# Quotient of variety by additive group separated?

I have some sub variety of a complex flag variety and I want to take the quotient by a free action of $\mathbb{C}$. I know that this quotient exists locally as a variety. My question is whether there are general results or criteria, which guarantee, that if I patch the local quotients together the result is again separated. I know that this is true for reductive groups.

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