landscape zones in Oregon explained

What is the Deal With Landscaping Zones?

Every spring when it is time to start planting, the questions come out about what landscaping zones mean exactly. Today, we’ll explain what landscaping zones mean, particularly to those of us here in the Pacific Northwest.  Plant Hardiness Zone Maps were made by the USDA (United States Department of Agriculture) to help growers determine what plants will flourish in their area. Here is what the map of the entire United States looks like.

USDA hardiness map for landscaping zonesTechnically speaking, the map maps out zones based on average temperatures for the area. All landscaping zones are divided by 10 degrees Fahrenheit. The zones are based on average temperatures over the past 30 years and do not reflect the coldest temperatures ever recorded or account for the coldest possible temperature in the future. It is important for growers to keep that in mind when considering planting plants that are not rated specifically for their landscaping zone. If you are a new gardener, we always recommend staying with plants recommended for your landscape zone. Here’s what the map for our state of Oregon looks like. For those of us situated around the Portland area, we fall within the 8B landscape zone, or plant hardiness zone.


A Word About Microclimates

Microclimates are small areas that have fine-scale climate variations. Good examples are areas around blacktop, concrete, or small hills that can cause cool spots in your garden. Every yard or landscape is different, and it is important to note any microclimates you may have on your property. In addition, it is possible that your entire yard could be part of a microclimate. This happens most often when a yard is sheltered or very exposed. There are a few other factors that can change a gardener’s idea of what they should or should not plant.

Other Factors to Consider When Choosing Plants

  • Light – Plants always need to be sure to receive the proper amount of sun and the amount of sun a place in your yard receives can vary greatly between summer and winter depending on your area and the amount of shade. Consider what temperature variances can happen in both the summer and winter in accordance with the possible amount of sun before choosing to plant something on the fringe of your hardiness zone.
  • Soil moisture – This is usually not a problem in Oregon, but occasionally soil with too little moisture can affect how well a plant does in a particular zone.
  • Temperature – Pay attention to the optimal temperature range for a specific plant. While some plants can handle varying temperatures, others cannot. Be aware before you plant what temperatures a specific plant can handle.
  • Humidity – High relative humidity limits cold damage by limiting moisture loss from sensitive parts of the plant (leaves, branches, and buds). Cold injury can be more severe if the humidity is low, especially for popular in Oregon, evergreens.

To make the best choices about plants in your landscape, use your knowledge of landscaping zones, microclimates, and the other factors listed above.  Or, if you ever feel that you are in over your head, always feel free to ask a  professional. If that is already the case, you are in the right place! All Oregon Landscaping is full of landscape experts who can help you determine the best plants for your yard, microclimates and all. Don’t hesitate to shoot us an email or give us a ring!

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