Mine was not invasive at all. My DD has 2 on a stone wall & has no problem with it being invasive. IMO it is our very best vine here in TX.

Thanks, but my question was specific. Given that it MAKES SEEDS, which I assume drop, how can it NOT be invasive? That is, if you want to propagate it everyone says to just collect seeds in the fall.

I cannot help you with that. I have never had seedlings coming up from mine. Maybe someone else will come along with the answers to your question.

Lots of plants make seeds that are easily spread or freely dispersed. That does not make them invasive. And as a native species, crossvine cannot technically be considered "invasive". Aggressively colonizing may be better terminology but even crossvine is not nearly as aggressive a spreader as is trumpet vine, also a NA native species. Spreading of either is primarily from root shoots, not seeds.

OK, but I have to press the question. If it drops seed, why doesn't it spread? That's EXACTLY what Trumpetvine does, and it spreads! So how come Trumpetvine spreads uncontrollably and Crossvine does not? Are Crossvine seeds less likely to germinate for some reason?

Now, I've already put in some Tangerine Beauty Crossvine, and everything I read about it says that it's PERFECT for my application. In fact, if it spreads, I won't mind that much. But I'm told it doesn't spread, and I don't understand why, if it drops seeds.

Neither vine spreads primarily from seed - both are inclined to spread almost exclusively by root shoots, trumpet vine far more aggressively than crossvine.

In all the many threads posted here regarding the intractable nature of trumpet vine, none have outlined self seeding as a serious drawback. Mine certainly never did!!

Nearly all plants drop seeds but do not become invasive. Gardengal is correct, what makes Trumpetvine invasive is it's persistent ability to send up new shoots from the roots.

OK, that's interesting. So in NEITHER Crossvine or Trumpetvine are the seeds particularly active, germination-wise. Many, many plants produce loads of seeds that are wind-borne or bird-borne, and those plants spread crazily by self-seeding. True, not all really become nuisance plants. All kinds of weeds do that. Now, people say that cultivating Crossvine is easy by planting harvested seeds. That doesn't seem consistent. BTW, nearly all plants do NOT drop seeds.

It may not seem consistent to say you can propagate crossvine by sowing seed and yet it doesn't spread aggressively by self seeding in nature. But it is. We propagate many plants by deliberate and careful seed sowing which don't naturally spread much that way. In the wild there are numerous barriers to seed success. And even if a plant does self sow, that doesn't make it invasive, or an aggressive spreader, which is what I think you are meaning. Normal gardening activity controls self sowing in a cultivated setting.

"BTW, nearly all plants do NOT drop seeds." I don't really understand this statement. Can you explain what you mean? All flowering plants, other than artificially produced sterile cultivars, set and drop seed. Otherwise there would be no point in their having flowers.

Weeds self sow, and are always aggressive spreaders. Many of my plants drop seeds, and I almost always get volunteers coming up. They aren't nuisance spreaders because, er, I pull them up. Not sure what deliberate and careful has to do with it. If seeds drop to the ground, manage to get buried slightly, and are watered, they'll usually grow. No deliberateness required. Deliberateness and carefulness do help if you want them to come up in specific places at specific times, though.

What folks seem to be saying is that Crossvine drops seeds, and they don't necessarily grow, but their germination appreciates deliberateness and carefulness.

Very few plants have a very high seed germination rate under natural growing conditions. That's why many plants produce so many seeds - they overproduce to ensure at least a modest percentage will germinate to carry on the line. Literature suggests that Bignonia has a germination rate of only 40-60% and the seeds remain viable for only a year.

Compare that to Buddleia davidii, with each individual flower raceme able to produce as many as 40,000 seeds and with a 80% germination rate and a 3-5 year seed viability. Now that is serious invasive potential!

"Not sure what deliberate and careful has to do with it."

Deliberate and careful has everything to do with it. It is how we humans improve the odds. We provide appropriate soil, water and protection. As GG said, if left to nature germination rates are not as high.