Did anyone see ...?

I just read a couple of threads about the weather and wondered if anyone saw the front page of the Washington Post yesterday? It says "Washington Warming to Southern Plants" and an accompanying illustration shows a revised zone map putting more of MD in zone 7. The new zone map was from the National Arbor Day Foundation. Article also quotes curator at U S Botanic Garden and Arbor Day Foundation spokesman about warming trend.

Here is link to Post article online:

http://www.washingtonpost.com/wp-dyn/content/article/2006/12/19/AR2006121901769.html

Would like to know what others think.

now I can stop trying futilely to remember if I'm 6a or 6b~~~~~~~~~~I can say 7

The Washington area was in zone 7 for years. The new zone maps (circa 1990) actually pushed some of the area into a colder zone 6. OH MY GOSH IT MUST MEAN THE ICE AGE IS COMING!!!!

Good old Washington Post.

I don't know why they feel the need to tinker with the hardiness zones every few years nor do I think you can take them as gospel. I really don't think a lot of those areas are comparable to, say, the Great Lakes areas far to the north, as far as climate goes. And really, how often have you seen the temperatures around here go down to minus 5 or 10? I don't ever remember it happening, not even here in the valley where it is a bit colder than in the metro area.

I remember some time in the early 1990's when it was 10 below zero a couple nights. That was in suburban Md. I remember because that was the first winter for the house we had built, had a big old party with people in and out the door all night, and the electric bill was through the roof. That's the only time I can think of.
The hardiness zones aren't meant to reflect similarities in climate, only temperature extremes. Zone 8 in Lincolnshire UK can't even think about growing some of the same plants as zone 8 Texans, because the rest of the year the weather is so different

I lived in Manassas until 1995 and it never got anywhere near below zero. We had one winter around that time it went down to about zero, but not below.

The maps are supposed to reflect averages temperatures and frost dates, not extremes.

My real point is you have to take the hardiness maps with a little grain of salt and you certainly can't take them as any kind of indication that the climate is changing. Unless you're the Washington Post.

Ya know, how else is the Arbor Day foundation gonna get anybody to notice them?

I don't know about Manasass, but it most certainly has gotten colder than zero at Dulles.
These are the average daily temperatures and record lows and highs for January at Dulles, since 1965. I guess I was remembering 1994. Remember Reagan's second inauguration, 1985, when it was too cold to have outdoors? It was 7 below zero at Dulles that day (probably at night)


http://www.erh.noaa.gov/lwx/climate/iad/Iadjan.txt

Quoted: "The maps are supposed to reflect averages temperatures and frost dates, not extremes."




The plant hardiness zone maps aren't supposed to reflect the average temperatures at all.

They show the average annual minimum temperature. There's a huge difference. The minimum only occurs once. That's why zone 8 in Texas can be above 100 degrees for three months, and zone 8 in England might not exceed 85 degrees at all. There are heat hardiness zone maps that show the average annual maximum temperature, too.

You're right, you can't take the maps as an indication that the weather is changing. It's the other way around....
When the climate changes, the maps change, reflecting the recorded data.

Seems like there's some confusion about plant hardiness zone maps (at least for me). I did an online search and Claypa is right- they show the average annual minimum temperature. Sure glad I got the map thing figured out.

(Claypa- I think I remember that really cold spell in the early 90's. My son was in 3rd or 4th grade and the schools were closed for a week or so. We couldn't even stay outside for very long. My house was full of little boys running around and jumping on everything!)

Now to add to the map confusion- I checked a book out of my library called "Heat-zone Gardening" and it has a heat-zone map. The map is divided into 12 zones which "are defined by average annual days above 86 degrees F".

What I'm trying to do is figure out what will grow here in Crofton but reading is no substitute for experience. I guess you just got to try to grow it.

Kat

memories! that really cold weekend ,my roomie and were driving to Wisp in her little tiny car, was touch and go after the Garrett County line! andtoo cold to ski the first day there.

Factor in microclimates,drainage, root competition and soil, so much comes down to trial and error. I'll gladly keep trying

Since when are average minimum temps not an average? I can't imagine over what period of years the average minimum temperature for this area would be minus 5 or 10.

The hardiness maps are useful to a point for planting - it doesn't make much sense to plant something here that would only survive a zone 8 minimum temp. But they're not terribly accurate and I certainly don't agree that they reflect climate change. I see climate as something that occurs over a much longer period of time than the 10 to 30 year life of these maps.

The average annual minimum temperature has been -5 to -10 for decades, except the last decade, which is why they changed the map.
Yes, the average annual average minimum temperature is an average, but there's a world of difference between that and the average temperature. It only takes one night at a certain temperature to cause damage to a tree or plant, which is why it's pointless to use average temperatures. They use the average of the extreme low temperatures.

