There are few places on earth that have a desert climate with scant summer precipitation, but also have a large river running smack through the middle. The Nile River and Egypt come to mind.
This geographical rarity is even less common if you are looking for areas that have moderate summer temperatures and real winters. So, Egypt is out.
Only tiny specks of the earth’s total surface, including central Washington, meet these special conditions. Those temperate desert-with-river areas also include parts of southern Chile and some regions in north central Turkey that look very similar to central Washington. These rare regions are special for many reasons, including that they are an easy climate to live in, but also that they are exceptional areas to grow temperate-climate tree fruits.
To be near perfect, these fruit production areas must have moderately cold winters.
Cold weather is necessary because it triggers dormancy in fruit trees, but severely low temperatures can kill a fruit tree or damage the flower buds before they open. The Christmas/New Year season of 1968-69 set the record for low temperatures in Washington (-25F in Wenatchee, and a reported -40 to -50F in other areas of eastern Washington.) This almost killed the tree fruit industry in some areas of the state, such as the Winthrop region, because few fruit trees can tolerate -40F. Fruit flower buds were not killed directly by these low temperatures, but many fruit tree trunks died. Growers saved many by “arch grafting” live tree branches over the damaged parts of trunks, and a few of these repaired trees remain alive to this day.
Winter must be cold enough to send a clear signal to the tree that it remain dormant, at rest. Full dormancy and their deepest degree of cold tolerance is usually acquired by Christmas, and warmer temperatures any time after that will accumulate and signal the tree that is should slowly break dormancy, becoming less hardy as the warm days add up.
Some other tree fruit production areas with warmer winters have trouble getting their fruit trees fully dormant. This leads to scattered blossoms opening for two or three weeks, instead of the optimum few days. This drawn-out bloom period leads to uneven fruit maturity. Also, without proper winter chilling, different varieties of the same tree fruit may bloom weeks apart in the spring, complicating pollination and fruit set. Areas that have this issue include tree fruit production areas of north central Mexico, Chile, California and South Africa.
All of this leads to advantages for central Washington, with a tree fruit blossom time that is probably the best anywhere in the world. The first to bloom are apricots, with showy mid-pink flower color. A few days later, the plums produce a blizzard of small white flowers. Then the pink peach and wildly pink nectarines come out, followed by the fluffy pink-white cherries and the light greenish-white pears, and finally, the apple blossoms that put on a show with pink highlights on white.
Timing for all this display occurs late March to mid-May, depending upon the warmth of the year’s spring weather and the orchard’s elevation. The date of apple full bloom in Wenatchee has varied wildly (April 9 to May 16) over the 86 years of monitoring at the WSU Tree Fruit Research Center in Wenatchee.
Unfortunately, the Wenatchee Apple Blossom Festival timing rarely lines up well with the April 27 long-term average full bloom date in Wenatchee. However, it was a close match this year. It was nice to have apple blossoms around for this year’s festival. The “little green fruit” festival just wouldn’t sound right.
A WSU Master Gardeners of Chelan County column appears weekly in The Wenatchee World. Tim Smith is one of four columnists featured.