Hardy citrus trees for zones 6 and 7.

[Tim DH]

Hi Walt,
  Do you have a name for the 'edible' cultivar of trifoliate orange?

  I'm curious about the high grafting suggestion. My supplier recommended ultra low grafting!

  As it is, that's all a bit irrelevant since, initially, I'm not thinking of grafting anyway.

Tim DH

[Walt]

I just corrected my post on high grafting.  I left out high grafting on trifoliate orange, the winter hardy citrus relative.

The better tasting trifoliate orange (Ponciris trifoliata) has the name Ponciris+.  It is available in Europe.  Seedlings of it are in the USA.  Selfed seedlings it is believed.

[UnicornEmily]

I'd be interested in a citrus tree that is hardy to zone 7, makes fruit that tastes good, and is completely thornless.

Do those exist?

[pawpawPapi]

I'd be interested in a citrus tree that is hardy to zone 7, makes fruit that tastes good, and is completely thornless.

Do those exist?

Check out Virginia Fruit Grower, he is sure to have a citrus you maybe interested in.
https://www.youtube.com/watch?v=FC-1SVHTAt8&list=PL88FAo1sct2L4X1cw6Zo5ObOIl94QtPnM

[Tim DH]

So: This looks like it will become my next Rabbit Hole!

I've long fancied growing my own Marmalade, and I set off last Millenium with an expensive, (gifted to me,) Calamondin bush. It never really flourished, and died whilst I was on holiday.

Encouraged by what I had read on this forum (and others): Last year I bought some 'Fresh' Yuzu seed on Ebay. They came with some free Poncirus seed. But neither germinated.

In the Summer, one of our local budget supermarkets was selling little Calamondins for next to nothing. I don't now think that Calamondins are the way to go, but I couldn't come home without one! It's done really well. The problem with most citrus in England is partly lack of hardiness and partly they tend to fruit around Christmas (or later) when our light levels are really low. So there is little Sunshine to ripen the fruit.

A month or so later I found someone online selling little Yuzu seedlings, for not a little money. So, encouraged by the Calamondin, I got one of those too. It also looks quite happy despite the couriers best attempts to kill it.

NOW look what I've found! An online supplier of fresh Yuzu!! After I've harvested the seeds I'll be making some very expensive marmalade!!! (Curiously the seed does look somewhat different from my failed Ebay purchase!)

After many hours trawling the internet I've come to the conclusion that what I'm really interested in is the hardy 'long day' citrus, those that fruit in Summer rather than the usual (for Europe) winter fruited varieties. I never knew such things existed. Apart from Yuzu, I think the other two I stand a reasonable chance of getting are Sudachi and Kabosu. Here is a link to an interesting article about them:

https://citrusvariety.ucr.edu/sites/default/files/2022-04/crfg_article.pdf

Tim DH

PS Yuzu marmalade tastes (IMHO) good!

[Tim DH]

Some of my citrus seeds are germinating. Following the advice on the RHS website I initially set the propagator to 16^oC. ... However after a few weeks of inaction, I did a wider websearch and subsequently reset the propagator to 22^oC.

One of the Yuzus has come up like a mini tree!  The Sudachi seeds are more obviously polyembryonic. Does anyone have any tips on selecting FOR the zygotic seedlings?

Tim DH

PS Sudachi marmalade is also good!

[Jeremy Weiss]

One of the Yuzus has come up like a mini tree!  The Sudachi seeds are more obviously polyembryonic. Does anyone have any tips on selecting FOR the zygotic seedlings?

Only advice I can give is that the parthenogenic embryos will all look like the mother tree, and, more importantly, all like each other. So if you see a seedling that looks significantly different than all of its fellows, I suppose there is an enhanced chance of that one being zygotic.

Having grown some Yuzus myself, I can also tell you that if, in about two or three months, a shoot STILL hasn't developed any leaves, it probably isn't going to, and you might as well pull and discard it. Ditto any albino ones (I always got one or two in each batch.)

[Tim DH]

Hi Jeremy,
    What was your experience, growing the Yuzus beyond the seedling stage? Given your 'New York' location I'm guessing you didn't risk them in open ground?

