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Anyone here feel that the 2012 Hardiness Map Released last year by the USDA has its drawbacks, or feel that the Zone representing your location is still not what the Map represents your area as? Do You feel that climate data updated through this year would make a measurable difference in your plant zone?
FWIW, there is a "Wikipedia" article on "hardiness zones" that discusses pros and cons of USDA climate zones that might make interesting reading. my understanding is that both Bandon, Oregon and Redding, California are nominally USDA 9b in the latest map. assuming I understand correctly, this would be a possible illustration of the defects of a hardiness zone based mainly on winter low temperatures (at least for parts of the western u.s.)---there is a significant difference in what can be grown in both places that simply looking at the map for corresponding zones doesn't show. though both places may have similar average lows the extreme high summer heat of interior Redding puts it in a different horticultural and climatic world compared to the very low heat accumulations of maritime Bandon. many of the plants that thrive in Bandon (many rhododendrons, fuchsias, hydrangeas, Monterey pine and Monterey cypress, for example) would literally burn up in Redding while a fair number of plants that thrive in Redding (most citrus, washingtonia palms, crepe myrtles) would be equally desolate on the coast. yes, there are a surprising number of plants that might do well in both places (agapanthus, bottle brush/callistemon, some eucalyptus, trachycarpus palms, coast redwoods for example). however, at least in this case, IMHO simply choosing plants for a "generic" zone 9 type climate would probably cause more problems than one might think.
Last edited by georgeinbandonoregon; 11-15-2013 at 10:09 PM..
Reason: correct spelling
I see your point there. One drawback of hardiness zones is that they don't tell you if a plant is likely to do well in a particular climate because they're just based on winter lows and don't take into account summer temperatures, humidity, rainfall, etc. But I never looked at them that way, I always looked at hardiness zones simply as an indication of whether or not a plant can survive the winter in a particular climate. I never looked at it as indication that the climate is well suited to a particular plant or that the plant is likely to thrive there.
FWIW, there is a "Wikipedia" article on "hardiness zones" that discusses pros and cons of USDA climate zones that might make interesting reading. my understanding is that both Bandon, Oregon and Redding, California are nominally USDA 9b in the latest map. assuming I understand correctly, this would be a possible illustration of the defects of a hardiness zone based mainly on winter low temperatures (at least for parts of the western u.s.)---there is a significant difference in what can be grown in both places that simply looking at the map for corresponding zones doesn't show. though both places may have similar average lows the extreme high summer heat of interior Redding puts it in a different horticultural and climatic world compared to the very low heat accumulations of maritime Bandon. many of the plants that thrive in Bandon (many rhododendrons, fuchsias, hydrangeas, Monterey pine and Monterey cypress, for example) would literally burn up in Redding while a fair number of plants that thrive in Redding (most citrus, washingtonia palms, crepe myrtles) would be equally desolate on the coast. yes, there are a surprising number of plants that might do well in both places (agapanthus, bottle brush/callistemon, some eucalyptus, trachycarpus palms, coast redwoods for example). however, at least in this case, IMHO simply choosing plants for a "generic" zone 9 type climate would probably cause more problems than one might think.
The wiki article covered a lot of the same territory I have been taken to task for by those who wish to be pretend experts based on their limited local experiences. The zone system is still valuable as a reference tool for cold survival of plants, which is often what "new to planting things" gardeners need. Your examples from within the same zone and state highlight just how variable conditions can be. It's hard to believe Corvallis and Bend are in the same state and not all that far apart (by miles as the crow flies) but have such a huge difference in what can be planted due to elevation and the effect of the mountain ranges on weather.
When someone has questions about how and where to plant something it is handy to have a starting point of where they are in the zones, but that is all it is; a starting point. If someone is in a zone "8" my first thought is NOT "well it does well for me in my zone 7 so therefore it will be perfect in their zone 8" because that is even warmer, but instead is: where on the continent is this zone 8? Is it coastal or continental, high elevation, desert or high rain? So many places get extremes of both heat and cold seasons, or hot days and cold nights, or cool winters and cool summers or some other combination that isn't understood by looking at the number of cold days at or below a certain temperature every winter. To add another wrinkle to that there are some plants that need a bigger difference between night and day temperatures, some that need a constant temperature and some that fail to thrive with fewer sunny days even if they are in the right temperatures.
