Can anyone spare a few cold hardy citrus seeds? I'd like to try some Poncirus trifoliata and some hybrids. I think I'm zone 6b now, but we used to be zone 5 and maybe will be again. I think I've got room to winter one in the garage, and I want to try one or two outside.

I can pay or maybe trade something.

Anyone in Europe I am looking for some too

Hi, the following information might not relevant to previous posts but the title:
Georgia, the country next to the black sea cost if famous for its cold hardy citrus plants. I am not aware of any local seed or plant companies (due to language barrier), but I think the region has a huge potential for seed hunting. A wise man once said that Kyrgyzstan is the plavce to search fo apple varieties, but for citrus go to Georgia.

One thing to remember with citrus, pawpaw and some other seeds is that they are from summer rain areas. Because of this, the plant always expects there to be water. Unlike apple seeds, which largely evolved in dry areas,   they never had to develop the ability to dry up and then resprout, so they invested their evolutionary energy elsewhere.  As a result, if these seeds dry out, they will not sprout. If you are going to ship them to someone, make sure they are in, say, a moist paper towel in a ziploc bag.
John S
PDX OR

Just for laughs, I got and idea: grow out citrus from the things you get in the grocery store and test their hardiness. Sounds crazy right? Well, I been doing it somewhat accidentally here. I got one citrus seedling from... Umm... Well, that's another problem yet to be solved. Anyway, it's citrus. We had a late frost in the green house. Killed most of the basil and other citrus seedlings. This little tike held out and should still be growing.... If I could only remember where I put it, again, that's another problem. Anyways, my research indicates with a little heat (from like Christmas lights) some normal varieties can stand down pretty low outside so, therefore it's not a far genetic stretch to make it a little more temp tolerant. Just requires patience. And yes! I second: do not chill or dry the seeds even a little bit. Have your dirt ready as you eat (or squeeze) the fruit. That's how I've gotten the best results. As for genetic stability, my research also indicates many citrus such as lemon, sour orange, and tangerine have stable genetics and therefore the fruit will likely taste just fine at 3, when they get past puberty.... well, as fine as a sour fruit tastes anyway. If not, you now have a tree that makes cleaning supplies and/or zest! Congratulations!

I have done quite a bit of that. Pomegranates and some of the citrus lived for a few years.  I eventually didn't have enough energy to focus on them, so someone more focused may have had more success.  I live in zone 8b/9a so it is more likely to work here than Ohio. Then again, it's more likely to work in Florida or SoCal than here.
John S
PDX OR

Weird your having trouble at 8b. I know they grow lemons on the Canadian coast against houses with Christmas lights.  You can YouTube videos of the guy doing it. He explains good methods. I'm pretty sure I saw some one growing inland on one video. I'm not sure how productive or long-lived it was, but it looked atleast 3 years old. I have figs and lemons ripening right now in Ohio, but they are in pots I can shelter. I actually love potted citrus in the winter, so I'm not trying to breed for this climate. There are figs that should survive here and supposedly this Chicago variety in trying out this year should fruit every year in this climate. So far it liked the summer. 😁

Maybe there's something in your whole citrus care technique that is causing death at zone 8b? So far I've had 3 potted citrus live 3 years with relative neglect before I either experimented on them too much or gae them away.

Try Citrus tree source.  http://www.citrustreesource.com/Products/Seed.aspx
They buy seed in huge quantities, so they are being nice selling seed by the liter.  Maybe there is an opportunity for a collective purchase or resale,  the trouble with resale would be USDA quarantines and state laws.

Hello AMit,
I am not talking about hauling pots indoors and out. That would be very easy here. Ive done it for years, but I'm not interested in that anymore.

Another thing that you probably don't realize is that geography can be quirky.  It is much colder in Portland in the winter than in Seattle or Vancouver BC, hundreds of miles to the north,  so there are many plants that survive there that often die here.  Medford OR, 250 to our south, is quite a bit colder in the winter than we are, and Klamath Falls, OR, also 250 miles to the south, is much colder than us in the winter. 
John S
PDX OR

John, then perhaps you are not actually dealing with a zone 8b/9, but are in a microclimate that more approximates a solid zone 8. Zone 9 is where citrus is traditionally grown. And the part of Canada that grows it out doors (not potted) all year is zoned colder than that. I'm putting the link to the video I suggested so you can take a look and evaluate for yourself.

https://youtu.be/XX-R8sq6-vg

I like my potted citrus, especially since they are green, fruit covered and flowery during winter indoors, but I used to work with citrus growers in zone 9 before moving to a northern climate and did research on their potential in other areas. 

