Citrus > Cold Hardy Citrus

Citrus in the Pacific Northwest

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SoCal2warm:
Temperatures & Climate of PNW Cities

The city of Olympia, WA happens to be farther north than Duluth, Minnesota. Heck, it happens to be farther north in latitude than Quebec City in Canada. (Don't believe me? Pull out a map)
And yet it is possible to grow some limited varieties of citrus here, and I'm not talking about those yucky borderline hybrids of Trifoliate Orange.

Firstly, temperatures. Olympia is in climate zone 8a. Winter nighttime lows tend to be 27F at the lowest. Looking back at temperature records, there were two separate 3-day stretches where the nighttime lows dipped down to 19F. These nighttime lows were all preceded by sunny days where there wasn't the cloud cover and marine influence that helps moderate the temperatures. So ironically, if you see an anomalous sunny day during the coldest part of winter, watch out! That's probably when the plants are going to need protection that night.

Ironically as you head just an hour or two north you move into climate zone 8b. This is because Tacoma and Seattle sit right against the sound and all that water helps moderate the winter low temperatures. In Olympia, by contrast, a lot of the marine air from the coast has to move over 50 miles of land, and by that time has had a chance to cool down a few degrees. That's not to say Olympia doesn't get any influence from the sound, but the city sits at the very end of the sound, where it's narrower, and ends up not getting as much influence from it. So Olympia may get just a week of light snow in the winter whereas Tacoma may get nothing. Probably the spot with the most moderate winter temperatures is Point Defiance, which juts out into the sound. Not surprisingly there's a plant nursery named Jungle Fever exotics located here.

The overall climate in Olympia and Seattle is not that different, but there are some differences. Olympia tends to have slightly hotter summers. Olympia also has slightly less sunny days per year, though the difference is very slight. Olympia gets a little more rainfall, since Seattle is subject to some extent to the rain shadow effect from the Olympic mountains. Seattle does have slightly higher winter lows than Olympia, both because of its location and because of the extensive urban development in the region. As we move further north into Vancouver, Canada, the winter nighttime lows are yet higher still than Seattle. This is because Vancouver sits right on the water and gets more direct access to the marine influence from the Pacific Ocean (through the Strait of Juan de Fuca). Temperatures are overall about 2 degrees cooler in Vancouver than Seattle, it's just that the lows points tend not to be as low. Victoria, on Vancouver Island, is practically subtropical. Well, as close as subtropical gets in Canada. There's someone with a farm out there growing Meyer lemons! While it is really on the borderline of the temperature citrus can survive in, the huge amount of marine influence probably means there are not devastating cold spells that come along every so many years. This is the case in Olympia, which may occasionally have a winter colder than other years. You can grow regular varieties of pomegranates, but every 8 years or so there will be a devastating freeze that will freeze kill them all to the ground. (Slightly more cold-hardy varieties can survive though)

When you go south to Portland, the trend continues. Portland is warmer, but it's also further inland. This can sometimes mean freak hail storms some years. Overall, Portland probably has just a tiny bit colder lows than Olympia during the winter, but also warmer highs. Certainly it's warmer during the height of summer, where sometimes it can get uncomfortably hot for 2 to 4 weeks. It's worth pointing out here that Portland appears to be the northernmost extent of where roses seem to grow very well (hotter, dryer summers and the longer growing season).

It's fair to say that the temperatures are not a huge degree different from Portland to Vancouver (Canada) but there are some small but significant differences. More like an overall trend as you head north over this regional stretch. It's not a coincidence these major cities are located where they are. Usually going higher in latitude would make things colder, but in this case the major cities have progressively more marine influence as one goes north along this stretch, which helps counteract the difference in latitude.

In case you're wondering why the Northwest experiences much milder winters than the Northeast, it's because winds bring warmer ocean air inland. When it rains, that also helps prevent the temperature from going too low, because water vapor releases latent energy of heat as it condenses. The West coast tends to get most of its precipitation during the winter.

