Help identify roadside plant please!

I spotted this plant growing on the roadside. I stopped to take a look and tried to gently pull a piece out with roots attached but the stem pulled out very easily with no roots attached. I Googled till the cows came home & found nothing even close. I asked at a few local garden centres and no luck there either. I think it is beautiful and was thinking of digging one up and putting it in a pot or right into my garden. Do any of you have an idea of what it might be?? I can't wait to find out. Thanks.....

 

Milkweed (Asclepias)

 

Thank you Michael.

 

I planted one in my garden then spent the next year trying to stop it. It was sending up shoots 5 feet away.
I currently have it contained inside a pottery ring to depth of 16" which seems to hold the roots from spreading.
Very pretty flower but I reccomend that you restrict it.

 

Good for attracting Monarch Butterflies, though, it is the main food plant for their caterpillars

 

Also a good idea to pluck the unripe seed pods and destroy / discard them, if you don't want it to spread.

 

Planting seeds may be the best way to grow this plant. It has a long tap root, not always easy to transplant. Easy to grow from seed.