-I am recently searching for the ideal temperature range for my plants, and i must admit i have confused a little..
what i mean is that just very recently i discovered that when i read about plant's temperature hardiness or hardiness zones , in fact i am reading the average minimum tolerance temperature!...is it so? .
so , what about the maximum temperature a plant can tolerate?...where and how can i inform about it?
Living in Texas, USA, I would think that all plants have some "preferred" temperature range as well as preferred moisture content of the soil, fertilization levels, light levels, etc., but I don't think I've ever encountered a plant that died when some theoretical high temperature was reached, that is, barring some level past say... 105-115°F. At most, I've seen plants go dormant or nearly dormant when temps rise to some level but they didn't die, they just "rested" (top stops growing and may turn brownish but roots remain actively and viable) until the temps got down to a level that was more to the plant's growth requirements and tolerance levels.
You are correct in that the Hardiness Zone Maps typically indicate the average low temperature that one will experience in your immediate area, "average" being the key word here. This is tempered however by the existence of small areas/pockets that may be sheltered from extreme winter conditions, more or less rainfall, and other conditions like a brick/stone wall that holds or absorbs heat at a rate much higher than other areas even in close proximity.
First time I've ever seen the "heat question" so my answer may not be of much help to you but in general, it's not something you should worry about unless you're trying to grow specialty plants.
it all depends on the type of plants you are looking to grow, there is no point trying to grow plants that inhabit the rocky mountain paths of Switzerland in a hot environment like you have in Greece.
Most plants you purchase either from store or as packets of seeds will give you guidance as to the temps required for good plant growth and most adult healthy plants will tolerate a few days below or above the said temps recommended as long as you can offer some extra water in the hotter temps and shelter from lower temps IF you see the plants become distressed.
Does this help you in any way, if not, give a list of plants you are hoping to grow and see if anyone else can help you out.
Best of luck.
well , first of all thanks so much for all replies ...very kind of you!
secondly , i didnt knew whatever TXSkeeter wrote about the behaviour of plants at extreme high temperatures... I havent noticed so , as i am a beginner gardener and i have no experience...I suppose the same happens with the opposite..i mean with extreme low temperatures...let's mention a plant for example..is it cyclamen such a case? ...as it dissapears in summer months and return back in Autumn?...another question now comes into my mind...how we know when a plant is annual or just dormant? ...of course we can read it before we plant it , but is there any way to know it , and just wait to return?
-Now to answer to WeeNel , there are some plants that i use to keep into my balcony , most of them are Tropical plants i think , and i have not enough room to move them inside my house...that's why i am asking so ..for example i am not sure if i can move into my balcony , a sansevieria , or some succulents , or a shefflera ...i can name them one by one if you want...
also , i keep many plants in a cottage i have , where weather conditions are about the same as my main house , but i really worry about them also...i can name them also , if you are interested
..finally something more ...i have discovered into web and read about AHS which is a chart with areas with the maximum of days over 30 degrees of Celcium , but i suppose there are also many other factors for healthy plants...anyway i think it helps also to have an idea , as i found the AHS for my area
Thanks vTr...by the way Athens that is my area , is USDA: 9b (although i think it is more ) and AHS: 7 (again i think i disagree) according to informations from web..
If the winter cold is pretty much like USDA zone 9b, then you will need to protect or move indoors the plants you list. I am in 9b and have seen winter damage to most of those.
Sanseveria- move it in.
Schefflera- protect or move it in. I have one (Hawaiian Elf) under a plastic roof and semi-open walls. Cold wind can blow through but never frost in there.
Some succulents are fine outdoors, in a container, others need protection. Without names, no way to be specific.
Going by those charts you can probably pick out plants that are safe to grow, but not all plants are at their best in a zone, even if they are listed for it.
One way to tell if a plant is annual (and dead) vs perennial (and dormant) is if the plant is a bulb. Cyclamen, and many other plants grow from some sort of swollen root or stem part, commonly called a bulb, though the botanical terms vary. If there is something fleshy under the ground, and it has no leaves, it could well be a dormant bulb, and will come back.
Many perennials do not have a bulb, but have more of a stringy root mass, and you might find some dormant buds among the roots.
Best way to tell is to read the literature. Then, if you have a plant that goes dormant, looses all its top growth, then you should mark the location (even if it is in a pot) so you remember not to dig it up. That way you are not doing damage to the bulb, not mistaking the diffuse root mass for an empty pot.
Don't know if this is what you read, and I don't have a link for the following (I'm really helpful, eh?) but there is a chart for Heat Hardiness. I've only seen it referenced in the last few years.
As others have said, all of the charts, etc. are kinda general guidelines. Once your plants get a few years growth on them, they might adapt better to your climate. As a relative beginner in my current zone, I know that a few years can seem like forever. Be patient. You might lose a plant or two, but you'll eventually get the hang of it. And then you'll be so glad that you became a gardener.
