Butterfly Weed Seeds. Bright, sun-loving plants are filled with brilliant orange flower clusters 10 cm (4″) across from June through to September. Mound shaped plants average 60 cm (24″) tall. Like its name suggests, this beautiful plant is a favourite of butterflies and other nectar loving insects. Butterfly Milkweed is a native Ontario perennial wildflower that is very heat and drought tolerant and an excellent choice for the low maintenance garden.