Impressive Resource For Northern Planters

Was just alerted to the existence of the following website by a post from the creator on Growing Fruit:

https://www.pomologica.ca/

It has all the data you could ever want on cold-hardy varieties and their breeders, lineages and other details.

Awesome, really.

Very interesting site

The site goes on about "northern" and "here".  Where is that?  Not knowing makes it hard to use the resource.  The dates don't add up to European history, so I'm guessing north america?  

The link to the 'nursery' (presumably the originator) seems to be in Southern Manitoba, so Canada I believe.

Manitoba, correct.

The creator is in Zone 3.

Thanks.  I wish they could have said that on their site.  It makes a big difference how we can use the site.

Nancy Reading wrote:The link to the 'nursery' (presumably the originator) seems to be in Southern Manitoba, so Canada I believe.

Yes, quite likely from the Morden Research Centre which is SW from Winnipeg.  This is an Agrifood Canada (Federal research entity) station and coupled with trials in Saskatoon and Lethbridge give good data for hardiness from the Canadian Rockies back through Ontario.  Several tree varieties out of southern Manitoba are sold at nurseries in North Dakota and northern Minnesota in the US as these come with strong genetics for productivity in our soil types and tolerance to cold winters.

John Weiland wrote:

Nancy Reading wrote:The link to the 'nursery' (presumably the originator) seems to be in Southern Manitoba, so Canada I believe.

Yes, quite likely from the Morden Research Centre which is SW from Winnipeg.  This is an Agrifood Canada (Federal research entity) station and coupled with trials in Saskatoon and Lethbridge give good data for hardiness from the Canadian Rockies back through Ontario.  Several tree varieties out of southern Manitoba are sold at nurseries in North Dakota and northern Minnesota in the US as these come with strong genetics for productivity in our soil types and tolerance to cold winters.

The Creator runs a small nursery.

Montana Fruit Trees carries a number of the varieties mentioned on the website.

Now if only there was a "order one of each" button. :-)

r ransom wrote:Thanks.  I wish they could have said that on their site.  It makes a big difference how we can use the site.

Great resource!

They do mention their location in the "About" tab. Perhaps it should be more prominent, given the different "Zone" systems used in Canada and the US. Perhaps the UK and EU have different systems also?

Nice there is an about tab there now,  i couldn't find it at the top or bottom of the page yesterday.

There is good information in the about page that makes it easier to use the resourc and explains why the dates for the species are so recent. They are using the dates the fruit came to that region.

I hope they add more about day length and how it influence fruit production. That's the major problem i find living above the 49th.  Temperatures is important, but if the day length needs is awkward, it's tricky to get a harvest.

Bookmarked, thanks for sharing. The day length point is a fair one, it catches people out more than temperatures sometimes, especially anyone used to using zone maps from further south.

Douglas Alpenstock wrote:Perhaps the UK and EU have different systems also?

Well, yes and no. Mathematically EU and US are mostly identical, but in practical gardening, they are worlds apart. Here is a quick breakdown of what you need to know (I will use Poland as example).

The Similarity: The Thermometer Formula

On paper, the baseline is exactly the same. Both US Zone 6 and Polish Zone 6 are defined by the average annual minimum winter temperature:
• Zone 6a: -23.3°C to -20.6°C (-10°F to -5°F)
• Zone 6b: -20.6°C to -17.8°C (-5°F to 0°F)
If you are growing hardy herbaceous perennials (like Echinacea, Hostas, or Daylilies), they behave identically. As long as their roots don’t freeze past their genetic limit, they will pop back up in the spring whether they are in Ohio or Masovia, Poland, EU.

The Major Differences: Summer Heat & Latitude

The thermometer only measures the single coldest night of the year. It completely ignores what happens during the other 364 days.

"Wood Ripening" (The Summer Heat Factor): Summers in the US Zone 6 (Midwest/Northeast) are hot, humid, and consistently sit between 30°C and 35°C. This intense thermal energy cooks the plants, allowing new tree branches to "ripen"—meaning the soft green growth turns into hard, woody bark before winter. Central European summers are much milder. Without that intense summer baking, plant stems stay soft and green, making them highly vulnerable to freezing when winter hits.

The Latitude Illusion: Poland sits around 52°N latitude (parallel to central Canada). The US Zone 6 sits much further south, around 40°N latitude (parallel to Madrid, Spain). Because the US is further south, it gets much higher light intensity and stronger solar energy year-round, even though its winters drop to the same freezing temperatures as ours.

