We have Cardinal Climber here every year and I have only had to plant the seeds once or twice in 15 years since they reseed so abundantly. So, I consider them to be somewhat invasive, but it just depends on where they are growing and what else is around them. I just yank out the seedlings while they are still small if they are someplace where I really don't want them, but otherwise leave them alone. The hummingbirds love the flowers and I like that the foliage is unique.

Often, the volunteers sprout very early in the season and get killed back by late freezes or frosts, so that helps keep them from overpopulating and driving me nuts.

They do continue to sprout sporadically over the summer, and often I won't even notice they sprouted and grew someplace...like in the midst of other vining plants or climbing tomato cages or cornstalks or something....until they start to bloom.

If the cardinal vine you are talking about is cardinal creeper instead of cardinal climber, I haven't grown that one.

Dawn

Thanks. I want to grow the cardinal vine. Didn't know there was a cardinal creeper! Want it to draw humming birds.
Is it to late to start one from seed this yr?

Here is a description of the two cardinal vines
Tells how to start them, but not when it's too late!
I believe I have the Cyress Vine and the red morning glory.
The hybrid of those two is what this author calls the Cardinal Climber. At any rate, she shows a close-up of the leaves so maybe you can tell which one you have, or want!
They do great down here in Georgia, but are just now coming up in my garden and then it will take quite a while for them to bloom. So maybe you could still start them in Oklahoma.

I just looked further and found references to Cardinal Creeper as Ipomoea horsfalliae--it is very tropical with much larger leaves and flowers.

Good luck!

Here is a link that might be useful: Cardinal climber and its cousins

Cardinal climber seeds that have reseeded naturally in my garden sprout all summer long, generally after a good rainstorm, so I don't think it ever is too late to plant it. It grows quickly and flowers fairly quickly after sprouting. We still have 5 to 6 months of warm weather/growing season left and, often, my cardinal climber vine blooms until almost Thanksgiving, or the first frost, whichever comes first. It generally is still in bloom long after the hummingbirds have begun their journey south for the winter.