My next question is what is the Heat Zone and what is the Sunset zone. These are not perfect either but all three combined will rule in or out certain plants and plant groups for making easy to care for gardens. Some plant descriptions and tags now include a double zone advice; one for the eastern half of the country and one for the west. Just about every "expert" who has been posting in this forum has handed out advice based simply on the USDA hardiness zone, or even just on the fact that where they live happens to be the most moderate of all places where everything is very easy to grow. That just reflects on the fact that all they know is a very local area and have limited understanding of how things grow elsewhere. I have seen several people encouraged to buy plants they shouldn't based on this limited knowledge. It doesn't matter if it is tulips or petunias, chrysanthemums or potatoes there are areas where you cannot grow certain plants, or need special varieties, because of factors other than cold hardiness.
All of the zones are based on climate conditions that are averages, there will be years where things are far colder or far warmer than those averages. If you plant a plant that is barely hardy to zone 8 but live in a current Zone 7b you may very well get away with it for a number of years until we have the winter with temps that go well below the average. Even within the zones there will be quite some variation based on elevation and terrain contours. Experienced gardeners begin to see a pattern of where they can plant things from a warmer zone and have it survive. This is where understanding how micro-climates form comes into play.
Zones are one part of the equation of plant survival in heat or cold. The amount of sunshine in each season, soil conditions, wind, humidity all take part in determining how well plants survive in each place. For those who live in transition zones like I do, where they have some things at their farthest northern reach and other plants stretched to the far southern reach this can be a tricky balance and it requires understanding all of the above and the risk of something not making it with every weather fluctuation. I don't blame the zones for failures though.
yes ,"eugeneonegin",think that's it. as you say, basically the USDA zones is all about if the plant survives the winter--after that, the plant is on it's own (the gardener, too) as to surviving whatever natural conditions are in play afterward (let alone whatever the gardener does or doesn't do in the way of good plant care in regards to feeding, watering, pest control, etc.). again, 2 areas may have "identical" USDA zones but significantly different climates. for example "zone 8" on the west coast will likely have wet, relatively cool winters but quite DRY and warmish summers while on the east coast the nominally same zone will have a possibility of rainfall thruout the year with generally hot, humid summers. the differing climates will very likely also have a different palate of plants that are adapted to those conditions---both native and introduced---that are really good for the garden. of course, some plants will be adaptable and do well in both zones with with reasonable care, others may need lots more help, and more than a few will not do well at all in one or the other zone---the cycle of heat, cold, moisture being too alien to their temperament. IMHO, no zone system is perfect but all can be useful to some degree in making initial ROUGH assessments of what plants MIGHT be better adapted to your climate.
"j&em", thanks for your comments and observations. Corvallis and Bend are a good example of how zones can function on the west coast where the USDA map zones show them going in a very different pattern than more easterly areas. in this case, Corvallis at low elevation and mostly maritime influenced has much milder (and wetter) winters than bend at a relatively high elevation on the east/windward side of a high mountain range with a colder more continental, much drier climate. Bend has more in common climatically and native vegetation wise with Flagstaff Arizona than Corvallis, iMHO the problem with any general forum is that you can get lots of "advice" and info from fairly knowledgable or at least well folks all over and some (or all of it) may not be useful to your climate in general and the microclimate of your garden in particular. IMHO (and as you also say), almost every book, system, or source of advice and information can only get you so far along in the process of researching, selecting, planting, and caring for the plants in your garden. in fact, there may be definite differences in your own yard between growing conditions on the north and east sides (cooler/shadier) and the south and west sides (hotter/sunnier) and that's just for starters as you probably already know. throw in the "transition zones" you speak of between geographically placed bands of roughly similar winter lows which kind of run north to south and patterns of weather systems often running somewhat west to east (but much more complicated than that, of course) and the prevailing local and regional topography (which may affect cold air drainage, sun and wind exposure) and that's just the start of the many different climate/weather influences you may have to deal with and especially in the transition areas "azonal" influences from weather fronts that may change the climate suddenly for the worse/colder unexpectedly for both plants and people. FWIW, as far as the SUNSET zones actually play out on the ground I'm most likely in the "transition zone" between their PNW coast zone 5 and the basically north California (and officially a bit of extreme southern Oregon) coast zone 17 able to grow a number of things that their "western garden book" does NOT recommend for zone 5 (huge Monterey cypress and Monterey pine for example) while not being completely long term successful with some recommended for zone 17 plants (canary island date palm and Tasmanian blue gum eucalyptus) so I have some sympathy for plants and people in "transition zones".
Last edited by georgeinbandonoregon; 11-16-2013 at 11:05 AM..
Reason: put more info in post
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