Snow on the mountain (Euphorbia marginata, Euphorbiaceae) is an interesting and attractive annual that is native to the Great Plains. Here it is most often encountered on dry slopes, near prairie dog towns, and in other open areas where competing vegetation is relatively sparse. Over the last two centuries it has been spread throughout much of North America by people, and today it can also be found in disturbed areas along roads, fields, and empty lots.
While the plain green lower leaves and tiny yellow flowers are unremarkable, the upper leaves and bracts of this plant are really what make it eye-catching. These leaves are variegated with white and green, creating a contrast that may help attract pollinating insects to the otherwise uninteresting flowers. The stems produce a sticky white sap that can cause contact dermatitis, and it is generally considered toxic to people and livestock.