Delaware Wildflowers • Guides

Bidens — Tick-seed, Beggar-tick, Spanish-needle
Instead of a pappus of fine hairs to carry seeds on the wind, these have seeds with hooked barbs that stick to fur or clothing. Another characteristic of Bidens is the circle of leafy bracts (outer phyllaries) around the flower head. 13 species in Delaware, most are native.

Five have undivided leaves (some may have small lobes at the base):

Two have undivided leaves without stalks:

Bidens laevis, Smooth Tick-seed
Petals (ray flowers) over 1/2" long. Coastal plain only.

Bidens cernua, Nodding Tick-seed
Petals not more than 1/2" long.

Three have undivided leaves (sometimes lobed) with stalks 1/2" or more long:

Bidens comosa, Three-lobe Tick-seed
No petals (or very small.) Usually in dry areas.

Bidens connata, Purple-stem Tick-seed
Very similar to B. tripartita; status uncertain in Delaware, but thought to be only on the coastal plain. To ID see

Bidens bidentoides, Estuary Tick-seed
No petals; usually in shallow water. Rare.

Also see Bidens mitis below.

Eight have leaves divided into three or more leaflets:

Four have divided leaves and no, or very small, petals (ray flowers):

Bidens bipinnata, Spanish Needles
Leaves divided more than once, into many leaflets.

Bidens vulgata, Tall Tick-seed
"Outer phyllaries 10-20, with stiff-hairy margins; awns 3 - 9.5mm long."

Bidens frondosa, Devil's Tick-seed
3-5 leaflets; "Outer phyllaries 5-10, margins ciliate"

Bidens discoidea, Swamp Tick-seed
No petals; "Outer phyllaries 2-5, margins without cilia". Coastal plain only.

Four have divided leaves and petals 1/2 - 1" long:

Bidens trichosperma, Northern Tick-seed Sunflower (Bidens coronata)
"Achenes not wing-margined ... Inner achenes 4.5-9mm long ..." Coastal plain tidal marshes.

Bidens mitis, Small-fruited Tick-seed
"Achenes not wing-margined ... Inner achenes 2.5-4.5mm long ..." Leaves stalked, sometimes undivided. Rare plant of coastal plain tidal marshes.

"Achenes wing-margined ... Outer phyllaries 8-12 ... tips blunt or simply acute." Coastal plain only; adventive.

Bidens polylepis, Tick-seed Sunflower
"Achenes wing-margined ... Outer phyllaries 10-20(25) ... tips long tapering ..." Petals slightly orange at the base. Invasive adventive.

Sources: The Flora of Delaware, Herbaceous Plants of Maryland.

Copyright David G. Smith

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