You can't look at the average annual minimum temperature of say, minus 5, and think that an average cold temperature is minus 5.

All it means is you can reasonably expect temperatures to go below zero once that year. Then your peach trees are shot, or whatever, and it doesn't matter what the average temperature is. All that matters to the tree is it went below zero that one time

But see, that's my point. Even here in the valley, I've been here for 11 years, I've never had temperatures go that low and we're in an area that's usually colder than most of the rest of the valley. I lived in Manassas for 26 years last time around (and grew up there) and never knew the temperatures to go below zero.

So I don't know where they're getting their averages minimums from but they're certainly not from here. If they're getting their averages from Dulles, that's meaningless. Dulles weather can be quite different, in temperatures and in other weather issues such as rainfall, from here, from Manassas, even from Fairfax.

And I would expect parts of northern Virginia, as it has become more urban, to have warmer temperatures than in the past. Not because the climate throughout the region is changing but because buildings and blacktop hold the heat longer.

I used Dulles as an example because that's the first record that came up when I looked for DC weather records. I'll look for Manassas records. Most of the weather data is collected from airports, even little municipal airports. There's probably some near you.

If Northern Virginia can be expected to have warmer temperatures than in the past, the climate has changed and it doesn't matter what caused it.

Yes, I saw and read the Washington Post article, which I found to be very interesting. Front page news, none-the-less! It must have been a slooow news day!!

I've lived in suburban Maryland my whole life and can remember the temps dipping down into the single digits during the days, minus temps at night, plus factor in the wind chill and you know that 'Old Man Winter' had arrived! I do believe (if my memory serves me correctly) that we had a lot more snow during the 50's, 60's, '70's, & 80's (dating myself here). The school systems were shut down for a week or more (it doesn't take much!) and the whole area was paralized for quite some time. It reminded me of what Denver & surrounding Colorado areas are experiencing the past few days with their airports shut down and impassable road conditions.

The air and ground temps have definitely warmed up over the years. We've had a lot milder Winters in the past 10-20 years. Once every 5-6 years, we'll get a record snow fall, but it's not like we can expect these storms yearly or that they are hitting us one after another. I would take a record snow fall any time, rather than an ice storm! Talk about treacherous!!!

I've been seriously gardening in the past 10-15 yrs, since we moved to Ellicott City. I've been able to plant Musa bajoo & Datura, which come back every year! In the last year or two, I've been 'pushing' my growing zone 7a, or maybe it's now 7b, to see which warmer loving plants will tolerate our Winters.

An excellent example of our changing climate is to take a look at our Summers. We had terrible droughts, watering bans, & increased insect destruction for the past 3 years! Personally, I'm planting ONLY in the Fall, Winter (yes in December) & early Spring. I wouldn't plant ANYTHING in my garden from May through September! Why, because of the reasons listed above!! I can't tell you how many plants I've lost due to our terrible weather conditions in the Summer. It's like gardening in a very hot sauna!!

I have a hunch we're arguing because we're talking two different issues. I think climate change takes more than 10 or 20 years, but have no problem with anyone else seeing it differently.

I take more issue with the hardiness maps than I do the entire issue of global warming. I just think they're an extremely lousy method of trying to show climate change over any length of time, short or long, because I don't think they're all that accurate to begin with.

Shirley I remember all that snow we had when we were kids, especially in the 60s. I know one year we had to go to school on Saturdays for weeks because we'd missed so many snow days.

I just wanted to point out that it does go below zero occasionally in the Washington DC burbs.... not to argue. Or at least it used to. LOL! As far as I'm concerned, the climate change started with the Industrial Revolution, and we're now beginning to see the effects. I'm sure everyone wishes the maps were as accurate as possible, but even with more than 14,000 points of data collection, it will never be perfect.
I used to have to walk home from work late at night and remember my nose freezing, ducking my head into my coat so it wouldn't. I also wondered about the hardiness zone when I lived in Maine. I couldn't believe it went to 15 or 20 below zero, but eventually there were a few times when it did.

I couldn't find records for Manassas, but Warrenton and other places were all similar to the Dulles data.

Here's a link to the National Arboretum's hardiness zone map, if anyone's interested. There's a short blurb about how and why the 1990 version was revised from the 1965 version. No word on whether they're planning to change theirs.
It's a shame it's so hard to read; Better Homes and Gardens has a better site for the map, if you can stand all the pop-up ads. If you use a pop-up blocker, it almost sounds like popcorn cooking


http://www.usna.usda.gov/Hardzone/index.html