Malus is a simple name for the trees that produce apples, but oddly means "something bad," perhaps because of that unfortunate event in the Garden of Eden. Pyrus is an equally simple name for pear that means "something that burns." This could be a result of fiery autumn foliar color, or susceptibility to fireblight.

Latin is the only universal language of horticulture. It is used for nomenclature because common names and horticultural slang are so regional. For example, Acer platanoides, which means "maple with sycamore foliage," is known locally as Norway maple, but in parts of England is known as a sycamore. Platanus acerifolia, which means "sycamore with maple foliage," is known locally as London plane or sycamore, but is a maple elsewhere.

Contrary to what I would prefer anyone to believe, local common nomenclature is not always accurate. Californians classify some of the species of Eucalyptus as gum, ironbark, yate, peppermint or mahogany. More complete Australian classification would include such amusing names as box, coolibah, moort, marlock, mallet, mallee, sally and gimlet. I would have guessed that a moort and a gimlet could be found in a small plastic bag inside a dressed turkey. Latin is simply more reliably accurate and less confusing than common names are.

The nomenclature used at retail nurseries is, of course, a combination of Latin and common names. Local lingo is appropriate for local establishments. Latin or botanical names become more necessary when researching particular species online or in horticultural publications. Fortunately, most such publications include an index of botanical names listed by the more common of common names, to help everyone be "on the same page."

Common names are not the only locally distinct horticultural concern. It is also important to be aware of environmental variables. Fortunately, descriptions of at least some of these variables have been standardized. The two most important of these concerns are climactic zones and soil pH.

Most everyone in at least western North America uses the same numeric designations for climactic zones, and similarly standardized designations of soil pH. It is simple enough to determine if the environmental preferences of any particular species will be accommodated by any particular garden. This is what prevents garden enthusiasts in Portland from planting tropical palms that would be perfectly happy in Los Angeles. It also reminds us that the alkalinity of endemic soil will cause hydrangeas to bloom pink. Soil must be acidified for bloom to be as blue as it would be in western Oregon.

Generally, soil within the Santa Clara Valley is slightly alkaline and dense. Some areas of rocky alluvial soil drain better. The Sunset climate zones are 15 and 16, or 17 near the Bay.

Flower of the Week: Sunrose

Helios is "sun." Mum is "flower." Helianthemum nummularium should therefore be a sunflower, but is not. It is the name of sunrose, a small shrubby perennial that is generally less than six inches high and two feet wide. The single or double flowers may be red, orange, yellow, pink, white or pinkish orange. Individual flowers last only a day, but are replaced as quickly as they fade. Bloom begins in April and is mostly finished by mid-June. Shearing after bloom promotes secondary autumn bloom. The dark or grayish green leaves are less than an inch long.

Sunrose needs full sun exposure and good drainage. It can rot if irrigated too frequently. Although sunrose can be grown in containers, it is happiest in the ground, where it can disperse roots more extensively. It is useful in spaces that are too tight and too exposed for other species.

Sunrose is available in No. 1 (1 gallon) cans or smaller sizes. Once acquired, it should be planted as soon as practical because roots are more likely to rot if left too long in non-porous black vinyl or plastic nursery cans, particularly if warmed by the sun.

Horticulturist Tony Tomeo can be contacted at 408.358.2574 or at LGHORTICULTURE@aol.com.