However it is done the Arbor folks revised the zone map that they use. In 2006 they released a new one. Do not know stats on USDA just on US Arboretum. Good to know USDA will update their map also.

The point here is the link. Folks who have trouble making sense out of any zone map can have a very easy way to get their growing zone. Who owns the map is not important. You simply type in your zipcode and click the button and your planting zone is immediately shown to you - not on a map but it will say "You are in zone --".

Let's not worry so much about the ownership of the map.
DL

This is not a matter of ownership (although if ownership doesn't matter, will you mind if some one else moves into your house or takes your car?).

It is matter that the Arbor Day Foundation used a seriously simplified methodology to create their map (and it is not an update. The Arbor Day Foundation has never had a map before). Their data selection would not pass muster with the scientists doing the newest edition of the USDA map. The Arbor Day Foundation methodology and choice of short data set led to a large number of zone changes that are not proving to be so in the new USDA map. According to the Arbor Day Foundation map, you can grow camellias in Boston. Sure, give that a try. Just don't spend a lot of money buying the camellias.

But, according to your message, it is better to easily understood and wrong then have to learn something to be right. I hope anyone who buys and plants something too tender for their actual zone based on your reply above sends you an email about it.

Why argue?

But to be clear, these are two different maps that may give you different zones when you enter your zip code. I'm in 7 on the Arbor Day one and a 6B on the USDA.

Here's a link where you can put your zip code in and get your USDA zone.

http://www.garden.org/zipzone/index.php

I play it safe myself and use my USDA zone. I think most books and catalogs use the USDA map.

No wonder these two different maps are causing confusion.

The Arbor Day site said my zipcode was zone 6-8 and the National Gardening site said 6b. I always thought I was
in zone 7. When is the new USDA map coming out Kimka?

It is in review as we speak. I can't give any kind of a firm deadline, but I will guarantee that I will post the link and announcement here the very first thing.

Arbor day said 7 - 8, and USDA said 6b. Christy :)

The zone maps are a great starting point, but regardless of what any map says, there may well be variations within any given zip code and it's up to the individual (gardener, in this case) to know his/her microclimate.

We happen to live on a slight hill that is surrounded on three sides by a bay, which tends to mitigage winter lows and summer highs. Add in the abundance of tall oaks with an understory of rhodies and mountain laurel, and you really get some summer cooling, as well as some resistance to winter winds. Can't count on it every year, but we've had things overwinter that, by the books, shouldn't in this zone. But if I drive a mile or so inland, it's a whole different story ... can be embarassing at times ... don't know how many times I'd run out to a local store on a quick errand comfortably attired for a spring day in jeans and sweatshirt, only to feel terribly out of place (and uncomfortably warm) among folks in shorts, sleeveless tops and sandals!

Hills, valleys, water, and where you are situated in relation to them, can make a surprising difference.

Even within your own property, if it's larger than an apartment balcony anyway, you can probably vary by one to one and a half zones.

We live on a quarter acre lot. The north and east sides are very windy and cold. The south side is sheltered from the wind, plus we have a walkout basement, so the plants up against the foundation wall get some heat coming through the wall, as well as sunlight absorbed into the cement wall.

We use this to our advantage - the north and east sides get the azaleas, hollies, and cold-loving evergreens. The south side gets the tropical plants, the borderline hardy stuff, and the pond.

agardenstateof_mind and watergal have hit on the single most important and often the most difficult point about hardiness zone maps. They are guides and even the new one USDA is working on still only goes to about 2 square kilometers at best (assuming there are weather reporting stations).Within zones there are micro climates and within your yard are mini-microcliimates (nanoclimates?).

Plus as I regularly tell reporters, the map is based on data from previous years (how many varies with whose map you are looking at). And you are asking it to predict the future behavior of weather. Thw weather guy on the TV news can't even accurately predict for next week. Just how specific do you think a map is going to be for next year.

Nothing will ever beat a gardener's knowledge of their own garden, as they see where cold pools and where they have a warm spot.

One of the best ways to discover your microclimates is to walk your property in the days after a snow. Look for warm areas, where the snow disappears fast, and cold areas, where it lingers for a long time.

dancinglemons-
The Arbor Day Foundation map worked for me. Where I am in MD it's hard to tell if I'm in 6b or 7a according to USDA and Arbor Day said I was 6-7 so that's close enough for me!