let use MY z5 ....

i can grow anything with a lower number.... and it will survive winter ...

i MIGHT be able to zone push a z6 in a perfect micro climate ...

i can grow anything above 6 ... e.g. 7 .... as annuals ... and many such are called annuals up here ...

in theory ... with no other variables.. you should be able to grow anything with a number lower than yours... but that is leaving out a lot of other variables ...

when it all boils down ... zone is MIN WINTER TEMP.... for a plant to survive winter ... and it really doesnt tell you much else about anything ...

one might suggest ... in your z 10-11 .... you dont know what winter is.. lol ... e.g. it was 4 below when i got up Thurs morn ... i had to put on my windbreaker to go outside... lol ...

ken

ps: with questions... the search for knowledge... the only stupid question.. is the UNASKED question ... we all come here.. because we like to teach and share... have no fear ....

The USDA Plant hardiness Zones are a guide to which plants will survive a normal winter in those areas. So plants designated as zone 10-11 should be okay outside in a winter when temperatures do not fall below about 30 degrees F. Gardeners in colder zones might try growing such a plant if they have a sheltered area, a micro climate, but someone in zone 5 would need to grow this plant in a container so it could be moved into a much warmer environment, ie. the Lantana we had for 25 years here.

Cheryl, another thing to consider is that many, many of our favorite flowering seasonal plants may be described for the very warm zones, but are commonly grown AS annuals anywhere.

There are some perennials used as summer annuals in cooler climates, but winter annuals where it's much warmer year round.

Honestly, most of the plants discussed in the Annuals Forum are actually tender perennials, so available and inexpensive that they are easy to dispose of at the end of the season.

So, it always makes good sense to ask about the plants that you might be interested in.

cakbu, and "global warming" appears to be a factor of change.
I read that one effect of "global warming" is that it might be pushing the boundaries of the zones gradually northward; and plants may flourish in areas where they customarily do not.
My personal observation has been that 30 years ago, I had to travel at least 50 miles south of where I live to see flowers on the umbrella tree Schefflera actinophylla. Nowadays, I see many in the county where I live.
LINK.

According to the people at NOAA and the USDA I am now in USDA PHZ 6, but my temperature records do not support their data. Some of us have long known that there are micro climates and that because of the amount of concrete, masonry, heat retaining structures in cities they can be a zone, or even two, warmer then the surrounding country side.

"When a plant is noted to be appropriate for a zone(s), say 10-11, does that mean ONLY those two zones? Or any zone below that range up to 10-11? Or conversely, starting at those zones and going higher. "

The answer to this, as with almost any other question, is "It depends."

There are many 10-11 zone plants that can be grown in cooler climates if they are protected from frosts. And many plants from 5-6 zones can live happily in the very warm climates. But not all.

Besides specific temperature ranges some plants often have humidity requirements- for example many of the warm weather plants grown in southern California or the Southwest do terribly in South Florida (poppies) because it is simply too humid for them. And it works the other way as well- many plants like orchids need the humidity and don't fare well in more arid regions no matter how warm it stays.

Also, some plants have cold weather requirements- they actually need xx number of days at low temperatures in order to set blooms like blueberries, or a period of dormancy within their life cycle like deciduous trees.

Every climate has it's own peculiarities- as novice gardeners I think one should stick to tried and true but as experience increases so will the desire to push boundaries of zone. Sometimes you have massive success and other times fail miserably.
Then we learn about micro-climates and set about creating little niches in our gardens to feature a much wanted species that has particular needs. It all depends on how much time you want to invest in caring for a plant. If someone in a very warm, arid climate is determined to grow Vandas outdoors they can build a water feature in such a manner as to increase the humidity in one small zone.
Some people like the tropical palm enthusiasts in cold climates build enormous structures every winter to heat the plant and keep it surviving through each winter while other folks are more of an every plant for itself mentality.

Gardening is easy if you follow a few simple rules- find out what a plant needs and give it to them. If you think you can do that go for it. If you think it is beyond you, maybe skip it.

When I lived in South Florida all my temperate friends envied my ability to use anthuriums and bromeliads and the like as landscape plants. And I dreamed of being able to have Japanese Maples and hydrangeas and other more temperate species.
I think we always want what we can't have and tend to push boundaries to get it. And that's OK.
But do your research before you step too far out of the box. If it is a plant that you never see in your area there's probably a good reason for it.

cakbu, "When I lived in South Florida all my temperate friends....." wrote cearbhaill.
Does he have intemperate friends?
On second thoughts, I withdraw the question.