WSU Extension Q&A: Rhododendrons hard to grow east of the Cascades

Even though rhododendrons are Washington's state flower

WSU Benton County ExtensionMay 1, 2014 

Q. I moved here from the Seattle area and want to grow some rhododendrons, but a friend told me they are difficult to grow in the Tri-City area. Why?

A. It is unfortunate that the state flower of Washington is a challenge to grow in many parts of the state east of the Cascades. Rhododendrons are ericaceous plants (along with blueberries, heather and azalea) that grow best in well-drained acid soils (pH of 4.5 to 5.5) that are high in organic matter. Since most of our local garden soils are alkaline with a pH of 7.5 and above, rhododendrons do not have a chance of growing well unless the soil is modified to provide acid soil conditions. This can be accomplished by growing the shrubs in raised beds with significantly modified soil.

However, even if you are able to create a bed with acid soil, our climate also makes it hard to grow healthy rhododendrons. Intense summer sun, extreme heat, low humidity and drying winds along with cold winter temperatures are not favorable growing conditions for rhododendrons that prefer a more moderate coastal climate, like Seattle. Why torture rhododendrons when there are many other beautiful flowering shrubs that can be grown with ease in this region?

Q. I started my vegetable seedlings indoors. What is the best time of day to move them into the garden? Should I just transplant them outside when I'm ready?

A. No, it is best to "harden-off" the plants before transplanting to the garden. This can be done gradually by placing the plants outside in a protected area for a few hours each day and then bringing them in at night. Increase the time they are left out each day for about a week before transplanting into the garden. It is best to plant transplants in the evening or on cloudy days to reduce stress-induced wilting.

Q. The kids in my 4-H group love bugs. What kind of projects can we do?

A. Entomology is the best bug project out there. We have a great new national curriculum to guide parents or volunteers through the scientific process of exploring bugs through hands-on learning. Find more information about this fun project from the WSU Franklin County Extension Office at 509-545-3511 or by emailing

-- Questions should be called in to the WSU Extension offices in Kennewick at 735-3551 or Pasco at 545-3511.

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