Interchangeable plants, and at least one is deadly

Q: What is the difference between Brugmansia and Datura?

A: Not much, hence all the confusion. The taxonomy of these plants seems to confuse even the experts.

Both are called angel's trumpets, and both are bold, tropical-looking plants with fragrant bell-like flowers in summer. Some references, such as "Sunset Western Garden Book," use the names interchangeably. When you buy them in the nursery, you can never be sure whether you're getting a Datura or a Brugmansia.

The distinguishing difference between the two is that the flowers of Brugmansia droop, while Datura's flowers point up or are held out at a right angle to the stems.

In their warm, native habitat of South America, the differences would be clearer. There Brugmansias grow into large woody shrubs, while Daturas are annuals. The fruit of Brugmansia are smooth, elongated pods, while those of Datura are round and spiny.

Here in our colder climate, where both plants are grown as annuals (although they can be overwintered indoors), they grow to about the same height. All parts of the Datura are extremely poisonous. Because of such name confusion, and the names being used interchangeably, I'm unable to figure out whether Brugmansia is equally deadly.

Q: We have a question none of the master gardeners has been able to answer. Why did the purple asters we planted bloom white the following year? Ever heard of that happening? We live in Kirkland.

A: Plants do lots of weird things, but I've never heard of that one. Grafted shrubs can revert back to an earlier color or form, but that isn't the case with perennials such as asters. All I can guess is that a) you've mixed up where you planted which aster, which happens to me quite often with one plant or another, or b) there was a bit of root of a white aster in the pot, and the purple one died out and the white one prospered. It seems a bit far-fetched, but possible. If any readers have other explanations for this garden mystery, I'd love to hear them.

Q: Can you please tell me the most fragrant varieties of sasanqua camellia, and possibly good sources for them in the Portland area?

A: Sasanqua camellias are widely available in nurseries in the autumn and winter when they flower. It's a good idea to select sasanquas when in bloom, because there are so many flower colors, sizes, shapes and plant habits to choose from. I suggest you call around to area nurseries starting in November to find out what's available where. Larger nurseries will probably order plants for you if you know which ones you'd like.

Many of the sasanqua camellias are fragrant, including frilly white 'Setsugekka,' 'Apple Blossom,' 'Paradise Venessa' and 'Narumigata.' Doing a sniff test for flower perfume is another good reason to buy these plants in bloom, keeping in mind that they'll be more fragrant on warmer days than on cold ones.

Q: I love the bright colors and shimmery flowers of the so-called "mini petunias," but I have a hard time cultivating them. They just don't grow well, and sometimes just up and die. Occasionally the leaves will turn dark purple but there's no growth and very few flowers. They are container-grown in full sun with regular water. Any ideas?

A: Calibrachoa, or million bells, are fairly new annuals that look like little petunias and come in a wide range of colors. Since these plants rarely have disease or insect problems, my guess is that the problem is over-watering, not providing good soil, or planting them out so early in the season that they get set back by cold.

Calibrachoa can take some drought, so let the soil dry out between waterings. Make sure you're using fresh, good-quality potting soil in all your containers, for potted plants are dependent on this medium to provide their nutrients.

Even though nursery tables are full of annuals by late April, in a cold spring like this one it's best to wait well into May before putting annuals outdoors. When heat-loving plants such as million bells or coleus look as if they're melting away, it's usually because they dislike the cold nights. Plants can be so set back from early chill that they never fully recover.

Valerie Easton also writes about Plant Life in Sunday's Pacific Northwest Magazine. Write to her at P.O. Box 70, Seattle, WA 98111 or e-mail planttalk@seattletimes.com with your questions. Sorry, no personal replies.