2 questions about Daturas.

1) A couple years ago my dad and I got a purple, double-flowered Datura from a plant sale at the Denver Botanic Gardens; that summer it bloomed in a pot, produced seeds which scattered around, and died.

The following year, a few Datura plants emerged from the garden, but they were in shade and did not bloom before winter.

However, this summer new plants returned from the roots of last year's plants. It's obvious that they are the same plants because they are in the EXACT same locations, each plant now has 2 stems growing from the same base, and you can still see the dead nub of last year's stem along with a fleshy bulbous mass where the stem meets the roots.

I thought that Daturas were annuals, especially in Zone 5, and last winter we had a hard freeze of -20F. Is this perennial-like growth possible/normal in Datura?

2) In a very hot, dry location about 40 feet away, a Datura plant mysteriously appeared and grew up to have pure white flowers and resemble the jimson weed that grows wild around the southwest or re-seeds itself in gardens in very old neighborhoods. Yes, I know that jimson weed is Datura. But my question is, is it normal for cultivated Daturas to revert to their wild form after a couple generations?