How much light do they need if they are indoors in the winter? Would a big east facing window be enough?

How big of a pot do they need to be in to fruit?

I got a meyer lemon early this summer from a greenhouse in a pot that is about 12" across.  It had 7 immature lemons on it and they are now ripe.  It is flowering right now and to my amazement it is putting out about 25 flowers.  The plant is only 12" tall so I can't imagine it will ripen all that fruit.  I'll be bringing it inside this winter and hopefully it will get enough sun...

Not to drive traffic elsewhere but there is some great info on this Tropical Fruit Forum that may be helpful.

My lemon tree, 4 yo, spends about 8 mo inside in a sunny east-facing window in Ohio. It's a dwarf and is about 3.5' tall, including the container. It is in a 6" deep 2' wide window planter with some decorative house plant that seem to tolerate abuse well. The most difficult part is fertilizing and watering. It gets a little interveinal chlorosis (magnesium deficiency) sometimes and I had to learn to only use in-door safe fertilizer in winter, (i.e. liquid). It's fruited two years now. Knocking off some fruit makes others larger, and insuring it's well cared for helps too. I thought I'd have to turn it every once in a while to even out sun exposure, but I found plants like staying in one position (who woulda thought?). The most challenging part of transportation is size, not weight. It's kinda funny walking through the house caring a tree. I tried bigger containers for other citrus and haven't noticed a real difference in growth rate yet, just makes a longer interval between waterings and heavier lifting for transport. In winter the regular waterings add humidity to our environment, so I don't mind.

Hello Amit,
I don't think you were reading what I was saying very closely.  I was trying to explain details of the climate but I don't think you are interested. I've been on gardening lists with guys in these areas for decades.  Good  luck with your indoor citrus in Ohio.
John S
PDX OR

Minus how many degrees is cold hardy? Kumquats take a few degrees under zero as do most citrus. The other question is weather the fruit ripens or not. Apparently oranges are hardier then lemons but they need the summer heat to ripen and don't get much taste here.

Hi John, I thought I was. I guess there's some miscommunication. I'll be pm-ing you to clarify.

Hello,
I feel compelled to post a comment here, even if this might be slightly off topic.
I harvested one fruit of my chaenomeles japonica "Cido - the nordic lemon" recently.
While this isn't a "true" citrus plant botanically, it was bred in Lithuania for cold climates where no lemons can be grown, as a substitute.
The fruit can be pressed and its juice can be used in the kitchen like lemon juice.
I was very positively surprised by the taste which really reminds one of real lemons.
The fruit contains a lot of vitamin C (more than lemons i think) and we cut some thin slices that we roasted in the oven with some fish (delicious!)
To those of you that live in very cold climates this might be interesting.
P.S. i did try poncirus trifoliata fruit and they are pretty nasty tasting in my opinion.

So cool Philip! I hadn't heard of that one yet, but now I'm going to want one!

Philip, you got me searching the web for this "nordic lemon".  I couldn't find Cido anywhere but there are plenty of chaenomeles japonica out there.  They are listed as flowering quince.  Is Cido a particular variety?  Where does someone get one of these?  Do you know how cold a zone they can handle?  Thanks!

Yes, Cido is the name of the variety. Plants for a future has chaenomeles japonica listed as hardy to UK zone 5 , whatever that exactly means.
Since it was bred in Lithuania it can handle some serious cold because it gets very cold there.
It can easily handle -4 Fahrenheit (-20 Celsius) i would say, maybe up to -13 Fahrenheit (-25 Celsius) but i am only guessing.
I can't find its frost hardiness indicated.

Unfortunately it seems to be very difficult to find it for sale in america.
Your best bet may be to find an English tree nursery that ships internationally.

A mature plant will eventually be about 5 feet tall and wide, so that makes it a lot easier to protect it from the cold aswell.
here is a link of an English nursery selling it, but they don't ship to america:
https://www.agroforestry.co.uk/product/cido-quince-chaenomeles-japonica%c2%85/

I just searched a bit more and you can't seem to get this plant in america.
The big waters dividing us make their presence felt once again.
I've been trying for years to get frost-hardy avocado varieties from america without success...

Thanks for looking Phillip!  As best I can tell, the EU and US zone maps are for similar temperature ranges.  I'm in zone 4a so it's a bit cold for this plant but I could maybe work it into a microclimate somewhere.  According to the EU zone map, zone 5 is a minimum temp of -20F.