Citrus > Cold Hardy Citrus

F2 citrange winter hardiness trial

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kumin:
I'm trialing a population of F2 Citrange seedlings this winter in zone 6b in SE PA. There is considerable variability in the resistance to low temperatures, with some dying in November and others still viable at this point. The population is a mixture of nucellar  F1 and zygotic F2 seedlings. The F1 are freezing out at present, but a number of the F2 are surpassing the F1 in hardiness and a few appear to be surviving the winter. My hope is that several will approach the hardiness of P. trifoliata.

Any survivors would then be evaluated for palatability. My focus is centered on hardiness, with palatability being secondary.

I've grown poncirus since 1980 and lost everything above the snowdrifts in Jan of 1994. This was after 2 consecutive nights at -24 F. The trees resprouted below the snow height and haven't been injured since.

hardyvermont:

--- Quote from: kumin on January 25, 2019, 08:04:22 AM ---
I've grown poncirus since 1980 and lost everything above the snowdrifts in Jan of 1994. This was after 2 consecutive nights at -24 F. The trees resprouted below the snow height and haven't been injured since.

--- End quote ---

kumin, Thanks for this information.  Where are you growing poncirus?  Full sun, partial shade, protected from the wind?  Have you noticed any difference between poncirus plants? 

kumin:
hardyvermont, I have Poncirus plantings at three locations on the same property. All are in clay soil, one location  is well drained , the remaining two are poorly drained. The trees growing in full sun have the the most vigor. Last winter I removed a M. Grandiflora tree that was shading the largest Poncirus tree and upon release the Poncirus  tree responded positively. Most of my trees are fairly close to buildings which could block or concentrate the wind. I haven't recently germinated  Poncirus seedlings on large scale. When I did in the past, I saw the occasional seedling I suspected of being tetraploid. Due to generally having rather high % of nucellar (clonal copies) seedlings, one usually sees a lot of uniformity.

The citranges by contrast have no wind protection other than the density at which they're planted. They are planted at about 20 seedlings per sq. ft.

kumin:
hardyvermont, I lost a planting of first year Poncirus a few decades ago by planting them into loosely cultivated soil and not allowing the soil to solidify during the growing season. During the winter 500-600 succumbed to late winter frost heave. In early April I could very easily pull the dead trees out by hand. They were approximately a foot tall at that time. There were no survivors. Mulching the soil might have saved them all.

Walt:
What  is your source of citrange seeds?
I'm glad to know someone else in the USA is growing F2 citrus x trifoliate hybrids. But mine are still at the tiny seedling stage, certainly not ready to face zone 6 winter.  In fact,  I assume I'll need at least one backcross to trifoliate, maybe two.  I would love it if you proved me wrong.
Keep us up to date on your results

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