So the Pacific Northwest has mild winters. But it also has a short growing season. The winter lows might not be too bad but those temperatures don't start getting up to where citrus needs for growing until around May. And as much rainfall as the Pacific Northwest gets, the trees are probably still going to need some watering during the dry summers.

Citrus Varieties that can be Grown

Yuzu can definitely grow outside in the PNW. Bloomsweet grapefruit can be reliably grown with just a little bit of minimal protection during the winter, starting in late December. (Make sure the plant is grown indoors during the winter under a grow light, some place warm, and where the indoor humidity won't drop too low, for the first two years to give the plant a chance to get some time to become established, because young small plants usually are not able to survive cold very well, not until they get to 2 or 3 feet high)
Satsuma mandarins have been grown in Olympia, though they don't tend to produce very well without some minimal amount of covering.
Ichang mandarins or Citrus taiwanica (Taiwanica lemon) should be no problem.

Some Overall Thoughts about the Historical World Movement of Citrus

It is ironic, from one standpoint. There are actually so many plants from Japan that are commonly planted in the PNW now. There's a fair amount of influence from Asia (particularly Northeast Asia) in the PNW region, which has come across from the other side of the Ocean. But cold-hardy citrus has not been one of this influences. Even in Southern California, virtually all of the citrus varieties came from Florida or, in a few number of instances, Texas.

The reason citrus has traditionally been viewed as a climate zone 10 fruit (or zone 9 at best) no doubt has to do with history and geography. While Asia was the heart of citrus growing, the traditional varieties that we are most familiar with were brought to Mediterranean Europe via the Muslims from India. Oranges were already growing in Spain before Marco Polo's journey to China, so since Europe already had oranges and lemons of their own, the citrus varieties in Asia were not seen as such a novelty. With the exception of pomelo which could never be grown in Europe. That would later get bred into grapefruit though, which could be grown in Florida and parts of Texas. America was settled from East to West, originally by peoples who came mostly from Western Europe, so this had a profound effect on the varieties of plants under cultivation. The particular varieties might not have been the most suitable to the lands being settled, but that's what they had, that's what they were familiar with. This in large part explains why the Mid-Atlantic Northeast was the first region to be primarily settled, because the climate was so similar to that of England and many of the same crops were suitable to grow there. It also explains why the Spanish were more successful at settling lands with warmer dryer climates more similar to their own (like in Mexico, Texas, and Southern California). Pomegranate and quince were traditionally viewed as warmer Mediterranean fruits. It was not until just two or three decades ago that new varieties of these fruits were brought to America from Southern Russia that were more cold tolerant and disease resistant in wetter climates. Although the Northwestern part of Europe has a cooler wetter climate, they were only familiar with the lineage of pomegranate and quince that had reached them from the Mediterranean, and this carried over into America as well. It's the same story with citrus, the citrus known in Europe were only those varieties that had originally been taken from China to India and cultivated in India (approximately climate zone 10).

Meanwhile, there were cold-hardier citrus being cultivated in remote parts of interior China, and in Japan cold-hardier citrus varieties were being bred (primarily from Yuzu that had been taken from China).

Oranges were probably quicker to culturally disseminate over long distances, gradually making their way to Europe, than mandarins were (despite mandarins being the more cold-hardy of the two) because oranges have a thicker rind and longer shelf life, so the fruit could survive a longer journey, to be tasted by someone else from another culture. Of course the citron was known in the Middle East since ancient times. Just had to add some historical perspective in this post.

On the subject of Bloomsweet and its origins from Japan, please see my post in this thread: "Bloomsweet"
http://tropicalfruitforum.com/index.php?topic=22785.0 (it happens not to be posted in the Cold Hardy Citrus section which is why I'm giving you this link)

Thoughts on why the idea of trying to grow Citrus in the PNW never became popular

Well anyway, back on topic. While there has now been plenty of experimentation in Northern Florida, Texas, Georgia, and South Carolina growing citrus varieties outdoors, there is virtually no one in the Pacific Northwest growing citrus outdoors, despite the PNW being in the same official climate zone range.

