Term that has been used is modified Medit. Same concentration of precipitation in winter, but with lower temperatures in winter and summer. For local garden climate (as opposed to hardiness zone only) mapping and descriptions see Sunset Western Garden Book. Briefer climate profiles and less developed (than in the book) maps are also available on Sunset Publications web site.

You are in the path of cold winds coming down the Fraser River during winter plus much of the gardening and living environment up there is exposed due to the presence of prairies and clearing for agriculture.

Later I saw in WSU Master Gardener magazine that a cutting edge company in Oregon has been engaged to prepare the next USDA hardiness zone map. They are using a much broader range of data sources, with coverage down to the half mile level! Will probably be based on 30 years of readings, rather than the 13 the last one was. Sounds like the new map will be pretty slick.

As far as practical application to growing plants in our climate, 'Mediterranean climate' falls short, but so does the more traditional idea that we are in a maritime climate. Most true maritime climates of the world (for example, Britain, from which much plant data from our region has been gleamed, or southern New Zealand), experience significant precipitation in the summer - often it is spread evenly throughout the year - and less summer heat than the Pacific Northwest. On the other hand, true Mediterranean climates of the world are mild enough in winter for winter to be the active growth period for many plants that go dormant in the summer. That could be said about few plants or locales in the Pacific Northwest north of the south Oregon Coast. Most of the region is too cold in winter - in terms of averages - for plants to grow in winter and have a summer dormant period.

So we have our own unique climate with some characteristics of both maritime and Mediterranean climates. Many true Mediterranean plants, and plants from regions of the world with a similar climate, adapt well here and make their period of active growth in the spring instead of winter. Others are simply too cold tender for us, though they may thrive through a series of consecutive mild winters. Others would be happy here but they can't quite get the heat they need to thrive. Some plants native to true maritime climates adapt well here, enduring our dry summers. Others find our climate to be too hot, dry, or cold; or some combination of those factors, to perform well.

The neighbors may not know exactly why their plants grow, but you can always spy on their plants themselves. Microclimates created by slope and masonry can affect growth quite a bit. Some brave souls grow "California" plants like persimmons here in Portland, but they're cultivated with great care in sheltered spots with wind protection and southern sunlight.

Cuttings or seeds from a locally-successful examples can be a better bet than catalog plants.

If you've been here a year or two, you're probably already starting to observe things like wind direction, seasonal weather patterns, and soil qualities. It takes time to regain the knowledge you lose by moving; there's no substitute for local experience. On the other hand, you may notice things about your local environment that your neighbors overlook. And have access to seeds from distant friends that may flourish against all expectations in your new home, with your expert help.

Good luck.

Here is a link that might be useful: Do It Yourself intro to Microclimates

The two main persimmons grown for fruit here are both hardy trees planted in the open. Neither have been especially hard to find at garden centers in the recent past, although the Asian species would be expected to be the one consistently offered. Summers in Portland are hot enough for American persimmon to ripen fruit in ordinary sunny sites, up here in western WA it tends to grow slowly (and ripen some fruits only, and maybe not every year). Nevertheless, Seattle has specimens over 40' tall. Locally suitable cultivars of Kaki persimmon can be harvested annually. A street in Seattle has this over 35' tall.

I've been told that an average Mediterranean climate is drier in the winter than we have here, is that true? It seems like many Mediterranean-type plants seem to survive a little better here when they have maximum drainage in winter.
- Tom

You could say that's true although you have to do a lot of averaging to say it. An 'average' Mediterranean climate might get about 15-30 (40 in some places) inches of annual precipitation. Around here, north of, say Eugene (and excluding the Olympic Rainshadow) we mostly get about 30-60 inches annually (more in some places). Our poster from the San Juan Islands, however, probably receives under 30 inches.

Regardless of precipitation amounts, I think your observations concerning plant performance are correct. Drainage and precipitation do partially determine success with Mediterranean-type plants here, and are crucial for some of them, though they are not the only factors - the other two obvious ones being summer heat (they often want more) and frost (it's too cold here for some plants).

Thanks Ian. Does anyone know which city(s) might be said to exemplify a "Mediterranean climate"? Rome maybe?

I think all of the Mediterranean, the west coast of the US (and southern BC), southeastern coast of Australia, coastal parts of South Africa, New Zealand and Chile.

Certainly Rome and anywhere in the Mediterranean region.... Barcelona, Naples, Jerusalem. In other parts of the world.... Perth, Australia; Cape Town, South Africa; Santiago, Chile; and Santa Barbera, California would be more examples. I don't think anywhere in New Zealand or the east coast of Australia has the right precipitation pattern to fit the bill... too wet in summer.

