The zones are more or less a guideline for growing perennials, but It is not hard and fast. Yes you can have different microclimates in different parts of a zone.

Heck you can have microclimates in one yard. A plant rated for your zone may not survive in an open exposed area with no snow cover, while one rated for a zone warmer will in a protected area with snow cover.

All gardening is experamentation, so use the zone maps as a guide, but don't let it stop you from trying different plants.

i will make it as simple as i can .... and you will remember the simple explanation ... then gal will come and correct me.. and take it all to a higher level ...

climate is 100 variables.. heat.. cold.. humidity ... and you can dream up the other 97 ....

zone info.. in its simplest form.. is minimum winter cold ... and probably a bunch of other variables , but who cares ... lol ...

so your 5.. is my 5... and st loius 5 ... for winter min ...

but i have a conifer friend in st loius ... somewhere down there [kansas city???] .. who cant grow half the conifers i can up here due to summer heat and humidity ... go figure on that .... but we are both z5 ....

so when we take the zone info to a nursery to pick out stock.. all we are doing is selecting plants that can live through winter ....

as i said.. in its simplest form .... you can learn as much more about it as you want ....

the effect of lake MI is two fold ... the amount of snow that covers your garden [lake effect] .. and the extension of the growing season due to that big mass of water you are near .... if you drew a line directly east... to MI .... i would not be surprised if they are z6 .... prevailing winds make fall a bit longer since it takes the water longer to cool .... and the ice in spring makes their weather a bit different than yours ...

does the windy city wind blow to the lake.. or from the lake????

THEN.. we can fold in all the micro climate stuff.. like the effects of the cement jungle you live in/near, and how much heat it can retain .... etc ....

but... i THINK your prevailing wind pattern is like mine.. from the NW .... so in theory ... you are on the wrong side of lake MI for it to affect you as if you were on the other side ....

soooooooo ... if the zone maps tell you you are z5.. then yes you are .... but you MIGHT have a micro z6 ... but at that point you are going to complicate your gardening pleasure.. if you start zone pushing.. and buying plants that may or may not live over winter .... but that is another post .... micro's have a way of falling back to the lower zone every few years .....

ken

How close? If you're within a few blocks as I am (in my neighborhood, in the spring and summer especially, I can tell where major "lake effect" kicks in by how it gets cool when I cross what passes for ridges toward the lake), I think you can call it at 6. Or if you're in an urban enough area, you get the "heat island" effect too. I'm never sure just how far that inland Z6 might creep. I sort of watch the thermometer. In 10 years in my yard, it doesn't seem to have ever gotten below 0 according to my admittedly dodgy outdoor thermometer, and I grow a few things that are supposedly rated only to zone 6. But you never know what a winter will bring.

Zone maps vary, too, and it seems they get based on the last 15 years of climate readings, roughly. I was just looking at the 2006 Arbor Day Foundation one that confirms my Zone 6 leanings, and it's a little warmer than the 1990 USDA one, which only spots us lake-area dwellers to a 5b.

I do know, just from walking around, that my fall frosts come later, my winters are a wee bit milder, my summers generally cooler and my springs longer and colder (but with less risk of killing night frosts) than those living even a couple miles west. And that a winter cold snap without snow can still do some major harm.

thanks for the advice. I think the best thing I got from it is "select plants that can live through the winter" in my area--thanks, Ken. I'm a comparative beginner (started my garden 3 yrs. ago) and need advice. This forum is great for that. I've been lurking here for 2 weeks and love it. Miriam

One thing to remember is that zone ratings are based on the average winter minimum temperature.

A lot of times people will say "Well, I can't be in zone 6 because it got down to 25 below a few years ago." But that's not the way it works. There will always be outlier years where the winter minimum is colder or warmer than average.

Most times plants can take the extra cold, but even if not, that shouldn't stop you from trying perennials that are borderline hardy in your area. They may do just fine for many years, especially if grown in a somewhat protected location and in well-drained soil.

I'm supposed to be in zone 6 according to the USDA map. Not even close :)

My lowest temperatuer is ofter -27 F. and my frost times are from end of May/first of June to first of September, sometimes a week or two later, but you can't count on that.

I just stick with zone 4 and figure anything warmer is going to have to be protected and pretty tough. I think the -27 F. was in my microclimate, since the thermometer is on the front porch and we seem to lose a lot of heat around the windows and front door. I don't know how cold it is in the back pasture by the creek!

I'm in a pocket of Zone 6 in South-East Michigan (though I live north of Windsor, Ontario, Canada). In the past few years I have seen lows of 6,6,4,3,-2F. In my front yard I have a clump of calla lilies (which I've had for the past 3 years and have gotten blooms each summer). My mother-in-law lives 4 miles west of me and her lows are usually 3-5 degrees colder than mine (I'm within 1/3rd of a mile from a very large lake).

Given the mathematics which compute averages, I could easily have a low temperature of -17 degrees this year and my average over the last 6 years would still only be 0 (zero), but I would likely lose many of the plants I get to brag about growing outdoors in Michigan if such a low were reached for any length of time. (passion flowers, poncirus (citrus relative) fig, etc)

btw...wind-chill counts for nothing with regard to plants, though cold winds can dessicate tender plants (it however doesn't have to be that cold for dessication, though).

~Chills

well, from everything I''ve read here I conclude that zone designations are very
vague and/or misleading. I think I'm in zone 5 sometimes and zone 6 other times. Maybe zone 4, too, some parts of the growing year. Miriam

Not misleading... just a guideline (as one of the first responses indicated). They will give you a good idea as to which plants will likely survive the winter where you live. Add to that some variables that are unique/specific to your location/situation and you might go up or down one zone.

Again, think "general guideline"... and otherwise, have fun and learn.

Here's to dirt under your nails... at least next spring. ;)

coolplantsguy: I've already learned more on this forum (in 2 weeks) than I knew when I started out last summer.
Miriam

I live half way between O'Hare airport and the lake. In winter, the temperature in my neighborhood is always warmer than what is reported at O'Hare. It is even warmer downtown which is on the lake. In Chicago itself, the temperature has not dropped anywhere near -20F in more than 20 years, so I have been experimenting with zone 6 plants in my garden. :-D

I know though that in the west suburbs, it can drop way below -20F. So those gardens are definitely in zone 5.