I had ignored it for a few minutes, unaware that I was actually awake, but as the frequency of the popping accelerated and I realized what it was, I ran to the window just in time to see about half of a very large valley oak tree fall into the neighbors' swimming pool and onto a large garage of another neighboring apartment building! Fortunately, no one was hurt, but among the several cars in the garage that had not been damaged, a new 2002 Saab had been impaled and is still stuck to the garage floor like a scarab in an insect collection.

The property management of the apartment building contacted arborist Larry Cook of Absolute Tree Care, an associate of many of my associates. During his visit, I was reminded of the importance of proper tree care. The tree he came to inspect had not been damaged by "hackers" like so many others have, but could have benefited from modern cabling and weight reduction. Previous cabling had utilized materials that were acceptable in the late 1950s but inadequate by contemporary standards.

I realize that I discuss arboriculture more than any other garden columnist, but it is likely the most important concern in gardens inhabited by trees. Most gardening mistakes can be corrected. For example, annuals of objectionable color need not be planted the following year. Perennials, shrubbery and even young trees may be removed and replaced if they are found to be inappropriate. A new Saab or an oak three centuries old are, however, not so easily replaced.

It is, of course, very important to only procure the services of qualified arborists for maintenance of trees. Unqualified arborists or "hackers" can cause irreparable damage. It is also very important that regular gardening activity be conducive to the healthy development of trees. Because cultural preferences of trees are different from those of other specimens in the garden, compromise is often necessary.

Most garden enthusiasts are aware that established oak trees may be easily damaged by increased irrigation. Most other tree species are likewise sensitive to irrigation. Unnecessarily frequent or generous irrigation can maintain saturation in lower soil strata, inhibiting development of deep roots. Development of surface roots is consequently enhanced. Unfortunately, surface roots are much more likely to damage surface concrete or become damaged by excavation or irregularities of irrigation. This is perhaps the most common cause of arboricultural problems in areas where dense soil drains slowly.

For those who did not see my column last week, the city of San Jose, the San Jose Public Library and Friends of the Willow Glen Library have arranged for me to conduct a brief lecture free to the community on Oct. 8. The main topics to be discussed include selection of nursery stock and basic pruning techniques, but questions are encouraged throughout the lecture. There should also be time afterward for questions concerning other topics. The lecture will be at the Willow Glen Library, 1157 Minnesota Ave. in San Jose, starting at 7 p.m. For more information, call 408.998 2022.


Flower of the Week: Cape plumbago

The cape plumbago, Plumbago auriculata, is not quite certain if it wants to be a vine or shrubbery. The limber stems may accumulate into a thicket about four feet high and twice as wide. With support on a trellis or fence, stems may extend to 10 feet high. The 1-inch-long leaves are light green and may be sensitive to frost.

Regardless of the awkward form, plumbago is popular because of the clusters of clear, light blue flowers that are only absent in late winter.

Most are grown from cuttings, but those grown from seed may bloom in shades of blue ranging from light sky blue to almost white. The cultivar 'Alba' (grown from cutting) exhibits white flowers. With adequate drainage, inferior soil is easily tolerated. Regular irrigation is preferred but not necessary for established specimens. Young plumbagos may grow slowly, but become more voracious with maturity.

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