So I found some interesting comparisons on weather by month, link below. It looks like Seattle has about 159% of the January rain in Rome, and Olympia has 228% of of Rome's Jan. rain. There is even more difference at Barcelona. That makes a huge difference in horticulture, especialy with the few degrees colder we average (even more difference on record low temps).
So I wonder if perhaps our Mediterranean-like climate might be very restricted to just some small island areas and that little patch at Sequim?

Here is a link that might be useful: Seattle to Rome comparison

Interesting web page. It occurs to me that just comparing January to January doesn't give you the whole picture. The sites I'm looking at in the Mediterranean region are wetter in fall, drier in winter and about the same in spring when compared to Seattle. The some total of which is.... about the same rainfall as our region or a little less, but with an earlier summer dry period.

On the other hand it's during the coldest and darkest period of winter that soil drainage becomes the most crucial, and in the Pacific Northwest that is when our rainfall becomes much heavier. So there is the difference as you say. I guess it's not surprising then that some Mediterranean plants adapt well here and others don't.

The Olympic Rainshadow is actually rather large; it's just that a lot of it happens to be over water. It extends from Port Angeles over to Anacortes and all the way up to the Gulf Islands of BC to some degree.

Here is a link that might be useful: {{gwi:1073306}}

Hey that was a great map Ian, thanks.
I compared the January min-temp/rain because I think that perhaps no other factor determines nearly as much whether we can grow the Mediteranean plants or not. Factors like summer heat, sunny days, heating hours, yearly rainfall, rainfall from other months, etc., are all important (especially to fruiting/flowering), but don't come close to January min-temp/rain for basic survival.
After seeing your map I started comparing some of the island cities like Oak Harbor, Anacortes, Port Townsend, etc., and they are much closer in winter rainfall to Rome, some even less like Barcelona, although they all seem to lack the summer heat by a good 15-20 degrees average over the whole months of July & August.

Have any of you been out to Mesogeo on Bainbridge? They specialize in Mediterranean & similar plants. I love that place. :^)
- Tom

We may be a modified Mediterranean climate, but there's not too many Mediterranean plants that won't grow here easily, provided they have sufficient hardiness. I would agree that a requirement for good drainage is pretty much standard for all of them, but same can be said for many other plants not from Mediterranean origins. The primary factor that seems to favor their growth is our typically dry summers. Relatively mild winters (compared to more continental locations) and the rainfall patterns (winter wet, summer dry) also contribute to their flourishing here.

Some of the most common plants of Mediterranean origin are staples in NW gardens - salvias, lavenders, rosemary, thyme, many other herbs, anemones, many spring bulbs, hellebores and euphorbias, just to name a few.

Here is a link that might be useful: Mediterranean plants

The eastern Mediterranean appears to experience more of a precipitation spike in January. Looking at a place like Beirut it is not too far off from Seattle rain-wise. Of course that is pretty much frost free.

That is unfortunate, in a way, that the entire Olympic Rainshadow tends to be cooler in summer than much of the Northwest. Of course, nowhere in Washington matches Rome or Barcelona anyways heat-wise.

I participated in a plant sale last summer with Mesogeo. They had a pretty good turnout so it was worth it.

Unfortunately, "provided they have sufficient hardiness" eliminates a lot of my favorite Mediterranean plants... Aeoniums, Echium, Phoenix, Isoplexis, and many others. If you expand 'Mediterranean plants' to plants from other parts of the world with Mediterranean climates (especially in the Southern Hemisphere), you can add a whole lot more to that list.

Yeah, I was just feeling sorry for myself this morning over 3 echium that finally kicked the bucket. Almost made it, darn it. I'm still mad at myself for not protecting them better.
- Tom

Don't forget that higher elevations with more rain and cold are also within mediterranean climate zones both within the Mediterranean Basin as well as here in California. There are local microclimates here in the SF Bay Area that receive up to 70/80 inches of rainfall, while less than 5 miles away it might be only 30 inches. They are both mediterranean climates as they get predominantly winter rainfall and dry summers. There is no typical mediterranean climate; as an example, Rome gets more summer rainfall than southern Spain, and it can and does freeze and snow occasionally in both Rome and Lebanon/Israel. Coastal California tends to get summer fogs which actually allow our version of coastal rainforests to exist, such as the mixed conifer/oak woodlands/coastal Redwood forests along the wetter slopes. California tends to have a longer dry season than most other mediterranean climate locations, South Africa's Western Cape tends to have a shorter dry season, but a much windier climate year round with resultant higher moisture loss due to winds rather than lack of rain. There is no "typical" mediterranean climate, other than the fact that they all have predominant winter wet periods and dry summers, which are a rarity in the rest of the world, and represent less than 2% of the world's climate zones.