And despite the PNW actually being much closer to the region of the world where all these cold-hardy citrus varieties came from (Japan and China). That's what I find so ironic.
Perhaps it's because all these areas (FL, TX, GA, SC) are so close to the citrus growing region in Florida. Whereas the PNW is so far away from Southern California, and in any case most of the citrus growing around the coast of California has since been destroyed due to the high land costs due to high population growth in that region. The commercial citrus growing in California has been pushed far inland, but then it can only go so far north before the winter lows get too cold.

So someone in South Carolina has commercial citrus groves growing a few hundred miles South of them, whereas someone in the far northern part of California has the San Francisco Bay area to the South of them. And then there are the coastal mountains in the northern part of the state, which means that the citrus growing would have to be very close to the coast, but then there is also all that coastal fog and clouds. It doesn't have those high temperatures and sunny weather citrus plants like. So I suppose the economics and geography on the West Coast are not as continuous as on the East Coast. On the East Coast it's merely a matter of temperature as you begin heading north from the Florida citrus belt. The region is much more flat, and surrounding land costs lower in the area we are talking about. What I mean is that, when you stop and think about it the reasons become pretty plain as to why there has been such little attempt at trying to start taking citrus northward on the West Coast; it's not such a natural progression or obvious inclination.

So maybe to summarize this post, there are reasons for everything, if we really want to examine them, but sometimes those reasons are kind of complicated.
I have so many thoughts here, hard to stay on one topic.

rfelsch:
What a wonderful post!  I recently moved to some Farm ground west of Portland (Banks, OR west of Hillsboro).  I am currently growing citrus and bananas in a hoop house.  I have Yuzu, Sudachi, Owari, Kishu, Gold nugget, Oro Blanco, and several others I am experimenting with.  I am hoping to see what can go outside, and what microclimate I can setup for them.  I am very eager to read more of your thoughts on the matter.  Again, thanks for the post.

SoCal2warm:
They recommend Poncirus rootstock to make sure the citrus goes into dormancy so it doesn't experience freeze damage.
In Portland, attempts at trying to grow these cold-hardy citrus outside with no protection generally have a 50% success rate. Whether a particular plant is going to be able to make it appears to be inexplicable. It's also worth pointing out that somewhere like South Carolina has a lot more heat during the Summer half of the year, so all that growth no doubt helps compensate for damage during a winter freeze. The PNW does not have that heat so much. If you really want your citrus to do well, that plant is going to need some transparent covering from Spring on to about May (give or take depending on how far north exactly you are). The plant may barely grow during this time but at least it will help prepare for Summer growth. The citrus should be able to keep growing until about September, when growth will slow to a standstill, though dormancy may not start until October, or even November.
(Covering in mid-October can be important just to keep the plant dry out of the rain to help it more seamlessly enter dormancy)

Fruit-bearing citrus in the PNW really needs some sort of covering for the first part of the year, and/or a good microclimate where it will get lots of sun and retain heat during the night. A large plastic bag covering and an LED bulb on an extension cord can work wonders, as well as putting some black-painted large containers of water inside the enclosure.

Again, young plants need protection. If it's under 2 feet it needs to go in a greenhouse or under grow lights during the Winter for the first few years (1 to 3 years).

Because of the high latitudes, and corresponding low angle of the sun in the sky during Winter, it's important to think about how sun exposure will change throughout the year in different spots. Before you plant, you might want to take a look outside during Winter at different times of the day to see which spots don't get much sun. This has more to do with trying to help prevent the plant from freezing at night. Put against a South-facing brick wall to help retain some of the sun's heat during the night. Or place a dark colored barrel of water behind it.

