There is much confusion in the gardening community over Brugmansia spp. and Datura spp., since they both were classified as Datura until 1973. The truth is, the two plants couldn't be more different. From the way they look to the way they grow to the size and colors of their flowers, brugmansia and datura are nowhere near the same plant. Think of it like having a first cousin who is tall with red hair and green eyes, while you are short with black hair and brown eyes. Learning the differences can make growing these beauties much easier.
Common Names and Growth Habits
Both have spectacularly beautiful trumpet shaped flowers, and both are sometimes called "angel trumpets," which is a misnomer. Brugmansia's much larger flowers are pendulous and point downward, as if from heaven, thus the common name angel trumpets or angel's trumpet. Datura has smaller flowers that point upward, as if from Haedes, thus the common name of devil trumpets or devil's trumpet. The main difference is brugmansia grow tall with woody bark, whereas datura are herbaceous and stay shrubby or sprawl.
Flower Sizes and Colors
Brugmansia flowers are much larger than datura flowers, in colors of white, yellow, orange, or red. Datura flowers are white, yellow, purple/white or lavender. The holy grail of breeding is to create a purple brug, but the two species are genetically incompatible, so no success yet.
Culture and Environment
The most important cultural difference is that brugmansia need shade and daturas love full sun. Some brugs can stand early morning sun, but need to be shaded from 11 a.m. on.
Brugmansia are water hogs. They need to be kept moist when grown in containers and watered daily during warm weather planted in the ground. They also need an abundance of fertilizer. Most brug fanciers fertilize at least twice a week with a 20-20-20 liquid fertilizer. The one thing you should never do is to use a bloom fertilizer on an angel's trumpet, as too much phosphorous causes severe leaf drop. Never fear, they will recover once the fertilizer is leached from the soil.
Datura are basically weeds, in fact, Jimson weed is a wild member of the datura family. They need to be kept dry, and rot easily with too much water. They also enjoy poor soils, whereas brugmansias like rich, organic soils. Daturas are pretty much carefree once they are established, while brugmansias are not.
Datura are considered annuals in all but tropical areas, so be sure to save seeds for next year's crop. Brugmansia are perennials in temperate climates, but in frigid climates must be brought indoors or into a greenhouse in the winter. In zones with less severe winter freezes, brugs can be cut back to about 3 inches tall, mulched heavily, and will come back from the roots in the spring.
Seeds and Propagation
Brugmansia roots easily from cuttings, with some species and varieties being easier to root than others. Most gardeners start cuttings in water until they get "nubbies," the little white bumps on the stem, then put them into soil. Datura are not so easy to root from cuttings, being more herbaceous, and cuttings tend to rot. The best way I've found to root datura is to find a piece that is becoming woody on the bottom and use that. They don't root well in water.
Both plants can be grown from seed, but there are huge differences. Brugmansia is only pollinated by certain insects, and seed pods are few and far between. Plus, they do not come true from seed, with most seedlings reverting back to a white bloom. The seed pods are usually long, pendulous and green, and should be picked just as they start to split. Breeders hand-pollinate their plants, which is a pretty involved process. Not all brugmansia species are cross-compatible.
One thing I love about datura is that they produce abundant seeds, although some have prickly seed pods with long thorns. The seeds can range from a light brown to black. You harvest the seeds once the seed pod starts to split, but don't wait too long, because I can tell you from experience that they will spread like wildfire if left to their own devices. Fresh seeds usually germinate readily, but older seeds may take some coaxing. There is something about compost that seems to spur older seeds to germinate. Many a gardener has tossed old soil with daturas that never came up into the compost pile, only to find them sprouting, so if you have compost handy, mix some of that with your potting mix to start your datura seeds.
Datura and Brugmansia can be found in most garden centers, even in the big box stores during bloom season. To get the prettier, named varieties, I've found several sellers online with reasonable prices. Beware, though. Check them out carefully, though, so you don't end up with something you didn't order.
Personal Knowledge and Experience