I agree with tx_flower_child, most plants mature into their growing environment after 2-3 years of coaxing and TLC, so therefore the most worrying time is for that first period, however that cant mean you can plant a Canna in the ground and expect it to survive being covered with ground freeze when you know they require a much warmer climate, BUT with care like Mulch, fleece wrap around shrubs in the coldest temps and leaf mould added in thick layers, then there's every chance they will return for the next years display, maybe a few weeks later than normal but worth a try.
Good luck and best regards.
-Firstly Thanks so much everyone for your replies!
but ...still have a couple questions...and i will explain with an example ...at least i will try ( my english arent perfect...sorry)
-Let's take for example a plant ... Gardenia jasminoides..
well...this plant has hardiness zones (USDA) 8-10 which means a temperature range from -12,2 degrees to 4,4 degrees of celcium!...so , is that means that this plant has tolerange temperature -12,2 degr. Celcium??? and also why 8-10 and not 8-12? or 8 and above?...do you understand what i want to mean?...as my english arent so perfect...sorry
..also reading that this plant , Gardenia has a temp. range 15-24 at which it thrives...so what range is that , since as i wrote before it can tolerate ...-12,2 Celcium?...is that range , an IDEAL temperature range at which this plant thrives and bloom?
You are right that if a plant is suggested for nothing warmer than zone 10 it probably is not going to do as well in the warmer zones.
But there are ways to get around this.
I will use Gardenia augusta (old name is G. jasminoides) as an example:
Most of the neighborhoods around me (where I do landscape design) are zone 9b.
But this can vary quite a bit. Included in this 9b area are neighborhoods where the summer temps regularly hit 38*C, though most of the time temps a few degrees lower are typical (about 30*C). Winter cold is into the freezing temps, but only by a few degrees. (Rarely colder than -5*C)
In those cities I have seen Gardenia augusta (probably variety Veitchii) against a south facing wall surrounded by concrete. Thriving, full of blooms. Strong, healthy, deep green leaves.
At the other extreme there are some cities still in zone 9b but summer temps are often 10*C cooler, often seeing 26*C, but rarely higher. In these cities I have seen G. augusta (Mystery, Veitchii, others) in part shade settings (such as under high, fairly open trees) and they look too sparse, easily not getting enough sun.
My own G. a. 'Mystery' is slower growing because I do not use much water, and it is in bloom right now (October). It is in a fairly sunny location, but not full sun all day. Late afternoon shade. I am in one of those slightly milder parts of 9b.
So, if a plant is listed for a zone that is significantly colder in the winter than your zone, it might be that the plant demands some winter chill, a certain number of days below freezing. Probably not going to work in your area.
If a plant is listed for a zone that is significantly warmer than your zone in the winter, it is probably because the plant cannot handle the frost. These plants are worth trying if you can provide some winter protection. Plant them in an area that is warmer in the winter, protected from chilling winds, perhaps put a sheet of clear plastic over them, or put a string of Christmas lights around them.
If a plant is listed for warmer zones when you are comparing summer temperatures it might be that the plant needs some heat for example to ripen some fruit, or to set flower buds. Grow these plants in the most heat you can find. Against a south facing wall, and so on.
That is the way that Gardenia works in the milder 9b cities near me. To me, it is known as a plant that thrives in the heat. But your summer temperatures might be even too much, so try it in some afternoon shade. Perhaps under a high tree so there is good light, just not full hot sun, especially reflected off a wall. Try to find something else for those hottest exposures.
From what you've said about your alleged zones, depending on the type of light (direct or indirect) & temp (hot but not too hot or cold but not too cold, says Goldilocks), I would think that sansevieria aka mother-in-law's tongue, shefflera, and most succulents could live on a balcony. (Won't comment on Gardenia as I've never grown one but I am going to get some tiny ones in a trade later this month. Woo hoo.) Having said that, they do not like cold weather. Especially schefflera. So without trying c to f conversions, I think you're on the right track.
Can't remember if this has been mentioned w/o reading all the way back thru this thread, but one thing to help raise a plant's temp a wee (oops, no pun, WeeNei) bit before a frost is to give it a good watering. Forgot why this helps but it does.
Your English is just fine. My grammar 's not so good (note the run-on sentences) but that's more for my own amusement and trying to write the way I talk. Oh, maybe that's not a good excuse.
Anyway, you're going to do just fine. And Dave's Garden is a great place to use for reference, even if we all may disagree a bit from time to time. :D
Hope it all works out and so glad there is, some times agreement, but you know what D, Id rather watch a plant grow well than win an argument, let's be honest, gardening is for most, a calming hobby so arguments become personal in most cases and gardeners should throw them out into the compost like all the other kitchen crap LOL.
Take good care and enjoy your plants.
When you see a range for hardiness it usually means that it won't survive the lowest temperatures in a lower numbered Zone(USDA). It also means that in a higher numbered zone than the range list there isn't enough cold weather to force it to go dormant or produce flowers or whatever it needs to do in it's native habitat.
For example daffodils need a certain number of hours when it is cool so that they know spring has come and it's time to grow again.
I have just compared some climate charts of Athens, Greece to my local climate. It is so close to the same, that I would feel quite comfortable saying you could use the USDA zone 9b as a really close target.