California sycamores, like these two near Wildwood Park in Saratoga, live several hundred years and grow to be large, gnarled, distinctive trees.




Photograph by Shari Kaplan







Fair or foul, flowers have reasons for their scents

By Tony Tomeo

Those who read this column regularly are probably aware of the rivalry between my colleague Brent Green and me. I have always been involved in the agricultural/horticultural production industries.

If I was to landscape my garden, it would probably resemble row crops with an orchard. Brent, however, is a landscaper and enjoys design. His garden is too elaborate for my taste. In fact, I would say his garden stinks. I mean that quite literally--there is an overabundance of fragrant flowers and foliage that can be overwhelming on warm, humid days.

Perennial plant species with fragrant or "aromatic" foliage, such as sage, rosemary and thyme (and according to Simon and Garfunkel, parsley) are often used specifically for their fragrance and as culinary herbs. Incense cedar, camphor, cypress, eucalyptus and pine are examples of some trees that exhibit aromatic foliage. Juniper, lavender and myrtle may be used as aromatic shrubbery.

Brent suggests using such species close to walkways or traffic areas where they can be appreciated. The fragrance of most is more noticeable if the plants are brushed against by visitors. Brent has even planted sage behind a gate where it is struck when the gate opens.

Fragrance in flowers is as variable as the plants that produce them. Generally, if a flower is fragrant, it is trying to attract a vector to pollinate it. Although many species have several potential vectors, each has a "vector of choice" to which it tries to be the most appealing. Flowers that primarily attract bees are usually more profuse and often mildly fragrant.

Strongly sweet fragrance from fewer flowers is usually used to attract bats. This is why such flowers are most noticeable on warm evening. Many plant species are endemic to areas with different vectors that are not present here. However, they continue to produce the fragrance that was so effective back home--sad if you think about it. There would not be such variability in fragrance if all flowers were designed to attract the same vector.

Incidentally, there are a few flowers that are pollinated by flies, generally in the family Araceae. Fragrances attractive to flies, however, are not so appealing to people. Fortunately, most fly-pollinated species are grown for their foliage and the flowers may be removed before they open. The most common plants from this family are philodendrons, which are usually maintained in their juvenile state and do not bloom.

Because aromatic flowers are designed for their vectors, they also try to bloom when the vectors are most active. Those that use insect vectors usually bloom after there has already been some degree of warm weather. Earlier blooms cannot be serviced if the vectors are still dormant or pupating. The same warm temperatures that stimulate activity among insects also stimulate increased fragrance in flowers.

Flowers that prefer bats may stop producing fragrance and even close their petals during the day while bats are resting. Many cacti produce flowers that are open all night for bats and moths. Some cacti even engage in rather creative advertising. Their translucent petals reflect ambient moon- and star-light, which guides moths to the source of the fragrance.

Tree of the Week: California sycamore

The native California sycamore, Platanus racemosa, grew well in the soils and climate of the Santa Clara Valley long before it appeared in landscapes. These trees can get very large, up to 80 feet, so are usually only planted in large landscapes. However, mature trees are often included in gardens as the area surrounding them is landscaped. They tolerate irrigation better than most natives, but may eventually experience problems in dense soil.

Branch structure is distinctively irregular. Their gnarled appearance results from years of combating various pathogens, which include spider mites and anthracnose. Trees are usually not sprayed, because without these naturally occurring pathogens, the canopy would be too heavy to support.

The problem with this symbiotic relationship is that pathogens may affect more sensitive species in the garden. Leaves raked in autumn should be disposed of because spores overwinter in them.

Trunks and limbs are very large at maturity. Bark is interestingly smooth and blotchy. Good examples of this tree may be seen in most Santa Clara Valley creeks and at Vasona Lake County Park in Los Gatos.

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Horticulturist Tony Tomeo can be contacted at 408.358.2574.

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