Spotted spurge (Euphorbia maculata, Euphorbiacae) is a fairly common weedy annual in much of the United States. Although native to the east it now inhabits the Pacific coast as well. It’s relatively intolerant of competition so it’s most often found in open areas like gardens, lawns, and fields.
Spotted spurge can be recognized in part by the hairy, reddish stems and small, oval leaves that usually have red spots. Each plant’s leggy stems can form a dense mat over a foot in diameter. The low, spreading growth habit can inhibit the growth of more desirable plants like perennials, turf grass, and crops.
As with plants in the milkweed/dogbane family (Apocynaceae), plants in the spurge family exude sticky white sap when damaged. Spurge sap is a skin irritant, and it can be toxic to some animals when consumed in sufficient quantities.