The Butterfly Plant Hello Yellow, 'Asclepia tuberosa Hello Yellow, has all the advantages of the native wildflower but with the added appeal of shockingly bright yellow flowers. Butterflies love to visit this flower for nectar and the foliage of Asclepias is the only thing Monarch butterfly caterpillars will eat. Asclepias is tolerant of both wet and dry soils and needs plenty of sunshine to bloom heavily. This plant is hardy zone 4-9.