This is Asclepias fascicularis, also known as Narrow-Leaf Milkweed, and Mexican Whorled Milkweed. This perennial milkweed attracts many different birds, bees, and butterflies. Growing to a maximum height of about 4 feet these plants must live in the full sun. The blossom color changes from pale green to white and finally to a light pink starting in the middle of the Summer and lasting until early Fall. Not only is this a larval host plant for the Monarch, Queen, and Soldier Butterflies, but it is a nectar source for many other beneficial pollinators. Asclepias in general are documented nectar sources for the Monarch, Orange-edged Roadside-Skipper, Dina Yellow, Carus Skipper, Eastern Tiger Swallowtail, and Falcate Metalmark butterflies. It is also the nectar source for the Clarks sphinx, and Milkweed Tussock moths. USDA Hardiness Zones 6 to 10.