As the seeds of leafy spurge (Euphorbia esula L.) increase in age after fertilization, their color changes from yellow to yellow with brown tips, to brown ends with a narrow yellow band, to brown with an orange band, and to a reddish-brown seed, followed in order by brown, gray-brown, gray, and finally, mottled. The last four are viable; the others are not. Mowing of leafy spurge to prevent viable seed production must be done before seeds have turned brown. Brown seeds appeared 10 to 13 days after fertilization depending upon seasonal conditions.