OregonFlora: Euphorbia helioscopia vs. Euphorbia crenulata

	Euphorbia helioscopia	Euphorbia crenulata
	mad woman's milk, wartweed	western wood spurge
Habit	Herbs annual, 1–5 dm; stems,erect, glabrous to sparsely hairy.	Herbs or subshrubs annual or biennial, 1.5–5 dm; stems erect, glabrous.
Leaves	alternate (upper leaves may be opposite), obovate to spatulate, 10–30 × 5–15 mm; margins toothed in at least upper 25%; entire below; tips rounded; surfaces glabrous, sessile.	elliptic to spatulate, 10–35 mm × 4–12 mm; margins entire to slightly crenate; tips obtuse to acuminate; surfaces glabrous; lower leaves alternate, sessile or with minute petioles; upper and floral leaves opposite or whorled, sessile.
Inflorescences	involucres cone-shaped, 1–1.5 mm; glands not horned.	involucres bell-shaped, 2–3 mm; glands 2-horned.
Flowers	styles divided less than halfway to base.
Fruits	round, 2.5–3 mm.	oblong, 3–3.5 mm.
Seeds	ovoid, 1.5–2.5 mm, with reticulate pitting.	round to oblong, 1.5–2.5 mm, with reticulate pitting.

	Euphorbia helioscopia	Euphorbia crenulata
Distribution	[WildflowerSearch map] [BONAP county map]	[WildflowerSearch map] [BONAP county map]
Discussion	Disturbed areas. Flowering Apr–Jul. 0–200 m. CR, WV. CA, WA; scattered throughout North America; Asia, Europe. Exotic. Euphorbia helioscopia is easily confused with E. spathulata. The former is an exotic species introduced from Eurasia, while E. spathulata is considered native. The most reliable characteristic separating these taxa is the size of the involucres.	Dry areas. Flowering Apr–Jul. 0–1600 m. Casc, CR, ECas, Est, Sisk, WV. CA, NV; AZ, CO. Native. Euphorbia crenulata greatly resembles the European native E. peplus. They differ only in seed pitting characteristics and lower leaf petioles. Their genetic affinity is worthy of study.
Source	Flora of Oregon, volume 2, page 645 Stephen Meyers	Flora of Oregon, volume 2, page 645 Stephen Meyers
Sibling taxa	E. crenulata, E. cyparissias, E. dentata, E. esula, E. lathyris, E. myrsinites, E. oblongata, E. peplus, E. spathulata	E. cyparissias, E. dentata, E. esula, E. helioscopia, E. lathyris, E. myrsinites, E. oblongata, E. peplus, E. spathulata
Web links	Local floras: BC, CA, OR, WA Local Web sites: CalFlora, CalPhotos, Flora NW, PNW Herbaria WildflowerSearch iNaturalist (observations) USDA Plants Database LBJ Wildflower Center SEINet Plants of the World Online Encyclopedia of Life Wikipedia Google Image Search	Local floras: CA, OR Local Web sites: CalFlora, CalPhotos, Flora NW, PNW Herbaria, Turner Photog. WildflowerSearch iNaturalist (observations) USDA Plants Database LBJ Wildflower Center SEINet Plants of the World Online Encyclopedia of Life Wikipedia Google Image Search

Euphorbia crenulata

mad woman's milk, wartweed

western wood spurge

Habit

Herbs annual, 1–5 dm; stems,erect, glabrous to sparsely hairy.

Herbs or subshrubs annual or biennial, 1.5–5 dm; stems erect, glabrous.

Leaves

alternate (upper leaves may be opposite), obovate to spatulate, 10–30 × 5–15 mm;

margins toothed in at least upper 25%; entire below;

tips rounded;

surfaces glabrous, sessile.

elliptic to spatulate, 10–35 mm × 4–12 mm;

margins entire to slightly crenate;

tips obtuse to acuminate;

surfaces glabrous; lower leaves alternate, sessile or with minute petioles; upper and floral leaves opposite or whorled, sessile.

Inflorescences

involucres cone-shaped, 1–1.5 mm;

glands not horned.

involucres bell-shaped, 2–3 mm;

glands 2-horned.

Flowers

styles divided less than halfway to base.

Fruits

round, 2.5–3 mm.

oblong, 3–3.5 mm.

Seeds

ovoid, 1.5–2.5 mm, with reticulate pitting.

round to oblong, 1.5–2.5 mm, with reticulate pitting.

Euphorbia crenulata

Distribution

[WildflowerSearch map]

[BONAP county map]

[WildflowerSearch map]

[BONAP county map]

Discussion

Disturbed areas. Flowering Apr–Jul. 0–200 m. CR, WV. CA, WA; scattered throughout North America; Asia, Europe. Exotic.

Euphorbia helioscopia is easily confused with E. spathulata. The former is an exotic species introduced from Eurasia, while E. spathulata is considered native. The most reliable characteristic separating these taxa is the size of the involucres.

Dry areas. Flowering Apr–Jul. 0–1600 m. Casc, CR, ECas, Est, Sisk, WV. CA, NV; AZ, CO. Native.

Euphorbia crenulata greatly resembles the European native E. peplus. They differ only in seed pitting characteristics and lower leaf petioles. Their genetic affinity is worthy of study.

Source

Flora of Oregon, volume 2, page 645
Stephen Meyers

Sibling taxa