geraniums and cranesbills

genus Geranium

Member of geranium family (family Geraniaceae)
dicots (class Magnoliopsida)
flowering plants (subphylum Angiospermae)

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

Leaves are palmately lobed to divided, except for herb robert (Geranium robertianum), little-robin (Geranium purpureum), and canary island geranium (Geranium palmatum).

When counting segments, it may be easiest to count the mid-rib veins radiating from a common point. Unless specified otherwise, each segment is further palmately lobed and/or toothed in outline, although the veins are pinnate.

Except where specified otherwise, geraniums have 2 flowers per inflorescence. In many cases, one flower is open while the other one is closed.

All species may be ± glandular anywhere. This is never a distinguishing feature.

Key features:

root thickness
petal length
anther color [consider brushing off pollen to reveal]
stigma lobe color
[most that most anther/stigma colors documented here are sampled from CalPhotos and may not be accurate or reflect the full color range]
leaf shape and width (across all segments)
stem hair pattern
if fruit is present, tip and base shapes can be diagnostic

notched petal tips

cut-leaved crane’s-bill
Geranium dissectum

stem hairs hairs rough, spreading to reflexed
leaf blade 2.5–5.4 cm wide, divided 75–95% to base
5–7 leaf segments, diamond-shaped
petals 2.9–5.8 mm, ± notched, rose-purple
anthers dark or pale purple
stigma lobes red-purple

northern cranesbill
Geranium bicknellii

stem hairs short, stiff
leaf blade 2–7 cm wide, divided 85–95% to base
5(7) segments, wedge-shaped
petals 4–6 mm, ± notched, very pale purple with dark purple veins
anthers pink and/or purple
stigma lobes salmon or beige

carolina crane’s-bill
Geranium carolinianum

stem hairs dense, short, spreading or reflexed
leaf blade 2.5–8.5 cm wide, divided 70–90% to base
5(7) segments, oblong to wedge-shaped
petals 5.5–6 mm, ± notched, white to rose-pink
anthers dark purple
stigma lobes red-purple

small-flowered crane’s-bill
Geranium pusillum

stem hairs soft
leaf blade 1.5–4.8 cm wide, divided 30–75% to base
7 leaf segments, wedge-shaped
petals 2–3 mm, ± notched, pink to violet
5 fertile stamens (outer 5 stamens lacking anthers) [all others have 10 fertile stamens with anthers]
anthers dark purple
stigma lobes beige

dove’s-foot crane’s-bill
Geranium molle

stem hairs ± sparse, soft
leaf blade 0.9–5.2 cm wide, divided 50–75% to base
7–9 leaf segments, obtriangular
petals 3–10.5 mm, notched, red-purple [usually pale purple with purple veins]
anthers dark purple
stigma lobes red-purple

solander’s geranium
Geranium solanderi

stem hairs spreading to reflexed, not appressed, non-glandular
leaf blade 1.4–5.7 cm wide, divided 45–85% to base
5–7 leaf segments, obtriangular
petals 3–8.1 mm, rounded, ± purple
pedicel 8–34 mm, hairs spreading or reflexed, not appressed, 0.2–2 mm
anthers cream colored
stigma lobes cream colored

petal tips barely notched

alderney crane’s-bill
Geranium core-core

stem hairs sparse, stiff, reflexed, appressed
leaf blade 1.5–5.6 cm wide, divided 55–80% to base
5–7 leaf segments, broadly wedge-shaped
petals 3.1–7.1 mm, rounded or ± notched, purple
pedicel 11–31 mm, hairs reflexed, appressed, 0.2–0.6 mm
anthers cream colored
stigma lobes cream colored

new zealand geranium
Geranium retrorsum

appears in CalFlora, but not described by Jepson
likely to be misidentified alderney crane’s-bill (Geranium core-core) (source1, source2)
SF Presidio, Twin Peaks, and urban Berkeley