It’s official! We are now in USDA hardiness zone 8b. Are we really? Twenty five years ago, when I was studying Landscape Design, my professor said something I’ll always remember. “People think that we have mild weather here in the Pacific Northwest, but every four to six year we get walloped by Mother Nature.” I’ve been observing the weather ever since. He was right. Since 1990 we’ve had ten different years where the temperature dropped below the 20 degree mark; the high end of zone 8b. But the story isn’t just low temperature. It’s also duration of the cold snap. Many 8b plants can handle a day or two of below 15-20 degrees, but when we get a cold snap that exceeds three days, our precious plants start dying.
The bottom line: If you like the tropical look or have a favorite plant that’s a little on the zonal edge, go for it! Just plan on the possibility of occasionally replacing it or having to whack it down to the ground and hope it comes back. I adore New Zealand Flax. It is said to be zone 8. I’ve grown them for a few years and then they get frozen out. Some are hardier than others but it’s still risky. I continue to put them in designs but I warn the client that it’s a great plant and well worth replanting when it gets stricken down.
If you are more interested in having a low maintenance garden, then go for lush but hardy plants. I try to stick with zone 7 or colder plants. If you must walk “on the wild side” use zone 8 plants very sparingly and stay totally away from zone 9 unless you like hauling big pots into your garage. I gave that up years ago along with hauling benches in for the winter. I know there is a lure to test how far you can go, but remember those who go where others fear to tread just might get their plants frozen.
Ann has lived and practiced landscape design in Tualatin Valley since 1993. Please feel free to contact Ann via email – firstname.lastname@example.org or by phone at 503-846-1352 with your comments or questions.