Bill, There is a tree on the 300 block of Franklin Street, west side, the block where the big redwoods are growing along the street. It is large and has orange flowers. What is it? I’ve never seen one before.  It’s driving me crazy!  It is blooming as I write. The only tree I know in this area with orange orange flowers is the pomegranate. - LF

Dear LF, I love mysteries regarding tree identification, so when I received your message I took the first opportunity to drive by and have a look.

The tree is a “red-flowering gum”: Eucalyptus ficifolia, a rare specimen for Napa. The genus  — Eucalyptus —  seems to be almost infamous now-a-days, as “eucs” have become problematic in some areas. The species — ficifolia — is so named because the leaves resemble those of some species of Ficus. That genus includes common figs and many trees and house plants.

Checking  the most recent edition of the Sunset “Western Garden Book,”  I noticed  that “some botanists now divide Eucalyptus into several genera.” It never ends! Red-flowering gums are now classified as Corymbia ficifolia. Most of the other species, including the well-known blue gum, are classified as Symphomyrtus.

In the San Francisco Bay Area, red-flowering gums are seen more commonly in cities near the bay, where winter low temperatures are milder than they are here in Napa Valley. I’ve seen some nice specimens in San Francisco. When I worked in the wholesale nursery business we did a large “contract grow” of them for a city by the bay.  

The difficult part of the contract was that the city wanted the trees all to have red flowers, no orange, pink or cream. That was very tricky, since the trees were grown from seed and the natural variability of seedlings produces  a range of flower colors. The specimen by Franklin Street is a seedling that just happened to  get the orange gene.

Red-flowering gums are not cold-hardy enough to be reliable in general around the valley.  Although I never saw it, this one probably looked dead after the big freeze of December ’90. If it was was badly damaged, it recovered beautifully.

When we’re talking about trees and other plants, the term “hardy” or “hardiness” is best used in reference to tolerance for cold temperatures, though people often use the term for vigor, vitality or sheer toughness. It can cause a glitch in communication when someone asks if a tree is “hardy.” Do you mean “vigorous survivor” or “tolerant of our local low temperatures?”There is a big difference.

It was a surprise to see this big red-flowering gum, since they are hearty but not “hardy!”

Cold tolerance is affected by several factors: genes, the age and vitality of the plant, root zone moisture and the seasonal timing and duration of cold temperatures. Even plants that are very hardy can be badly damaged by an ill-timed sudden freeze.

Euclypts (that’s the plural for Eucalyptus), are a part of California botanical history, having first been planted here more than 130 years ago. They offer astounding variations in size, form, color and ability to survive drought, floods, difficult soils — even cold temperatures.

Although many of them are too large for most suburban gardens, they deserve a well respected place in California’s history and future.

Bill Pramuk is a registered consulting arborist. Visit his Web site, www.billpramuk.com, e-mail questions to info@billbramuk.com, or call him at 226-2884.