6-10

  Ray length

  Up to 2 mm

  Reproductive system

  all the flowers on the plant contain both carpels and stamens

  Rim at top of ovary

  the central flowers have no disk-shaped platform above the ovary

  Scale tip

  NA

  Style branch number

  the style has one branch

  Width of flower head base

  3–5 mm

• Fruits or seeds

  Dispersal unit

  the seeds fall off or are dispersed separately from one another

  Number of pappus parts

  0

  Ovary beak length

  0 mm

  Ovary length in developed fruit

  7–9 mm

  Ovary width in developed fruit

  3–5 mm

  Seed hair tuft bases

  NA

  Seed hair tuft color

  NA

  Seed hair tuft details

  NA

  Seed hair tuft length

  0 mm

  Seed hair tuft tips

  NA

  Seed hairs uniform

  NA

  Seed tuft scale number

  0

  Seed tuft type

  there is no pappus on the ovary

  Top of disk flower ovary

  NA

  Tuft or plume on fruit

  NA

• Glands or sap

  Leaf blade glands

  the leaf blades have glandular (translucent) dots or scales

  Ovary glands

  there are glands on the ovary surface

  Sap

  the sap is clear and watery

• Growth form

  Growth form

  the plant has one or more free-standing stems

  Horizontal rooting stem

  there are no stolons

  Plant lifespan

  the plant is annual, it lacks evidence of previous years' growth

  Spines on plant

  the plant has no spines

  Underground organs

  • there are only slender roots on the plant
  • there is a thickened taproot on the plant

• Leaves

  Final leaf segment length (compound lvs only)

  0 mm

  Final leaf segment width (compound lvs only)

  0 mm

  Hairs on underside of leaf blade

  the underside of the leaf is not hairy, or has very few hairs

  Hairs on upper side of leaf blade

  the upper side of the leaf is not hairy, or has very few hairs

  Leaf arrangement

  opposite: there are two leaves per node along the stem

  Leaf blade base

  the leaf has a distinct petiole

  Leaf blade base shape

  the base of the leaf blade is cuneate (wedge-shaped, tapers to the base with relatively straight, converging edges), or narrow

  Leaf blade edges

  • the edge of the leaf blade has no teeth or lobes
  • the edge of the leaf blade has teeth

  Leaf blade flatness

  the leaf is flat (planar) at the edges

  Leaf blade hairs

  the leaf blade has hairs with glands at their tips

  Leaf blade length

  13–37 mm

  Leaf blade shape

  • the leaf blade is ovate (widest below the middle and broadly tapering at both ends)
  • the leaf blade is triangular, with the stalk or attachment point on one of the sides

  Leaf blade tip

  the tip of the leaf blade is acute (sharply pointed)

  Leaf blade veins

  the leaf blade has one main vein running from the base towards the tip

  Leaf blade width

  7–32 mm

  Leaf disposition

  the leaves are nearly similar in size, prominence of teeth, and length of stalks throughout the stem

  Leaf spines

  there are no spines on the leaf edges

  Leaf stalk

  the leaves have leaf stalks

  Leaf stalk length

  3–15 mm

  Leaf tip extension

  NA

  Leaf type

  leaves are simple (i.e., lobed or unlobed but not separated into leaflets)

  Leaflet number

  0

  Specific leaf type

  the leaves are simple (i.e., lobed or unlobed but not separated into leaflets

• Place

  Habitat

  terrestrial

  New England state

  Massachusetts

  Specific habitat

  man-made or disturbed habitats

• Scent

  Plant odor

  the plant does not have much of an odor

• Stem, shoot, branch

  Leaves on stem

  there is at least one full leaf above the base of the flowering stem

  Stem internode hair direction

  the hairs are pressed flat against the plant, pointing either towards the plant's tip or towards it's base

  Stem internode hair type

  at least some of the hairs on the stem have glands

  Stem internode hairs

  the stem has no hairs between the nodes

Wetland status

Not classified

New England distribution and conservation status

From the dichotomous key of Flora Novae Angliae