At about a quarter to two the next morning, approximately a third of the massive valley oak above the carport collapsed onto the roof, which actually withstood the incredible weight dropped onto it, protecting all but one of the cars below. Unfortunately, the only large limb that penetrated the roof impaled and crushed the new Saab, as well as the concrete slab floor below.

Almost everyone who witnessed this was amazed that it did not happen on a "dark and stormy night" as would be expected, but on a warm, humid and windless night. I, however, had seen the results of trees' spontaneous limb failure many times before. I can sense among most who witness it that they do not expect me to believe their eyewitness accounts of this phenomenon, which seemingly occurs without provocation.

Spontaneous limb failure most often occurs during warm, humid and windless weather. Warmth enhances foliar expansion and vascular activity, which increases the translocation of moisture into the foliar canopy. The subsequent increase of foliar weight alone can exceed the supportive capacity of the limbs. Humidity and lack of air circulation inhibits evapotranspiration (evaporation of moisture from foliar surfaces), which would otherwise dissipate some of the excessive weight.

Some species are, of course, more susceptible to spontaneous limb failure. American sweetgum (Liquidambar styraciflua) and several species of eucalyptus are perhaps the most notorious. Coast live oak and valley oak are perhaps less susceptible, but because of their mass, can cause more damage. Italian stone pine, Aleppo pine, Atlas cedar and deodar cedar, as well as a few other species native to dry climates, may be very susceptible within an irrigated landscape.

As much as I like the various species of eucalyptus, I don't recommend them for small urban gardens in which any falling limbs are likely to land on something.

Flower of the Week:
Flower tobacco

Although I was known as Tony Tomato in high school, I am not even remotely related to the tomato family, Solanaceae. Contrary to the name of this interesting family, it is not remarkably prominent in Solano County, but is so within areas surrounding the Gulf of Mexico.

Solanaceae provides many vegetable fruits, such as tomato, pepper, eggplant, tomatillo and cotton (yes, cotton is a fruit), as well as tobacco and potato, which are true vegetables. Many flowering species are also within this family, such as petunia, blue potato bush, potato vine and angel's trumpet. Solanaceae also includes many very toxic species, such as gypsum weed and locoweed, which incidentally got its name by causing grazing cattle that ate it to hallucinate and go mad before suffering a painful death.

Flowering tobacco, Nicotiana alata, happens to be within the last of these three categories, as it is too toxic to be smoked or chewed. It also fits in the second category, because it provides colorful and fragrant bloom. Flowers resemble those of petunia, but are smaller and more tubular. Floral color ranges from white to red, including a few shades of pink and an oddly deviant shade of pale green. The exclusively white flowers of the wild species are closed during the day, but are larger and more fragrant than those of the more common varieties. Basal foliage is larger than foliage nearer to the bloom at the top of the plants.

Like petunias, flowering tobacco is sold in six-packs (cell-packs) or jumbo-packs (large cell-packs), and also may be grown easily from seed. Many garden enthusiasts who have enjoyed flowering tobacco for several years planted it once and collect seed every year afterwards. It grows well in full sun and tolerates some shade. Most varieties are shorter than a foot and a half, but the largest may be as high as 3 ¹/2 feet.

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