When I was very young, the aromas of the apricot orchard across the street, where San Tomas Park now is, changed with the seasons. 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 that every native to the Santa Clara Valley would recognize.

Few garden enthusiasts appreciate foliar aroma, but many enjoy foliar color of various deciduous species during autumn. Local climate is not conducive to the impressive foliar color that may 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 that grows on the sound walls of freeways is a climbing vine that exhibits excellent autumn foliar color.

Just as puppies grow up to be Dalmatians, young trees 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 concrete.

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. Consistency and texture of 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 wind. (The very fine, bipinnately compound foliage of silk trees and locusts are the worst!) Large leaves that are abscised within a limited time, such as those of the fruitless mulberry, are easiest to rake. Leaves of the American sweetgum trees (liquidambar) are large and easily raked but may fall from trees for several weeks or even into winter. Such trees provide color for an extensive duration but require periodic raking until all the foliage is gone.

Just as spring bulbs must be planted now for spring bloom, trees must be established in the garden before they can produce autumn color. Those who want autumn color next year should install new trees this winter. Trees planted now will defoliate as they should but are not likely to produce impressive color. Cool weather stimulates dormancy, but the stress of previous confinement of roots may stimulate premature defoliation.

Every species requires specific weather conditions of temperature and humidity to express foliar color. Liquidambar and Chinese pistache for example, seem to color well even during mildly cool weather. Modesto ash, however, does not color as well without sufficiently cool weather.