Sunset Western Garden Zones By Zip Code
Dixie Schlatter
But before you can ever ignore your garden zone you need to know it & how it helps you be a better gardener. Equipped with that knowledge you can choose to ignore it on the right occasions.
Monrovia uses the USDA map to classify their plants. Pop on to the Monrovia site & type in your zip code to determine your zone & find plants that will thrive there. Such an easy way to make a garden plan that will thrive.
I am in Sunset Zone 22. Well, I am pretty sure I am in Zone 22 based on looking at the map. However, I find the Sunset zones a bit overlapping & kinda confusing. It might suffer from a bit of TMI ( too much information ), but maybe that is just me.
The combo of the USDA map & the Monrovia site allows you to type in your zip code & search for plants in your hardiness zone. You can even just search your zone your once you know it & get suitable plants that way. Simple!
To use the map visit the USDA Plant Hardiness Zone Map. There is a static map page and an interactive map that can pinpoint to your zip code and give you finer details including microclimate information. Some areas of your greater neighborhood or geographic region may exhibit a different sub zone designation than your garden. These differences can be caused by a large hillside that deflects the prevailing wind, a lower topography than surrounding areas that can create colder air at ground level, a large body of water that could mitigate frosts, and other local topographical features to the site. Downloads of the USDA maps are available at the link above for your reference as well as some good, solid information about microclimates and how they affect gardening. Knowing your zone designation empowers you with knowledge when you are looking at plant labels and trying to determine if a prospective plant will thrive in its intended future home; most plant growers use the USDA zone information as reference on their labels.
Sunset, well-known publisher of the popular garden book for west coast gardeners, developed maps to enhance the use of the USDA plant hardiness maps. Their maps take into account more than just average extreme winter low temperatures, also measuring other climate factors such as the length of a growing season; timing and amount of rainfall in an area; summer highs and winter lows; wind; and humidity. Their maps have many more subdivisions indicating the more actual microclimates associated with our very versatile geography in North America. What is considered Zone 8b on the USDA map for the Seattle area is considered Zone 5 on the Sunset map. Their description of this zone includes references to our maritime climate, a definite influence on how our gardens grow. To use the map and access information for western Washington climate zones visit: Sunset Climate Zone Maps.
Knowing your soil temperature allows you to be informed about when it is time to set particular plants out into the garden. It also lets you know if the soil is too cold to be worked. This is especially true for vegetable gardens. Working soil when it is too cold is structurally damaging to the soil and certain food crops, like peppers and basil and tomatoes, prefer soil temperatures to be in the 60 F range for optimum growth. You can check on soil temperatures to see if they have become warm enough to plant your tomatoes out without damage.
Tracking the direction and speed of the wind in your area can aid you in protecting your plants. Basic knowledge of the direction winds generally come from in your area is useful for trellising and placing plants in the landscape. It can also be helpful in positioning plants to help provide windbreaks for your home or resting spaces in your garden! Real-time wind information can help you plan for future events by becoming aware of patterns. Be sure to check weather forecasts to protect plants from cold or heavy winds predicted for your area before they arrive.
NOAA also offers a chart showing the probability of frost or freeze dates for Washington. You can use this information to determine when your garden would be likely to encounter a 10% chance of seeing a 32o F temperature, helping you pinpoint an early, approximate date to plant cold-hardy veggies in the spring. You can also gamble and consider when there would be a 50% probability of seeing freezing temperatures to try an earlier planting, or at the end of the season check for when you might need to look out for a frost that could kill your basil. In contrast to the USDA map, which helps you choose plants that will survive your coldest temperatures, this chart helps you to plan when to plant in different seasons.
To learn more about Pacific Northwest gardening and helpful resources, contact the Garden Hotline at (206) 633-0224 or www.gardenhotline.org. You can also find us on Facebook, Twitter, Pinterest and YouTube.
The Garden Hotline is managed by Tilth Alliance and sponsored by Seattle Public Utilities, the Cascade Water Alliance, Seattle and King County's RainWise Program and the Hazardous Waste Management Program in King County.
Winter and spring are the seasons for planning, planting and envisioning new gardens and landscape designs. Garden centers are full of attractive flowers, shrubs, and trees. When selecting perennial varieties that will survive through winters in South Dakota, use the USDA Plant Hardiness Zones to help identify the best candidates for your landscape. Recent changes to the maps have South Dakota gardeners feeling adventurous. Learn how to proceed with cautious optimism by understanding what the USDA Plant Hardiness Zone updates mean for you!
The 2023 PHZ maps use the same calculation as the old Sunset zones. The calculation uses the average annual extreme minimum temperature for the years 1991 through 2020. This serves to identify thresholds of pests, disease, and plant damage due to cold temperatures. In South Dakota, over the last several decades, there has been a trend of warmer winter temperatures. As a result, many areas of South Dakota are now categorized in a higher number zone. Much of the state moved one zone warmer, for example from 4a to 4b or 4b to 5a. Zone 4 indicates average annual extreme minimum temperatures of -30 to -20 degrees Fahrenheit. New on the map in 2023 is a large area of southern South Dakota that is now in zone 5a, with typical winter season minimum temperatures in the -15 to -20 degrees Fahrenheit degree range. The USDA Plant Hardiness Zone Map website has a feature where you can search by ZIP code to find your local plant hardiness zone. Use the blue button below to visit their website and find your local zone.
Your local yard or garden may be warmer or colder than what the PHZ map shows, but it serves as a good starting point when selecting plants for your area. Your zone may have changed with the 2023 map updates, so we encourage caution in experimentation with adding new perennial plants into your garden. Remember that PHZ maps are just one tool for selecting the right plant for the right place. Soil type; microclimates; exposure to sunlight and wind; and fall, winter, and spring moisture and snow cover all play a role in the success of overwintering perennial plants. Additionally, South Dakota is known for large swings in temperature, which can be another consideration in selecting plants for our climate.
Using the map is quite simple. You hop onto the USDA plant hardiness website, punch in your zip code into the search bar, and you can see exactly what zone you are in. It should tell you the zone with the average low temps and give you the option to zoom in on the color-coded map for the general region related to the zip code. If you are located right on the threshold of multiple zones, my advice would be to err on the side of caution and go with the lower range of the two zones. If you need further info on how to use the maps, they can be found here.
What makes this even easier is that with this zone/temp information, when you are planning or shopping for plants, it's always something to reference. Almost all plants have an associated cold tolerance zone (sometimes called plant hardiness), and it's usually the USDA zone. However, please note, when researching online, make sure that it is referencing the USDA, as there are also other metric systems, like The Sunset Western Garden Zones, which are even more in-depth than just cold tolerance and used by more avid gardeners.
Beyond all the data and the fact that we have a new map to reference, why are we making a fuss about it? Well, in our minds, this is pretty concrete evidence that the climate is very much being affected by our actions, which in turn is having a negative impact on the planet. As our climate warms due to heat-trapping carbon pollution, planting zones have shifted north toward higher latitudes and elevations. Overall, the map shows data that it is, on average, 2.5 degrees warmer than previously.
Although some gardeners who have shifted from zone 7b to 8a might rejoice in that they can now try their gardening game at mandarins, kumquats, or maybe even a cold-hardy banana, the intense reality is that these shifts are also creating more space for invasive species, insects and pests to take hold and thrive in areas they previously couldn't. For example, gardeners in South Florida are struggling to grow tomato plants outdoors due to the extreme and extended heat scorching their plants and providing the perfect host for fungi to have negative effects on their plants.
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