Nodding Spurge

Euphorbia nutans

Description 6

Plants robust, ascending to erect annuals; may attain a height of over 30 cm tall; not typically branching much at the base. Stems hairy, often only on a line on the upper sides, largest internodes may get up to 3 mm in diameter. Stipules divided or fused on both sides of the stem except near the apex where they separate; usually serrated. Leaves usually oblong-lanceolate and slightly crescent shaped; leaves may have a red “splotch” in the center along the midvein; most leaves 1.5-2 cm long and longer. Cyathia about 1 mm across. Appendages mostly entire. Styles long and slender. Fruits glabrous. Seeds wrinkled (transverse and more than 3); to nearly black in color.

Comments 6

Euphorbia hyssopifolia and E. hypericifolia most closely resemble E. nutans in Texas. The three are frequently confused but can be distinguished using the following characters:

Euphorbia nutans: Stems always with some short crinkled hairs (in Texas; may be glabrous elsewhere; see note on hairs below); stipules shorter than 1 mm erect; cyathia solitary, at most in dense leafy inflorescences.
Euphorbia hyssopifolia: Stems glabrous or with pilose hairs; stipules shorter than 1 mm erect; cyathia solitary, at most in dense leafy inflorescences.
Euphorbia hypericifolia: Stems always glabrous; stipules longer than 1 mm spreading away from the stem; cyathia in dense leafless inflorescences (a single solitary cyathium is usually present at the node before the nodes holding the dense inflorescences).

During the 1930's and 1940's, Louis Cutter Wheeler (the Euphorbia expert of the time) called this species E. maculata based on some misunderstanding of the type specimen. This has long since been resolved with the name E. nutans representing the larger plant and E. maculata representing the smaller plant (photos can be found here). Occasional specimens representing this outdated taxonomy can be found. For more information concerning this, please read The application of the Linnaean names of some New World species of Euphorbia subgenus Chamaesyce by Daniel Burch (1966, Rhodora 68:155–166; also available on JSTOR).

Note on the hairs 6

Euphorbia nutans usually has hairs on the upper stems and if they don't they will have them at the very base of the main stem. Hairs may grow throughout the stem, but they typically fall off in the middle, and often at the base. Very occasionally, there are none at the apical stems, but some at the bases of the stems. I have never seen a plant without hairs north of central Mexico. Also, the hairs at the base of the stems may be different in that they are short, straight and completely encircling the stem. The apical hairs are typically on only one side of the stems.

In more tropical regions, such as central Mexico, the hair characteristic breaks down altogether and plants become glabrous. From a worldwide perspective, E. hyssopifolia and E. nutans can only be distinguished by seeds but there are populationl trends and geographic limits that can be helpful outside the United States.

Photography suggestions 6

To get a good ID, I recommend the following:

1. A habit shot (which will narrow it down to E. nutans and E. hyssopifolia most of the time)
2. A close up of the UPPER sides of apical stems
3. A close up of the very base of the plant including basal branches

An observation with these three photos should be identifiable except under the most stressful circumstances (for the plant). Ultimately, the plants are most easily identified by their seeds, which can be extracted by a process described here.

Sources and Credits

  1. (c) Sam Kieschnick, some rights reserved (CC BY-NC), http://www.inaturalist.org/photos/2062883
  2. (c) Sam Kieschnick, some rights reserved (CC BY-NC), http://www.inaturalist.org/photos/2062884
  3. (c) Chuck Sexton, some rights reserved (CC BY-NC), https://www.inaturalist.org/photos/7332178
  4. (c) Nathan Taylor, some rights reserved (CC BY-NC), http://www.inaturalist.org/photos/5326193
  5. (c) dale_denham_logsdon, some rights reserved (CC BY-NC), http://conabio.inaturalist.org/photos/4031289
  6. (c) Nathan Taylor, some rights reserved (CC BY-SA)

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