Hardy to Zone Question?

Head hung low, I feel rather different to ask a question. I have been seeing in databases mentioning plants "hardy to zone 6", and so on. I wonder what this means. Does the plant survive in zones 1 to 6 or the other way up from 11?

Dinu - Chin up ! The zones run from 12-1. 12 is hottest, 1 is coldest. And they are pretty consistent all around the globe.

In addition to Honeygirl's explanation, the zones are simply average minimum winter temperature, they don't take into account climate. A plant might be hardy to zone 6 (- 5F or -20.5C) but it doesn't mean it will thrive in some zone 8s due to climate difference.

Before I came here zones meant nothing to me, they still don't from a gardening stand point because our winters tend to be mild, it's the spring and autumn weather that kills a lot of our more tender plants so you're not alone!

If it says hardy to zone 6 that means it should survive zone 6 winters, but not colder. So you could say that means 6 and up (zones 6 - 12) but it only takes into account the cold hardiness of the plant. Lots of stuff can't take heat, or humidity, or it needs a cold spell .... none of that is reflected in the hardiness zones.

Cheri'

As discussed above, it means that it is hardy in zone 6 and warmer. In most of the U.S., winter cold is the limiting growing factor, so that is what most people concern themselves with. Where you live and where I live, summer heat and dryness and lack of winter cold tend to be the more important limiting factors. But I have lived in zone 5, so I know where cold-winter people are coming from, too.

Dinu's question points out the main reason it's not enough to simply check off one box in the PDB: users need to know that a plant is hardy within a specific range: Zones 6 thru 9, for example.

If only zone 6 is checked, two things happen that shouldn't:

1) if you use the Advanced Search to find a plant hardy to zone 7, a plant marked as simply "zone 6" won't come up in the results. (The system can't intuitively "know" which plants to select for search results: the checkboxes are what "tell" the system which plants to select.)

2) Assuming the reader finds the plant entry by another means, they are still left to wonder if "zone 6" means it's hardy from zones 2-6 or zones 6-11, as Dinu did.

Dinu, that confused me for years too.

I live in the Southeastern portion of the United States, where summers are hot and humid and winters are mild. I tend to notice whether plants can survive the heat, rather than harsh winter conditions.

There are SO many plants that I would like to grow, but I know that the summer sun, here, would fry them, or that the humid conditions would rot them. Or both! :D

I also wondered about whether the zone factor included areas up or down from that listed.

You have seen the cold-hardiness maps. If heat is a factor in your area, here is a heat-zone map (of the U.S.). There might be similar maps for your area also.

http://members.aol.com/Jyex2/map_heat_zone.gif

I got this map from the American Horticultural Society, and you can read how it is used on their explanatory page:

http://www.ahs.org/publications/heat_zone_map.htm

Hope that helps a little.

Jean

Thanks friends. That did clarify my doubt to some extent. In books written by Indian authors they mention two different things - 'hills and plains'. Mysore is in the plains. People have tried to bring plants from the hills (where the climate is a lot cooler and never gets hot) and they naturally have failed, even though the hills are within a 100mile range. For example some ahthuriums and calla lillies are grown in the hills. They never survive when it is brought to the plains (where it is warmer). It is somewhat true the other way round too.

So when I read in databases about plants "hardy to zone 9" would mean from zone 12 up to 9? ".. to zone 5" would mean somewhere between zone 8 up to 5? Should we add about 2-3 zones on either side to get its probable range?

Dinu

It's best to research the plants hardiness further if the information isn't immediately available, some plants are very sensitive to temperature without cover. Saves on a lot of dead plants.

Here in the UK we use the terms hardy, half hardy and tender and like yourself there are some plants that do well in the hills and uplands that won't grow well here in the lowlands and downs regions

That means you have only 3 broad group-classifications. Is that the reason why some seeds I get from lower?cooler zones never sprout?

Yes we do but then again we're insignificant in land mass. Our climates do vary in heat and a small amount in seasons but the lowest temperatures don't have a large range here.

If you're growing plants from a cooler zone, you might do well to place them in the coolest area you can find for about 4 weeks. I don't like germinating seeds in the fridge, we have a larder that serves just as well

Dinu wrote:

"So when I read in databases about plants "hardy to zone 9" would mean from zone 12 up to 9? ".. to zone 5" would mean somewhere between zone 8 up to 5? Should we add about 2-3 zones on either side to get its probable range?"

I am still confused about this too.

I see so many plants listed as "Hardy to Zone 8" and I assume that they will not grow well here in Zone 9. Am I assuming correctly?

Jean

This is one of the problems with using the USDA zones. All the USDA zone indicates is the average minimum winter temperature of a given area.

Louisiana Sweetpea, you and I are technically in the same USDA zone and yet out climates are different. Plants that will do well in my garden would probably faint in your summer heat, plants that grow well for you in your climate would probably hate our long coolish springs and refuse to flower or seed here as our summer temperatures here in S. England are around 70-80F on average. Our season lengths are different too, we have long springs and autumns, with short summers and winters.

IMHO I'd rather see a different listing for hardiness created which includes the gamut of climates but that will be a long time in the future!

LouisianaSweetPea,

I see so many plants listed as "Hardy to Zone 8" and I assume that they will not grow well here in Zone 9. Am I assuming correctly?

In theory, when the plant says "Hardy to Zone 8", it is also hardy in Zone 9 because they are talking about the cold hardiness. Which means that the plant, if hardy to Zone 8, will die if exposed to temps colder than Zone 8 (zones 1-7). However, like people stated above, you still don't have a guarantee that it will survive the heat, humidity, drought, extreme wetness... or sun or shade for that matter.



This message was edited May 19, 2004 11:17 AM

When I see "hardy to zone 8", to me that means it will survive winters down to as cold as they get in zone 8. That is, it will survive down to 10F degrees. (By definition, zone 8 is unlikely to get winter temps below 10 degrees.) How this plant handles heat is a whole other animal and this is not covered by USDA zone numbers, as others have discussed already. "Sunset" zones, which I have talked about in another thread, attempt to take into consideration heat, cold, and humidity (or lack thereof), but Sunset zones don't seem to have ever caught on east of the Rockies.

I used to know my sunset zone, but never ever ever find it useful, because no one (outside of California maybe) uses it. =( It would be wonderful if people did.

OTOH, I'd be thrilled if I could get a heat zone rating on many plants. But I get excited if I find info that differentiates between zone 9 South (9s) and zone 9 West (9w). Moist heat Vs. Dry heat . . . it's a whole different thing.

Not gonna happen, apparently, so it's trial and error.

On that note - I have a favor to ask of everyone here who is in the US. Please go to the PDB and enter 5 zip code reports. It's unbelievable how helpful those are . . .

Cheri'

I agree that the USDA zones don't do a whole lot of good. Me being in USDA zone 7b (or 8a according to the new map), does not say much if you don't add that I am in Heat Zone 9.

I also agree with the Sunset zones being more exact, but isn't it copyrighted by Sunset? I think that is a big reason it is not used by many people or companies. I don't believe they can include the map for reference.