As the winter daylight begins to lengthen, and those deciduous trees with the big purplish and white flowers begin to bloom here in Napa, an old question has arisen once again.

I'll paraphrase it: "How can tulip trees be magnolias? I thought magnolias were evergreen and had fragrant, big white flowers in the summer."

The confusion shows that the world of plant names can seem like a tangled can of worms. And when you start to study it, it seems to get worse!

First off, most people know that tulips don't grow on trees. That bulbous perennial herb from the lily family, originating in Central Asia, supposedly got its name from the Turkish word "tulband" because the flower resembles a turban.

Now, some trees do bear flowers resembling tulips. The more widely accepted common name "tulip tree" applies to the eastern U.S. native Liriodendron tulipifera (from the Greek "leiron" a lily, and dendron-tree; "tulipifera," tulip-bearing). So it's the "tulip-bearing lily tree," except no one calls it that. It is one of only two species in the genus Liriodendron. If you're a wood worker, or armchair wood worker like me, you'll hear the wood of this tree referred to as "poplar." But it isn't poplar, not even close (except perhaps for the look of the wood). That name is more properly applied to some trees in the genus Populus, which includes about 40 species such as white poplar, Lombardy poplar, cottonwood and aspen.

Is your head spinning yet? If not and you're still with me, magnolia (after Pierre Magnol 1638-1715, French professor of botany) is the scientific name of a genus of trees comprised of about 85 species of evergreen and deciduous trees and shrubs. Magnolia grandiflora ("grandi" = large; "flora" = flower) is the famous, broad leaf, evergreen Southern Magnolia, with the big white flowers. It's also known as "bull bay" in some areas, but that's another story.

On the other hand the deciduous magnolias include many species and hybrids. One of these is M. soulangiana (after Etienne Soulange-Bodin, French cavalry officer and director of the Royal Institute of Horticulture, who raised it). According to the "Sunset Western Garden Book" (which might be called the New Testament for fundamentalist gardeners) the term "tulip tree" is "erroneously" used for this tree. The flowers, which vary among the cultivated varieties, are generally purplish on the outside and white on the inside. They measure about 6 inches across when open, about the size of a saucer. Personally I can see the tulip more vividly than the saucer, but for the sake of clear communication, I use the common name "saucer magnolia" or the scientific name magnolia soulangiana.

In short, tulip tree is a widely accepted common name for Liriodendron tulipifera, while saucer magnolia is a widely accepted common mane for magnolia soulangiana and similar varieties within the species.

According to the "Dictionary of Plant Names" (Allen J. Coombes, Timber Press 1985) which I've used liberally above, "a scientific attitude was first taken toward the naming of plants in the 15th to 17th century, when Latin was common language among the intellectuals of Europe and it was second nature for many to use it Š"

Then around 1737 Carl Linn (later known as Carolus Linnaeus) the renowned Swedish botanist, began to publish his work, formally systematizing the taxonomy of botany and zoology. Based on sexual characteristics of flower parts, Linnaeus' system made it possible to make sense of the extremely complex and confusing world of living things and their relationships to each other in terms of Genus and species.

Today botanical names of plants are "governed by internationally accepted rules found in the International Code of Botanical Nomenclature. But common names "are not governed by any formal code of nomenclature" (Hortus Third, L H Bailey Hortorium, Cornell University).

Scientific names can be useful across barriers of nationality, language and time. Even so, they can change. Many is the time I've referred to my new copy of the Sunset Western Garden Book and found that a scientific plant name I memorized many years ago has been changed to something else. Reluctantly, I accept that. It's good for the little gray cells to learn something new, as science keeps moving forward. But with common names, beware! It's a jungle out there.

Bill Pramuk is a registered consulting arborist with Britton Tree Services Inc. Please send questions to bpramuk@pacbell.net