One guy even created a solar oven with a semicircle of reflectors focused on a black barrel of water with the plant in the ground right in front of it. Not sure how effective that was but it's an interesting idea. (Winter skies are completely overcast 85% of the time, but then again the coldest nightly lows usually hit right after the rare clear sunny days)


--- Quote from: rfelsch on May 12, 2017, 12:59:25 PM ---I recently moved to some Farm ground west of Portland (Banks, OR west of Hillsboro). I have Yuzu, Sudachi, Owari, Kishu, Gold nugget, Oro Blanco, and several others I am experimenting with.  I am hoping to see what can go outside, and what microclimate I can setup for them.
--- End quote ---
Unfortuantely where you are isn't going to be any warmer than Portland, because of those mountains blocking marine influence.

I do remember reading someone report about Sudachi being able to survive outdoors in Portland. It was protected from the wind.

Citradia:
I'm in the mountains of NC and I'm noticing that it doesn't get warm enough here for my citrus fruit to fully ripen before freezing temps happen in late October and growth just starting now in May. Despite stopping fertilizer in August, a final flush of growth happens in September. The growth that happens in September may survive through most of winter with raised tunnel and water Barrels, but invariably, all that growth gets killed by early spring; these are trifoliate hybrids and Ichang lemons I'm talking about. I started this cold hardy citrus adventure several years ago under the assumption that some of these trees were as touted, "cold hardy to 5 degrees F, or 10-15 degrees F with some protection ". Well, they're not. The only hybrid I have that didn't lose half of its height or more the past two winters is Dunstan citrumelo. The Dunstans left unprotected all winter did better than the other hybrids in high tunnel or the citradia with only water barrel protection. The tunnel was vented on both ends when not freezing at night to help keep trees dormant. The Dunstan in high tunnel looks good now in full leaf and all others look like crap; Ichang lemons, Thomasville ( it's actually just still dormant and leafless), citradia, nansho dai dai ( looks better than citradia or Ichang), rusk, mortan. My low this winter was 7 degrees and during the 80 degree February, my citrus started to break dormancy and put on little shoots of growth wether in or outside of tunnel. When we got two nights in mid teens in march/April, my trees were cut in half wether in tunnel or not, except for 5 out of seven Dunstans. Two Dunstans that Failed are planted out in open, not protected from wind, and are under black walnut tree which maybe weakens citrus afterall, even though I'd read that citrus isn't susceptible to juglone.  Bottom line, citrus, even trashy hybrids need heat and they don't like to freeze. If you live in south central FL or a coastal microclimate that looks like FL, you can grow citrus outside; otherwise, nontropical climate folks need to invest in plastic coverings and electric heaters for any outside citrus trees.

rfelsch:
Thanks for the additional information.   I built two 4'x20' planting beds insulated and heated with soil heating cables.  Both of these beds are inside my 20x30 hoophouse.  I am able to maintain 80 degree soil temperature throughout the winter with no problem.  The air temperature is another story.  I intend to grow most of my citrus in these conditions.  I intend to experiment outdoors with Yuzu, Saduchi and flying Dragon.  I fantasize about growing something more tasty outside such as an Owari or a another variety with better cold tolerance that I am unaware of.  This winter was exceptionally cold (got down to 7 degrees F. one night) (at least 3 weeks well below freezing) yet I was able to overwinter them with only a modest amount of supplemental heat.  I think I could use less heat by draping some agro-fabric over the trees on the nights below freezing and help them catch more of the heat radiating up from my soil.  Other than the several weeks of below freezing temperatures,  I did not heat the hoop house, just the soil.  I believe we have slightly milder winter extremes west of Portland because the occasional cold arctic blast that blows in from the east through the gorge dissipates up and down the valley without delivering the full force of that extreme this far west.  As you mentioned,  the radiational freeze on clear nights is the one to watch for. The other gotcha as you mentioned is the amount of light the trees receive.   Not sure how well I will be able to ripen fruit.  There is a guy south of here who was selling mandarins he grew in his hoop house.  I don't think he is using supplemental light.  He is heating it though.  When I measured the light inside the hoop house in the winter, it did seem to meet minimum requirements.   I think there is a significant amount of non directional light but the number of hours of light is low being North of the 45th parallel.   Not sure if the long days during the rest of the year will make up for the short days of winter.

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