knotweeds, smartweeds, and waterpeppers

genus Persicaria

Member of knotweed family (family Polygonaceae)
dicots (class Magnoliopsida)
flowering plants (subphylum Angiospermae)

Except for extremely rare examples that I don't expect to encounter, there are no other wild species of this genus in the bay area.

See also knotweeds (genus Polygonum).

pink knotweed
Persicaria capitata

inflorescence ± head-like

all others are spike- or panicle-like

petioles generally winged with ear-like lobes at the base

in photos this looks more like narrow lobes that stick out or clasp the stem, and the petiole is too short to display separate wings
all below have no petioles or ear-like lobes

dotted smartweed
Persicaria punctata

dotted smartweed
Persicaria punctata

inflorescence not dense
perianth gland-dotted

visible as tiny pits in the calyx?
all below are not gland-dotted

water smartweed
Persicaria amphibia

dense spike hides individual calyxes
flower pink to red purple
found in water

spotted lady’s thumb
Persicaria maculosa

spotted lady’s thumb
Persicaria maculosa

dense spike hides individual calyxes
flower pink to red purple
no peduncle glands

pale smartweed
Persicaria lapathifolia

dense spike mostly hides individual calyxes
flower white to pink to red purple
±stalked peduncle glands

2 observed taxons / 3 unobserved taxons / 1 key

Chris’s observations: none

Taxon info: iNaturalist – Calflora – Jepson eFlora – FNA

Bay Area species: iNaturalist – Calflora