I grow annual vincas and I really love them. At first they need some water but after that they do very nicely on their own. My favorite is to mix these with gomphrenas because I like the contrast in height and shape of flowers. Plus you can cut gomphrena for the vase!

Isn't Vinca typically invasive?

Are you thinking of perennial vinca, a vine that spreads rapidly and has blue flowers, or the multi-colored, sun loving annuals?

Perennial vinca can be extremely invasive. We have been fighting a mostly losing battle for years against vinca which originates in our neighbors back yard. The only thing I have seen stop it's progress is full sun.

Annual vinca (usually available in box stores in the latter part of April) is a great annual. It is actually not a "true" vinca, but the flower is very similar, hence the name.

Perennial vinca (vinca major, vinca minor) is a real thug except in extremely dry conditions.

Ok, so the annual is typically referred to as "Periwinkle", rather than "Vinca"? This is where my confusion is coming in.

I have had experience with trying to help eradicate Vinca major and minor. It was a multi-year battle in all cases. That stuff is just as bad to get rid of (worse, in some cases) as boston/english/etc. ivy. Not fun stuff.