phenology n. “The scientific study of periodic biological phenomena, such as flowering, breeding, and migration, in relation to climatic conditions.”

The cherry trees in Washington, DC are expected to bloom later than usual this year. This means that the peak bloom should occur smack-dab in the middle of the 2009 National Cherry Blossom Festival. The festival producers and sponsors are understandably very happy. Spring weather being what it is, however, you just can’t rule out disappointment.

When Tokyo’s mayor Yukio Ozaki presented President Taft with a gift of 3,020 Yoshino cherry trees for our nation’s capital in 1912, he could scarcely have imagined that the U.S. Army Air Force would be bombing his homeland just 30 years later, or that his generous gift would provide the focal attraction for what has become one of the world’s most renowned festivals. Fate truly does take some odd twists and turns.

The salient facts here are these:

• Cherry trees produce pink blossoms that are drop-dead gorgeous.

• The bloom occurs in the early spring when northerners are damn sick and tired of winter and ready to celebrate the end of it.

• The gift trees from Japan were added to 90 cherry trees already in place on the Tidal Basin rim, adding a burst of spring glory to what was already one of the world’s most scenic promenades.

• The District inaugurated a cherry blossom festival in the spring of 1935 when the Great Depression was in full swing.

• This celebration of spring beauty, now dubbed the National Cherry Blossom Festival, has since blossomed into a mega-event that attracts three-quarters of a million people a year to the Tidal Basin vicinity and entertains them with a lavishly funded calendar of activities and attractions.

While the cherry trees rimming the Tidal Basin get most of the publicity, there are also a good many trees in the Washington Monument vicinity of the Mall and at Hains Point.

Whoops! There are some more salient facts. On average, Washington's cherry trees blossom for about ten days in late March/early April, with a peak (at least 70% of the trees in blossom) that lasts for about three days. However, cherry tree blooming is a very weather-dependent thing, being sensitive to the harshness of winter and to the onset and duration of warm and cold spells as winter transitions to spring.

It goes without saying that festival producers and festival-goers want the best color display to occur during the festival. Having moved to a two-week format 15 years ago, the festival now runs 16 days. This year it’s scheduled for March 28th to April 12th.

Unfortunately, the blossom peak could come earlier or later than usual, and it’s not written in stone that it has to occur during the festival (which must, after all, be scheduled way in advance). The weather that Washington, DC, gets in the late winter and early spring is brewed up in the continental interior and is notoriously fickle. This year’s festival could have weather ranging anywhere from sunny and warm to cold and blustery. Even snowfall can't be entirely ruled out. These are thoughts that keep festival producers awake at night.

The National Cherry Blossom Festival, Inc. is the event producer. The event sponsors, participants, media partners, and other supporters comprise a long list that includes the National Park Service, the D.C. Economic Partnership Office, the Japan-American Society of Washington, DC, the Japanese Embassy’s Ministry of Public Affairs, and many others.

Imagine how happy the big worriers were when National Capital Region chief horticulturist Robert Defoe recently informed them that this year’s blossom peak is likely to occur somewhat later than usual, probably around April 3rd to April 9th. That’s right in the festival sweet spot.

It’s time for high fives alright, but don’t bet the farm. Forecasting the blossom peak is an inexact science, and weather vagaries being what they are, it probably always will be. That said, the confidence level is fairly high this year. The winter was colder than usual and recent weather has been nasty. Both of these facts incline the trees toward delaying the budding-and-blossoming cycle.

If you’ve always had a yen to attend the National Cherry Blossom Festival, this just might be the year you’ve been looking for. Or not.

Postscript: Washington's cherry trees, like people, grow old and eventually die. In fact, by the late 1990s fewer than 200 of the original trees were still alive. Fortunately, replacing dead or dying trees is a fairly simple matter. Lady Bird Johnson accepted an additional gift of 3,800 cherry trees from Japan in 1965. Ten years ago, additional plantings were made with cuttings obtained from a renowned (and extraordinarily long-lived) Japanese tree.

Traveler tip, no extra charge: If you can’t make it to DC, then consider going to Macon, Georgia, instead. The National Cherry Blossom Festival gets all the press, but Macon has more cherry trees – vastly more -- than you’ll ever see in Washington. Macon, which has been hosting the International Cherry Blossom Festival since 1983, has at least 300,000 Yoshino cherry trees. (In true American fashion, Macon boosters brag that they throw “the Pinkest Party on Earth.”) This year’s International Cherry Blossom Festival is slated for March 20-29.