I would disagree about New Zealand not having microclimates that seem similar to a mediterranean climate. There are certainly areas that resemble one, with rather sparse summer rainfall, and generally mild year round temperatures. It might be interesting to note that tropical high elevation cloud forests often resemble climatic conditions of our northern California summer fog drenched mediterranean coastal areas, and Californian and other mediterranean plants do as well in these tropical high elevation environments as tropical cloud forest plants do in our foggy coastal California gardens.

Knowing the locations, elevations and habitat conditions of mediterranean region plants and the temperature range and rainfall totals is a better predicator of success for replicating good growing conditions than overgeneralizing, as there are plenty of higher elevation plants that are prefectly cold hardy and wet tolerant and also from mediterranean climate zones.

One generalization that is pretty easy to make successfully is tiny leaved, gray foliaged/waxy foliage plants from mediterranean zones will typically want full sun and excellent winter drainage to survive in higher winter rainfall zones such as the PNW, while succulent foliaged plants from areas that seldom freeze will be less successful in areas that stay very wet in winter and also freeze.

I also thought that the wet/dry seasonal pattern and generally mild winter temps were what defines a Mediterranean climate. Ours is [i]modified[/i] in that it is wetter and cooler than others.

And the point isn't that we can grow the all of same plants as in other Mediterranean climates (although we can grow many). The point is that the wet/dry pattern and mild temps are the dominant features of gardening here.

Bahia, I had always thought that when people spoke of a 'Mediterranean climate' that they were talking first about cities on the Mediterranean. If you expand that to whole countries to include inland cities in the core definition, then isn't the term virtually meaningless, kind of like saying 'I live in an American climate'?

Karchita I would agree that temps & rain can define us, but the only similarity I really see between Mediterranean cities and the PNW is the avg. winter lows.
We get more variability even in winter with lower record temps than they do, vastly more rain in winter(a key factor), less rain in the fall than they do, and we're not even in the ballpark for summer temperatures/heating hours/sun. I don't really see how we're even a modified Mediterranean?

I guess it depends on how narrow or broad a definition needs to be to have some usefulness. Since plants in general are usually able to adapt to climates that differ from where they are native to varying degrees, and quite a few Mediterranean plants do well in the Northwest, many people consider this designation to be useful. You could also say our climate has more similarities to a Mediterranean climate than to a lot of other kinds of climates around the world. For example we're certainly not a semi-tropical monsoon climate nor a polar desert.

Personally I think calling the NW a modified Mediterranean climate is useful because it reminds us that we have a summer dry period and a lot of plants from east Asia and the eastern US, even some European species aren't really as happy here as tradition might have us believe.... at least not without a lot of irrigation. And as our population grows no one is expecting irrigation water for plants to become a more plentiful resource in the future (although we are certainly blessed compared to some parts of the world). Many such plants obviously are popular because they perform well enough to content many gardeners, but having traveled around a bit I have to wonder why we bother with them when they do so much better in other parts of the world.

I read in a book once that many parts of the Pacific Northwest are a "temperate rain forest." Due to the amount of rain some parts get, and 'temperate' meaning colder than tropical.

Most places in the Northwest that receive 90-100 inches or more of rain annually are considered temperate rainforest from an ecological standpoint.... thick vegetation with lots of moss, ferns, etc. enough to create it's own humid meso-environment much of the time. (Interestingly, certain areas on the southeast slope of the Olympics and in the South Cascades receive that much precipitation and still maintain predominantly sclerophyll vegetation.) Even the wettest rainforests have a pronounced summer dry period with not enough summer rainfall to reliably support some non-native plants that might need it. For example in the dry summer of 2006 I drove out to Forks and everything there was parched and brown just like it was inland.

I would say we are a modified Mediterranean climate too.
Here in Portland I have a beautiful fragrant Jasmine plant that is quite large, and makes it through the winter just fine. It is in the ground, so it stays out all year. The Willamette valley is also perfect for growing grapes, very Mediterranean :P

I tend to think that it's a poor indicator to say 'this particular plant...', because almost any individual plant will have some specific examples growing in nearly any place with at-or-under it's minimum tolerated temp, and winter low temps are only a drop in the bucket on the overall weather picture.
A whole large genus, like all grapes, would be a much better indicator. I don't really know if the Wilamette valley is representative of the PNW, but if we said it was, let's consider what you brought up about grapes. I think grapes in general tend to show that climate is different, in that only cool-climate varieties are widely grown there, unlike in the Mediterranean.
Even there in the southernmost portion of the PNW, you still have double to triple the rain in the coldest months, and 10 degrees or more cooler in summer.