we would need an accurate latin name of exactly what you are trying to germinate.. to give you a precise answer ...

your own choice of words.. shows the possible confusion...

ken

There is a white datura inoxia that is also called moonflower in my mother's area. Sometimes people posting about moonflower will add vine or datura descriptor which leads me to believe that both terms are commonly used for both plants in many areas.

Other plants are called moonflower as well. I mostly use Latin names to avoid the confusion.

Have you tried nicking or scratching the coat of the vine, impomoea alba, seeds before planting? Or soaking them overnight? I have had good germination with winter sowing them but they bloom very late for me so I no longer plant them.

Check out the annual forum for more info about impomeoa alba by using the search box near the bottom of the annuals page.

A Google search turns up the botanical (Latin) name for moonflower is Ipomoea alba while the botanical name for datura is Datura stramoneum. The common names for Datura stramoneum include moonflower and jimson weed.

But is Datura and Moon Flower used interchangeably?

From what I read, it would appear the term moonflower is used for more than one genus.

I'll post picture. Have no idea of latin name but they come up every year. I didn't think they were hardy in this zone either, but I guess they reseed very easily. This is the datura, not the vining moon flower, which I think is similar to a morning glory vine.

the bees linger after dark on them

I'm so jealous!!!!! Yes, that's the moon flower vine I've been trying to grow for years. No luck this year either. I notice there are very few seeds in a packet, and the seeds are BIG. Wish they were are vigorous as my morning glories. I have to pull those out by the bucket full every summer; way too many growing everywhere!

I have seen Datura listed as "moonflower" at the local nursery.

um, Moonflower, aka calynyction aculeatum, aka ipomea alba is the vine whereas your picture shows a datura, aka brugmansia (inoxia?) - botanists, hey! - aka jimson weed and a host of other common names.

Even the Latin nomenclature lets us down sometimes

Don't even bother trying to start the moonflower seeds unless you can keep them toasty and warm. They really won't germinate unless the soil temperatures are kept higher such as with a heat mat. Also as others have said, try sanding, filing or nicking the seed coat.