Cold-hardy shrubs

Asked October 3, 2014, 7:00 PM EDT

After this past freezing winter, what cold-hardy shrubs can I plant around my house. Is there a resource I can look to. I'd love to plant natives but mostly need to choose plants that can handle the cold.

Benton County Oregon

1 Response

Wow. That is a good question. I will lead off with last winter was an exceptionally cold winter for the Willamette Valley. Many trees and shrubs were damaged or killed by this exceptional weather. I don’t know what kinds of shrubs you lost but there are several commonly used in landscaping here that are impacted even by our ‘normal’ winter temperatures. This area is rated by the USDA hardiness zone map as being in Zone 8b. This means that the AVERAGE minimum temperatures are not below 15-20 degrees Fahrenheit. Temperatures dipped below zero several times last year with days that did not get above freezing; that would have put us into a Zone 5 or 6 hardiness zone. When replacing your shrubs buy plants that have a hardiness rating of at zone 8b or lower. Many plants are viable over a range of hardiness zones. Based on the weather last winter you should buy plants that cover a range of say 5-7 or 5-8 or lower. Plants usually come with this information on their tag. If it is not on the tag ask your nurseryman to look up the hardiness of the plant prior to purchasing it. Now let’s talk about right plant right place. Plants planted in areas that are not their ideal type of location in the garden and not really thriving because of that will be more vulnerable to succumb to extreme weather. Be sure that the needs of each plant are met as closely as possible. Parameters such as the amount of sunlight, the amount of water and soil type impact the health of each plant. Now about microclimates. It is possible that your location is in a frost pocket which could mean that your temperatures actually are a little lower than surrounding areas. Microclimates can be created by many factors such as a rock wall that faces south and catches and retains more heat than the surrounding spaces in the garden. In addition the north facing wall of a home gets less sun and does not warm up nearly as much on a cold day in the winter. I have such a frost pocket that will retain frost on the ground most of the day in the wintertime. Being in a heavily wooded and therefore shaded place will keep the area cooler because the sun does not have as much a chance to warm the area in the winter. By selecting plants that can withstand a range of temperatures you will increase the chances of them surviving. Finally our ‘normal’ weather is a bit schizophrenic extremely wet all winter followed by extreme drought most of the summer and into fall. Native plants may be a good fit because they have evolved with this in mind, however if they are not planted in the right spot may not survive. You asked for a reference and I have one for you. The American Horticultural Society’s “Northwest Smart Garden Regional Guide.” It provides lots of suggestions for different gardening conditions and provides pictorial suggestions as to what to plant there. Examples are a chapter on ‘Shrubs for dry soil and sunny sites’ or ‘Shrubs for Clay Soils’. Photos of suggested plants are shown as are the ideal growing conditions AND the hardiness zone information that the plants will survive in. I will close with a suggestion to plant NOW. Fall is a great time to put in shrubs. Keep in mind that next summer during our typical drought you need to water them deeply at least once a week to ensure that they get fully established. This includes even ‘drought tolerant’ plants. After the first year they should be fully established and able to survive under our ‘normal’ conditions.