Citrus ichangensis is often said to be the hardiest of the true citrus species.
Here in the UK, I have a plant growing unprotected outside for about 12 years. It has survived but not thrived, growing very little and rarely flowering. I have always put this down to the short, cool summers rather than the winter cold. It is only about 1m/3' tall with trunk about 2.5cms/1" diameter.
This winter has been the coldest for 30 years - although much more like the winters I remember when growing up in the 1960's. Minimum temperatures were around -8C/15F on several occasions, and below freezing every night for two months. Daytime temperatures rarely topped 4C/39F.
The C.ichangensis has suffered severe damage, with long splits on many branches. I doubt that it will survive.



Note this is not the Ichang Lemon, a hybrid more often grown in USA, bu the inedible papeda.
Citranges growing outside have survived with just some defoliation. Citrumelo and Ichangquat also seem fine.

Mike - typing with a broken right arm is hard work!

Mike,
Even potted Ichangensis Papeda had a hard time this winter here in Croatia, photo 2010-03-18:


The space used for overwintering citrus is staircase area of two story building. Assuming espaliered and relatively small trees there is enough space for all my potted trees. More cold hardy as well as bigger trees are kept at lower area levels. That area is not heated, house doors were opened on occassions even over night, because of our dog or even maybe dog was opening doors.
The result is that the trees being kept in lower half of staircase area have 10-20% of defoliation (frozen leaves). Nothing significant for them except for I. Papeda which suffers by far the worst.

One year old Ichang Lemon seedlings kept at middle staircase level are not damaged.
Sort of surprise is Faustrime which was kept in similar conditions as Papeda for most of the time. I'm expecting first Faustrime crop to be this year.
Morton Citrange has no noticed damage, will be planted into ground this spring. Morton is grafted on P.T. rootstock.

Troyer Citrange (in-ground since last spring) has been defoliated during 1st cold wave in December. Some branches dieback expected, overall the tree should survive, I think. Troyer is grafted on P.T. rootstock.

On local winter conditions:
"Judging solely on minimal temperature (2m level) this winter locally is USDA 7a.
Judging on low temp duration, ground coverage by snow... this winter seems to be the most hardiest in the last 60 years (just heard that from the local weather synoptic man).
I did some rough statistic:
since 1st November till 1st March we had 711 hours with temp <= 0C, 369 hours with temp < -4C. "
Above copied from:
link

Mike, good luck with your arm. Take care.
--ivica

Mike,
My in ground citrus ishangensis ( pure species bought from B.Voss) was dead several years ago after late winter freeze of -12C. I have a hybrid between C. ishangensis and kumquat that is still green and largely unaffected after incredible -16C that we had this winter, with weeks of frozen ground. I have impression that it is keeping dormancy for a longer time than pure ishangensis.

The splitting you see is because the tree was not dormant and the sap was flowing. When the sap is flowing and freezes it splits the bark as your pictures demonstrate. I have a seedling grapefruit that does this every year. I was sure it was a goner, but it comes back strong every year... The trunk looks like hell, but it doesn't seem to bother it and grows and flushes all spring & summer.

I won't give up on it yet, but unlike your vigorous grapefruit enjoying long, hot summers, this plant hardly grows at all in a normal English summer.
I will consider constructing a small plastic tent over it to boost temperatures a bit. That should encourage it to produce new shoots if the root system is undamaged.
IlyaC - Yes, my Ichangquat (growing very close to the C. ichangensis) appears to be fine. The dormancy trait from the kumquat parent clearly makes a hardier hybrid.

Citrange,

The trouble is not citrus ichangensis according to me, but YOUR citrus ichangensis in fact.

Your plant seems appearing unnormally weak. One can cleary see previous hard pruining signs, why? moreover, an important part of the root system is out of the ground.

I suggest the culture of this plant to be behind of its hardiness defection.

Franck

citrange wrote:

Citrus ichangensis is often said to be the hardiest of the true citrus species. Here in the UK, I have a plant growing unprotected outside for about 12 years. It has survived but not thrived, growing very little and rarely flowering. I have always put this down to the short, cool summers rather than the winter cold. It is only about 1m/3' tall with trunk about 2.5cms/1" diameter. This winter has been the coldest for 30 years - although much more like the winters I remember when growing up in the 1960's. Minimum temperatures were around -8C/15F on several occasions, and below freezing every night for two months. Daytime temperatures rarely topped 4C/39F. The C.ichangensis has suffered severe damage, with long splits on many branches. I doubt that it will survive. Note this is not the Ichang Lemon, a hybrid more often grown in USA, bu the inedible papeda. Citranges growing outside have survived with just some defoliation. Citrumelo and Ichangquat also seem fine. Mike - typing with a broken right arm is hard work!

