The good news is that you can grow cherries on the Olympic Peninsula. The bad news is they may not always fruit well.
Learning a little more about the cultural requirements of any tree you’re planting is always a good idea and doing so can help eliminate, or at least reduce, potential problems.
The Stella cherry (Prunus avium ‘Stella’) is a great tree for our peninsula — it likes sun and deep, fertile, well-drained soil.
Cherry trees have fairly shallow roots and in the dry summer they usually require supplemental water. A deep watering every 10 days is suggested. To retain moisture mulch is recommended. Any type of mulch is good as long as you can clean effectively under the tree in the fall and spring.
Site selection is important, so avoid planting a cherry tree too close to a heavily trafficked area, such as a gravel driveway where soil compaction could be a problem (remember the shallow roots).
The Stella variety will do best in full sun with at least six hours of direct sunlight in the warmest part of your garden. In partial shade they will yield less fruit. If an existing cherry tree is being shaded by other trees in your yard, some selective pruning to the other trees to increase the light may be needed.
Fertilizing home cherry trees can be tricky: too much nitrogen can cause excessive green growth. In addition, soil on the peninsula tends to be very high in phosphorus, so fertilizer may not be the answer. It’s unwise to recommend a fertilizer plan without first getting a soil test to determine pH and fertility (Stella perform best in a pH range of 6-7).
Details on soil tests can be found on the Clallam Conservation District website, clallamcd.org. The test results will give recommendations on fertilization and pH control specifically for cherry trees.
Lack of reliable fruit every year can be a problem and is usually caused by either wonky weather (not a technical term) or the tree is not being pollinated adequately. Even self-fertile trees need the movement of pollen between blooms.
As far as wonky weather, the Peninsula has its fair share. The critical factors here are location (elevation) and spring frosts. A late frost is one of the main hazards for cherry growers as cherry trees bloom early. Cherry trees are hardy but they are averse to sudden extremes in winter temperature. The buds are also susceptible to damage caused by a spring frost. Unfortunately, there is nothing you can really do about these weather conditions but to note them so you have some idea why the crop is different from year to year.
As far as pollination, bees are the primary agent. Few plants self-pollinate without the aid of pollen vectors (such as wind or insects). If a healthy bee population is not available during the pollination window, you will experience a decline in fruit. Bees are affected by cold weather, rain, high winds, smoke, and toxins.
Bees start to move around at about 55 degrees but really do their work at about 65 degrees Fahrenheit, which is when pollen is most effective.
Pollen may fail to germinate when temperatures are below 41 degrees Fahrenheit and pollen tube growth is extremely slow below 51 degrees Fahrenheit.
If there is a cold snap, fog, or you are located in an area where warmth is sometimes slow to come, that could affect the busyness of the bees. They also don’t like a lot of rain and high winds can make it hard for them to work; however, light wind can help with wind drift pollination.
Smoke from wildfires during spring is unlikely but do consider nearby burn piles as a possible problem.
Toxins are a big consideration if you are spraying the tree or nearby plants during the time bees are active. Even organic, natural, and Organic Materials Review Institute (ORMI)-listed products will kill bees and should never be used when plants are in flower.
Having more diverse insect pollinators would help pollination. Introducing Mason bees might be a good idea. Mason bees are not aggressive and they are wonderful pollinators that will work in cooler weather.
The best time to plant a Stella cherry tree is late autumn or early winter, so now is a good time to start preparing.
For more information on fruit trees, go to extension.wsu.edu/clallam and type “home fruit” or “fruit trees” in the search (symbol found on upper left) for a good selection of links from all over the state on fruit trees. While you are there, type “bees” into the search engine to get more information on Mason bees.
Susan Kalmar is a veteran Master Gardener volunteer.