Tweedia caerulea Blue Milkweed Vine
Truly blue flowers are rare in the garden, turquoise blooms rarer still. Tweedia caerulea is a tropical milkweed vine that blooms clusters of star-shaped pale blue flowers with turquoise centers all summer long.
Tweedia is a perennial vine that will grow to 10 feet if trellised, or form a 2' to 3' mound without support. Native to Brazil and Uraguay, it's easy to grow in warm zones 8 - 10. It prefers sun or part shade, is fairly drought-tolerant, quite tough for something that looks so ethereal.
In cool zones, grow it as an annual. Like all milkweeds, Tweedia forms long pods loaded with silky seeds that float on the wind. New plants will appear the next rainy season.
Monarchs love this plant.