Description ²

Plants prostrate annuals (may overwinter in cracks in sidewalk), ascending in shade or competition, hairy, typically not more than 15 cm tall and usually forming mats up to 20 cm. Largest internodes up to 2 mm in diameter. Stipules divided. Leaves oval to rotund, shallowly serrated. Glands and appendages usually pinkish. Fruits and ovaries with pilose hairs. Seeds with abrupt, sharp ridges along the surface, seeds white.

Habitat and Distribution ²

Like E. maculata, there have not been many reports of E. prostrata on the Llano (Turner et. al., 2003). However, it is a common weedy species in lawns and gardens in Lubbock, Lamesa, Midland and likely elsewhere. Also like E. maculata, it prefers disturbed soil with adequate moisture and is often found growing with E. maculata and E. stictospora.

Comments ²

Plants are most similar to E. stictospora on the Llano. It can be distinguished from it by the following characters:

Euphorbia prostrata: Appendages a light purplish pink with magenta gland; hair on capsules usually not dense and straight (pilose or occasionally curving or even nearly appressed); seeds ridged, not pitted.
Euphorbia stictospora: Appendages usually white with yellow or sometimes red glands; hair on capsules dense and curving (villous); seeds pitted.

When reading descriptions like the one in Manual of the Vascular Plants of Texas (Correll and Johnston, 1970), it can be difficult to distinguish E. prostrata from E. maculata without looking at the seeds or hairs. The leaves are also quite different and can provide a good character to differentiate the two, especially in combination with the other characters:

Euphorbia prostrata: Oval to rotund leaves always lacking a "splotch"; leaf bases more equal than E. maculata (still unequal); hairs on fruits generally not appressed; ridges on seeds coming to a sharp edge.
Euphorbia maculata: Oblong leaves often with a reddish or purplish “splotch” on them (not always); leaf bases more unequal than E. prostrata; hairs on fruits always appressed; ridges on seeds rounded.

Because of the abundance of these two species as lawn and garden weeds, it is usually fairly easy to find the two species to compare.

Sources and Credits

1. (c) Nathan Taylor, all rights reserved, uploaded by Nathan Taylor
2. (c) Nathan Taylor, some rights reserved (CC BY-SA)

More Info

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