C. ichangensis is not often available here. This plant was one of two rooted cuttings which I bought about 12 years ago.
I planted one outside, where it almost immediately died from root rot. The second one was kept in a pot for a few years, then planted outside on a slope which I thought would provide better drainage. I also planted it deliberately rather higher than normal, to avoid the trunk staying damp for too long. That is why you can see roots on one side of the plant. Perhaps that was a mistake, but at least it has not suffered from root rot like the first one.
The 'pruning cuts' you noticed followed another frosty period some years ago, which caused considerably die-back.
I know of only two other C. ichangensis growing outside in the UK. One is rather like mine and never seems to get significantly bigger. The second is in an extremely favourable south-facing position on the Isle of Wight, just off England's south coast. This is one of the warmest places in the UK and the result is a thriving tree several metres tall.
So, perhaps you are right and it has not been cultivated correctly. But I think that it is basically the wrong climate. It is too cool and wet in summer to re-grow after winter damage. Not like the South of France!

My climate is hotter than yours in summers and my plant was on poncirus roots, but overall it looked very similar, with slow and mainly lateral growth. It flowered, but fruits aborted quickly. I wonder if the clone available in Europe has some viral infection problems that affect its growth and hardiness.

Hi Mike,

regarding Ichangensis I do not belive that they are not suitable to the UK, especially southern England. The need of the heatsum seems not to be as high as for Poncirus Hybrids. Even in Hamburg, far northern than London, the growing during the saison is quite strong (partly more than 80 cm per year), but the hardiness is very disapointing. We had also the hardest winter for more than 20 years and I had nearly damages at any citrus (only exeptions were Trifolis, Hamlin x Flying dragon, Poncirus X Satsuma and Hybrid US 812), but the Ichangensis clons did even worse than all other Poncirus Hybrids. Below you can see some results from the last winter:



Heavy damage at the swingle





and here Poncirus X Changsha (also known as Hybrid US-852)



Anyway end of April will show whether they will survive or not.

best regards

Andy

Hi Andy,
What were your minimal temperatures this winter?

Hello Ilya,

unfortunately I did not place a min/max Thermometer near the tree, but official minimumtemperatur at the Hamburg Airport was - 16,5 C°. As my garden is a little more protected I prosume lowest Temp was around - 14 to - 15 C°. But more dramatic was a nearly 2 month periode without only a very few days of temps above 0 C°. This had a much deeper impact to the plants. So this winter was very selectiv and a good benchmark of real hardiness for the citrus.

How about your area ??? Which citrus did best ???

brgds

Andy

Andy,
Very bad winter even compared to the 2009 season that killed several of my citruses. We had three deep freezing episodes, each of ~2 weeks of frozen ground. The worst was in the beginning of January:



I had one degree warmer on my weather station.
I am normally not using any protection, but put some fleece over citremon on January 7 night.
It is most damaged, with large frost bite on the trunk, complete defoliation, and damaged upper twigs.
Also frostbites and defoliation on Morton.
Thomasville that is in a rather protected place, close to the wall and have damage on the upper part of the tree.
Citrumelo Batumi lost its leaves, but today I noticed appearance of flowerbuds ; last year it was defoliated but flowered a lot in the spring with plenty of fruits in autumn. HRS899J lost all leaves with some upper twigs damage.
Swingle citrumelo and Ichanquat have still leaves that are green. UnshiuXponcirus hybrid lost some leaves but otherwise OK.
Of course it is early estimations, since damage can appear later as infections from frostbites.

We have now warm days of 15-20C and poncirus is starting to flower.

Hi Andy, did your Hybrid US-852 tree have no damage? What does the fruit of the Hybrid US-852 taste like? Good or bad? Thanks.

I cut back all the badly split stems of the frost damaged Citrus ichangensis, just leaving the small main trunk - only about 6" (15cms) tall and about 1" (2.5cms) in diameter. Even this had some bark splitting, as you can see below.
Now at last it has started producing some new shoots:


Mike/Citrange

Mike, I would place a portable greenhouse over your tree to maximize growth and give it a fighting chance for the winter...Remember , we are halfway to Christmas

Cheers,

Greg