I often have been confused with this term hardy. I am mostly interested in cold hardiness of tropical and subtropical plants grown in marginal climates. Does the term relate to survival of the plant, no visible damage or something else? I know that hardiness can vary depending on the climate, weather and other factors leading up to the event a plant is exposed to cold. Are there any guidelines or does this vary a lot?
hardiness refers to a plants ability to thrive and/or survive in a given temperature zone. for example, roses grow very well in my zone 6. there are some varieties that don't do well in hotter areas like zone 9 - although they may still survive, they may not thrive (as in produce blooms). and then there's the other side, colder areas like a zone 3 - some varieties may not survive the cold winters although they may do fairly well during the warmer summer months. most plants sold in stores have a 'hardiness range' listed telling you the highest and lowest zones the plant will grow in...let's say, for purposes of this example, the range is 4-7. the plant will grow in any/all of those zones. in zone 4 and zone 7, it would be chancy as to just how well the plant will do - being at the edge of the range, the plant will be more susceptible to extremes in temps that may occur in those zones (whether it's too high or too low). although it will still grow and survive, it most probably won't ever be the best it can be (thrive). the plant will generally thrive (as in do extremely well) in zones 5 and 6 since the extremes in the temps will be less likely to occur. due to this, the usda zone map (if you look at the newer version of it) actually splits the individual zones into two additional zones. if you note my info, i'm in zone 6b...still the basic 6 rating...on the warmer side though. so, i could, conceivably grow something that is rated at zone 7 and it may very well survive and even thrive. case in point, gladiola corms are supposed to be dug up before winter hits in zone 6. i've never done that and they have come back every year...i do mulch them for the winter, so that's part of it. there's also the 'microclimate' in my yard...the spot i planted them is a bit protected from strong winds (which can be extremely cold in winter) and it's also very sunny - which makes a difference in the winter. so, they do well here...not just survive, they actually thrive. so, if you like something and you live somewhere where it's just one zone rating off, it's worth trying to grow it...you will just need to do a little compensating for it and provide a bit of a protected spot to offset the conditions. if it's too hot, put the plant in a spot that is shaded during the hottest part of the day (afternoon to late afternoon) and make sure you provide enough moisture to compensate for the excess heat and, if you're in an area that's too cold, put it in a spot that is protected from the damaging cold winds in winter and make sure it gets sufficient sunlight so that it's warmed by the sun's rays.
Definition varies with source. Some may be talking about point at which top freezes off but is likely to grow back from roots, others how cold it can get before the plant is damaged. But the dominant tendency seems to be to indicate where damage begins, particularly when specific temperatures are given. When zones are listed often these are by commercial sources who of course have a tendency to represent as broad a range of parameters as possible, so as to appeal to as large a market as possible. Another occurrence is misunderstanding of what the USDA zones refer to (average annual minimum temperature ranges, and not lowest temperatures experienced in each zone); some publications may also have their own zoning system based on the USDA one but not exactly the same - you should always check for their own explanations of such terms if you wish to be clear on what exactly each designation refers to.
To muddy the waters even further, some plants, even in the same genus and speices can vary in hardiness. Text book answers are only a guide line as I'm sure everyone who's gardened for a while can attest. Cheers, LPN.
Depends on how well-written the books consulted are. Some think that in a book automatically = unreliable or fanciful. The same parties may consider something blurted out on the internet the true facts. At least books are usually edited for content.
Thanks for the help. I was just wondering if I was missing out on some guide that others were following. Some things that I have read don't make much sence and can be quite misleading. I have learned the hard way since I am in a cold microclimate for my area.
Sunset climate zones works well for California, Arizona etc where there is serious detail. Us in the PNW coastal areas have very little detail. If memory serves me, any of the British Columbia entries are pathetic or at best very generalized. I guess the info published is as good as the info they get (or seek). Cheers, LPN.
I am familiar with the Sunset Western Garden Book and the climate zones. They seem to be a bit off for my area. The lowest I have seen here is below the 20 year low, and possibly lower than the altime low.