Tim DH

[Jeremy Weiss]

Mixed. None of them ever got all that tall, since I tend to try and let nature do my thinning for me, and that doesn't work very well with decently healthy seeds. Plus I overplanted by a lot, as I usually do (a single Yuzu tends to have about 20-30 seeds and I put the seeds of four or five in the pot).

Eventually, I DID try and see how they would fare outside over the winter, since, in a previous year I discovered some were still green under the bark in the spring (I did not find this out until I had pulled them up as dead however, so I couldn't use that batch.) But that must have been a much milder winter, since, come that spring they were unequivocally dead this time. And since by that point I had realized I can no longer consume Yuzus (the Furocoumarins affect my statins the same way those in a grapefruit would) I never saw the point of trying again, at least until I found my "ideal" yuzu (one with a higher ratio of pulp to seeds/rind that the current commercial one, so I could get a decent amount of juice out of them.) I haven't brought out my sudachi (which should have similar cold hardiness qualities as a yuzu) due to the yuzu results. 

[Tim DH]

Candlemas tomorrow! So the darkest quarter of the year is just about behind us (in the Northern Hemisphere!) Actually I reckon the quarter point is on Feb 3rd, but Candlemas is close enough.

Thought I'd post an update on my Yuzu seedlings.

Yuzu1 I've decided to treat this one as an indoor plant for as long as I can, and prune it heavily. Two plants grew from the seed. It appears to have responded well to pruning despite the low light levels of the last three months.


All the rest are taking their chances in the cold greenhouse

Yuzu2 Two plants from one seed. Similar to Yuzu1


Yuzu3 The leaves on this one have been a different colour, right from first germination. Sort of slightly silvery.


Yuzu4 Was initially the most vigourous seedling. It branched straight out of the seed, whereas all the rest grew a single point. The branches have now mostly defoliated and the main leaves have gone too, leaving just the petiole wings.


Yuzu5 Medium sized, ordinary. My wife has suggested 'loosing' a few in the hedge to see how they do. Maybe next year.


Yuzu6 Another small one. I wonder if the degree of defoliation is a suggestion of genetic variability regarding response to the hostile environment.


I have read that Yuzus take 10 years to start fruiting. This is the start of year2. I wonder if pruning, or any other shock, might persuade them to flower a bit earlier. Also, since I do appear to have a bit of genetic variability, I wonder if 'years to maturity' is variable. One paper I read suggested that Hana Yuzu could flower in Year2, but I wasn't clear if that was from seed or cuttings. A three year generation time would greatly improve my chances of doing a bit of breeding! A ten year generation time means I'm more likely to be pushing up daisies than picking Yuzus!

Tim DH

[Tim DH]

I have a parallel set of Sudachi, but I'm less interested in them. They are reputedly less cold tolerant. Also I prefer Yuzu Marmalade AND the cutting of the Yuzu make very nice tea but the Sudachi cuttings don't!!

[Tim DH]

Two years into growing citrus seedlings... I've just stumbled upon this:

Rapid Evaluation System For Fast Flowers on Citrus Seedlings https://www.youtube.com/watch?v=LYa5PmfdyEk

The video is a bit long for the amount of info. but if it shaves a year or two off first flowering/fruiting I'll forgive it! Either way, since I've got a few seedlings to play with it'll be interesting to treat some differently.

[UnicornEmily]

Have any of you guys tried seeds from Tough Citrus?  I keep eyeing his seeds and thinking, "I wanna have some of those tasty fruits with trees that are hardy to zone 7a!"

[Tim DH]

Hi Emily,
     Interesting website. ... Not seen that one before.

     All the seed offered has poncirus trifoliata in its parentage. All trifoliate hybrids have a (greater or lesser)reputation for resinous flavours, which some find more unpalatable than others.

     My own aim is to grow fruit for marmalade making, rather than fresh eating.

     'Long Day' citrus (like Yuzu), which fruit in Autumn rather than Winter, look like a sensible way forward. I've been encouraged by the phenotypic variation in my seedlings, which were culled from 'shop bought' fruit.

     The reputation of citrus for taking 10 years from seed to fruit is a bit discouraging!

[Paul Anguiano]

Themulberries have evaluated a lot of varieties in the last year and compiled this hardiness table:
https://themulberries.org/citrus-fruit-rating-vs-cold-hardiness/

The individual score sheets are here https://themulberries.org/cold-hardy-citrus-taste-tests/