The very distinctive aroma of smoke from burning pruning debris through winter is perhaps what I miss most because it is the most difficult to duplicate without apricot trees. The profusion of bloom in spring smelled sweet and slightly pungent. In summer, the orchard smelled like overripe or rotting fruit. Then in autumn, the yellowing foliage exuded a very distinctive aroma that is impossible to describe, but one that every Santa Clara Valley native would recognize.

Few garden enthusiasts appreciate foliar aroma, but many enjoy the foliar color of various deciduous species during autumn. Local climate is not conducive to the impressive color that can be seen among such a broad range of species in New England. However, many species color reliably, regardless of mild weather.

Trees are the most popular providers of autumn foliar color, but a few species of shrubbery also color well. Boston ivy, which grows on the sound walls of freeways, is a climbing vine that exhibits excellent autumn color.

Just as puppies grow up to be dogs, saplings grow up to be—trees! Because each tree species expresses very specific characteristics, selection is very important to identify those that will not only provide color but will be complaisant with environmental conditions or restrictions. For example, trees to be installed between the sidewalk and curb should be complaisant with concrete and not produce voracious roots that will easily damage the pavement.

Deciduous trees are generally not as messy as evergreen species because foliage abscises and falls within such a limited season rather than throughout the year. When it does fall, it must be raked. The consistency and texture of foliage should therefore also be considered when selecting trees. For example, compound leaves that deteriorate into finely textured foliar litter are not as easily raked for removal but are more easily blown about by the wind. (The very fine, bipinnately compound foliage of silk trees and locusts are the worst!)

Horticulturist and arborist Kevin Raftery will conduct a lecture concerning autumn foliar color and a corresponding walking tour of Gamble Garden and the surrounding neighborhood in Palo Alto on Oct. 27 from 2 to 4 p.m. Many of the most reliable providers of color for mild climates will be discussed. More information can be obtained by calling 650.329.1356 or visiting www.gamblegarden.org.

On Oct. 26, from 10 a.m. to 2 p.m., Annie Hayes of Annie's Annuals in Richmond will be discussing species that may be planted now for spring bloom. On Oct. 27, the Midori Bonsai Club will conduct "A Day of Bonsai: Beginners' Clinic and Workshop" from 9 to 11:30 a.m., followed by a bonsai demonstration and show from 12:30 to 4:30 p.m. These two events take place at Yamagami's Nursery at 1361 S. De Anza Blvd. in Cupertino. For more information, call 408.252.3347.


Tree of the Week: California black oak

The California black oak, Quercus kelloggii, is native to the Santa Cruz Mountains but is not often seen in refined landscapes. It is, however, more tolerant of dense soil and irrigation than the coast live oak, which is more common but much less tolerant of garden environments. Black oak trunk and limb structure is irregular and eventually grows to 30 feet or taller.

The furrowed bark is dark brown and becomes darker during rain. Autumn foliar color is yellow but somewhat subdued. New foliage emerges pink but matures to deep green and resembles the foliage of the red oak. Individual leaves are approximately 4 inches long and 3 inches wide, with deep and angular lobes. If the soil is not saturated, the roots are deep and rarely damage concrete.

Because the California black oak is not common, it may be difficult to locate in nurseries. Like all oaks, smaller specimens become established in a new environment more readily than larger specimens. Trees in No. 5 (5-gallon) or even No. 1 (1-gallon) cans are preferred where possible. Trees in No. 15 cans may be installed where the durability of larger specimens is important, such as at the curb or in an area of significant traffic. Larger sizes become established more slowly as they recover from previous root confinement. Trees from No. 1 cans easily grow larger than trees planted from 24-inch boxes at the same time.

Horticulturist Tony Tomeo can be contacted at 408-358-2574 or at LGHORTICULTURE@aol.com.