Euphorbia hyssopifolia, known by the common name of hyssopleaf sandmat in English and hierba de pollo ("chicken grass") in Spanish, is a member of the spurge family, Euphorbiaceae. It is an annual herb, native to Central and South America and the Southeastern United States. It has also been introduced to west Tropical Africa, India, and Australia.
Arching annual to 80 cm with leaf-bases oblique. Flowers and fruits in small loose clusters. Because it is rather confusable with the usually slightly hairier E. nutans, fruit capsules should always be opened for seeds. The seeds are cross-ridged and rather square-edged in comparison to the more irregular rounder-edged seeds of E. nutans.
Seeds: "brown to grayish white, ovoid, slightly 4-angled in cross section, abaxial faces convex, adaxial faces slightly concave to slightly convex, 1–1.4 × 0.7–1.1 mm, with 2–3 prominent transverse ridges that do not interrupt adaxial keel, or coarsely and inconspicuously pitted-reticulate." FNA (see also FNA nutans)