I saw this photo taken in Hawaii of a Mexican Butterfly 'weed", http://patrick-mcnally.aminus3.com/image/2012-10-29.html. I wondered if it is just called a weed, or if it will really spread like a weed and make me regret adding it to my landscaping. I like the appearance of the flower and it seems to be butterfly friendly from what I've read, which I'd like for that reason alone. From the description, it sounds like it grows wild so might not need a lot of special attention. Any ideas if this is ever used successfully in home landscaping?
Asclepias plants are host for Monarch butterfly caterpillars. When blooming, they are nectar plants for about any critter that partakes in such. Some Asclepias are native but this one is not, although the monarchs don't care which it is. Do monarchs get to HI? If you are just interested in nectar plants, this heavy seeding exotic is probably not the best choice.
It is not a "weed" at all. Not an aggressive spreader.
It is often used in formal gardens (and in naturalizations) and it will reproduce from seed if the ground is not disturbed at all (but in a garden situation I have never seen it spread beyond the original planting, likely any seedlings don't have a chance with regular garden maintenance.) They have a taproot so are tricky to transplant successfully. Starting from seed is how to reproduce. It does grow wild and it is very drought tolerant (because of the taproot) so it requires little, if any, maintenance. I would recommend it for a garden if you like the colour and it is a great butterfly attractor.
I grew this plant and it did well in wet soil and bloomed and got eaten up by caterpillars, all before the first frost! However, where you are it could become invasive as it readily spread by seed for me.