Sometimes called Tropical Milkweed, Asclepias curassavica - is a good garden plant that will attract Monarch females, who use it as a larval host. These yellow flowers are of the 'Silky Gold' variety, from my garden in Long Beach, CA.

A Monarch on Asclepias curassavica - at El Dorado Park in Long Beach, CA. This park had many patches of milkweed and a good number of resident Monarchs until recent years. When the employee responsible for the butterfly-friendly plantings in the park was no longer working there, nearly all the plants were pulled out.