Real-World Examples

• Figs (e.g., Chicago Hardy): In the US Zone 6, this variety can grow into a large, productive woody shrub because the blazing American summer hardens the wood to withstand the winter. In Poland's Zone 6, that exact same fig tree will almost certainly die back to the ground every winter unless heavily wrapped, because our milder summers don't ripen the wood enough.

• Peaches and Grapes: US Zone 6 gardeners grow these with massive success. In Poland, even if the plant survives the winter cold, our lack of intense summer heatwaves can lead to poor sugar development in fruit, and sudden European spring frosts are notorious for wiping out buds much more aggressively. Only a few areas of Poland with specific microclimate are good for grapes.

So, we use US-adapted zones but we do not trust them blindly for woody shrubs, fruit trees, or Mediterranean plants.

A plant rated for "US Zone 6" might need a Zone 7 or 8 microclimate in Central Europe (like a south-facing brick wall or a greenhouse) to make up for the lack of summer heat.

As to the UK, (as far as I know) they have their own RHS system of zones, from H1 to H7.
• H1–H2: Tropical to frost-sensitive
• H3–H4: Half-hardy to hardy (H4 roughly matches USDA Zone 8)
• H5–H7: Very hardy down to continental European winters (H7 roughly matches USDA Zone 5 and below).

Joao Winckler wrote:........The day length point is a fair one, it catches people out more than temperatures sometimes, especially anyone used to using zone maps from further south.

Thanks for the note above about the "About" tab at that excellent website introduce by the OP.   And yes, so many factors other than daylength and temperature swings.  Part of the reason we look to Manitoba so much in our region is because we are in the northern Red River Valley...and the river is what remains of a glacial lake bed.  The lake bed is very heavy in clay and has a high water table....so there are many trees that dislike that combination of wet feet and poorly draining soil.  The Valley actually widens as you follow the river north, first to Lake Winnipeg, then onward eventually to Hudson's Bay.  But the expanded Valley in southern Manitoba, flat and heavy-soiled, means that tree, shrub, and other plant varieties that can grow in it and that far north likely will do pretty well in our area as well.    Most of the local apple orchards here are found starting about 20 miles to the east of us:  That is where the old "lakeshore" of glacial Lake Agassiz begins and the soil is sandier and less heavy.

That does seem like a useful resource.

A side note about growing zone systems: Some countries have their own zone systems, which are not necessarily at all equivalent to the USDA system. For instance, Norway, Sweden and Finland all have their own systems, which are roughly equivalent to each other, but not quite. They all run the opposite way to the USDA system (lower number is warmer) and take more factors into account than winter minimum temperature. Trying to translate USDA hardiness to any of these is... challenging. Our place is in Norwegian zone 4. According to the maps I've seen, it's placed in USDA zone 6. However, since it's heavily oceanic, the winters are longer and harsher than you'd expect for a similar minimum temperature elsewhere. I generally think that things hardy to USDA zone 5 might work at our place, but as always, it depends.

Canada's original zone formula from the 1960s

Their formula is:

Y = -67.62 + 1.734X₁ + 0.1868X₂ + 69.77X₃ + 1.256X₄ + 0.006119X₅ + 22.37X₆ - 0.01832X₇

where:

Y = estimated index of suitability
X₁ = monthly mean of the daily minimum temperatures (°C) of the coldest month
X₂ = mean frost free period above 0°C in days
X₃ = amount of rainfall (R) from June to November, inclusive, in terms of R/(R+a) where a=25.4 if R is in millimeters and a=1 if R is in inches
X₄ = monthly mean of the daily maximum temperatures (°C) of the warmest month
X₅ = winter factor expressed in terms of (0°C - X₁)Rjan where Rjan represents the rainfall in January expressed in mm
X₆ = mean maximum snow depth in terms of S/(S+a) where a=25.4 if S is in millimeters and a=1 if S is in inches
X₇ = maximum wind gust in (km/hr) in 30 years

https://planthardiness.gc.ca/?m=1
There is also a translated map on that site using usda numbers

It's updated and formula adjusted every 10 years or so, as they learn more about different climates.  

It's also interesting that it's focused on perennial shrubs and trees, and not designed for annual crops like most seed catalogs say.

Just came here to let you know that I took some feedback to the creator and he was happy for the feedback and made some changes.

I'd encourage you to reach out via the Contact tab on the site and let him know what you like and what you'd like to see added or clarified.

He wants to the resource to be as valuable as possible.

He's released a few new updates, as of today, dealing with hardiness zones and related data.

Go take a look.

r ransom wrote:Very interesting site

The site goes on about "northern" and "here".  Where is that?  Not knowing makes it hard to use the resource.  The dates don't add up to European history, so I'm guessing north america?  

North america, we're in southern Manitoba but I'm growing cultivars from cold areas in Europe and Russia so I wanted to just call it northern.  We're in zone 3 here, and that covers a good piece of Canada but the same temperature bands run through other countries, just the zones are all different systems.  I made some maps this week that try and tie Northern together.  https://pomologica.ca/scales/world     If there's cultivars of anything that we can grow here that lines up to European history I want to add them.  There's a few plums that are kind of borderline can grow in zone 3/4 but most of them are modern.  

r ransom wrote:Thanks.  I wish they could have said that on their site.  It makes a big difference how we can use the site.

Feedback appreciated, I added some details in the about on the site, and it's really a zone 2-3 focus for what's listed, there are other sites that try and list every single apple cultivar and that's cool, but I'm mostly just tracing the ones from breeders and research stations on the prairies or nearby cold areas, and native species.  https://pomologica.ca/breeders

r ransom wrote:Nice there is an about tab there now,  i couldn't find it at the top or bottom of the page yesterday.

There is good information in the about page that makes it easier to use the resourc and explains why the dates for the species are so recent. They are using the dates the fruit came to that region.

I hope they add more about day length and how it influence fruit production. That's the major problem i find living above the 49th.  Temperatures is important, but if the day length needs is awkward, it's tricky to get a harvest.

will do some searching for these, good suggestion

Eino Kenttä wrote:That does seem like a useful resource.

A side note about growing zone systems: Some countries have their own zone systems, which are not necessarily at all equivalent to the USDA system. For instance, Norway, Sweden and Finland all have their own systems, which are roughly equivalent to each other, but not quite. They all run the opposite way to the USDA system (lower number is warmer) and take more factors into account than winter minimum temperature. Trying to translate USDA hardiness to any of these is... challenging. Our place is in Norwegian zone 4. According to the maps I've seen, it's placed in USDA zone 6. However, since it's heavily oceanic, the winters are longer and harsher than you'd expect for a similar minimum temperature elsewhere. I generally think that things hardy to USDA zone 5 might work at our place, but as always, it depends.

started to answer some of this here https://pomologica.ca/scales  , should add more about the other systems.

(edited) I've been doing some work on maps in this area and this is an update about to be posted, it tries to show some mapping that answers your question.  the zones don't line up exactly with the temperature data available so it's not as simple as the USDA zones that only use temperature

Welcome Doug!  I believe we chatted a bit at a Seedy Saturday at the Winnipeg Millennium Library a couple years ago.  We drove through the Brandon area this afternoon on our way home from Edmonton.

I was going to respond to this thread, but I was on the road, and everything seems to be resolved.

I placed my first nursery order with Oak Summit the weekend nearly two weeks ago and the order was received the beginning of the following week - we are relatively close for shipping, but I was suitably impressed.  I'm excited to see if I can nurse our new Siberian C peaches through our winters (I had missed the zone 4 / 3 warning in the description...my bad).  

Now I need to dig into this site...added to the list.  

I'm kind of skimming through this (have major RL distractions going on at the moment, sigh), so I probably missed it, but if it wasn't already mentioned, elevation is extremely important, too. That's why Sunset Magazine developed a gardening guide specifically for the Western half of the US, because you can be in a southern latitude but gardening at such a high elevation that you can have frost in any month of the year.

Gardening guides for the North are interesting to me even though we now live in Kentucky, because I grew up in Alaska. Too old to want to go back now, but still have family there who can use information like this.

feedback here has been great.   I've been continuing the research downloading more old books and publications, and just putting together details into pages including tables and images when they're out of copyright. Sometimes a table says a lot.   A good example is cross pollination in cherry plums, it's a little mysterious - in some case one is a good pollinator for the other, but it's not reciprocal.    Here are a few of the new tables and images added to Opata https://pomologica.ca/fruit/159-opata as an example.     These old early 1900s articles might seem like ancient history, but it's often the best information available - it's more detailed and they cared more back then to actually do the large trials and they were excited about the future of these fruits.   Today I've tried to collect all of the cherry plums I can find as a germplasm and for stock plants at my little nursery, and they're great, I enjoy propagating them and I can't seem to grow enough.  I hear from Americans all the time that they're not widely available, and it's crazy because most of them are from South Dakota.  It's a hybrid western sandcherry bush that grows plums, the history behind them in Hansen's publications really is an interesting story and it's totally relevant today.  Finding the right pollinator combinations for them is in fact best done by reading the most relevant and up to date document on the topic - a study from 75 years ago. https://sherwoods-forests.com/Downloads/UMinnAgExpStation-Stone_Fruit-Pollenation.pdf