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Messages - kumin

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Cold Hardy Citrus / Re: F2 citrange winter hardiness trial
« on: February 15, 2019, 12:10:08 PM »
After a new survey of the F2 citranges, I remain cautiously optimistic. The best looking plants remain quite consistent, although a portion of previous candidates look less promising. The best contenders are likely well under 1 percent of total plants.

One factor in their favor is the fact that our area has had record high moisture levels since July of 2018. The plants should have been well hydrated at any time the soil hasn't been frozen. An other unanticipated factor may be the black plastic film used for weed control. I suspect this will lessen the freeze/thaw effects to some degree.

There's an attached photo of a Southern Magnolia cv. 24 Below. This is included to gauge the impact our cold event had on other plants with hardiness similar to Poncirus. All cold damaged leaves will be shed during the May flush of new growth.

Cold Hardy Citrus / Re: Citrus in the Pacific Northwest
« on: February 10, 2019, 05:56:03 PM »
Thanks for the post. Providing the weight of the snow doesn't cause damage, snow per usually protective against low air temperatures. Growth above snow on the other hand can be very vulnerable, depending on atmospheric conditions. This event should be informative, after there's a chance to evaluate the outcome and subsequent recovery. Wind is a mixed bag, it contributes to desiccation on one hand, but also contributes to temperature uniformity helping to prevent super-cold air accumulation in low lying areas.

Cold Hardy Citrus / Re: F2 citrange winter hardiness trial
« on: February 08, 2019, 04:34:39 PM »
This continues to be an educational experience. The local cold weather has been followed up by warmer temperatures and rain.
 A few observations:
1. Poncirus leaves and twigs that appeared to be wilted and dying have re-hydrated remarkably quickly.
2. The combination of direct sunlight and frozen soil is very dehydrating.
3. Subzero temperatures with no wind on a clear night allows a super-chilled  layer of air to form directly on top of the snow, which is very harmful, this layer was about 6" deep. I don't have record of the actual temperature of this layer, as the reading of -11.8 F. was about 30" above the snow.
4. The section of the stems above the bottom 6 inches showed considerable less damage than the lower 6".
5. The rather quick warming trend allowed some damage to be visible within days.
6. Some bark splitting is becoming apparent.
7. There will likely be additional observations over the next 6-7 weeks, perhaps longer.
8. Photos of Poncirus before warm up and after warmup and rain. This should be the same twig.
9. This Poncirus tree was planted in the early 90's.

Cold Hardy Citrus / Re: F2 citrange winter hardiness trial
« on: February 06, 2019, 09:11:25 AM »
Thanks, I am hopeful. Both photos were taken today and both plants were exposed to the same temperatures. I realized that there are still many weeks until April 1. when I consider all danger to be past.

I have noticed that the slight red color where the leaflets join is not an indication of cold adaptation, but rather an indication of tissue damage.

Poncirus indication of cold damage closely parallels that of the citranges. A few of the citranges appear to have hardier leaves than the Poncirus progenitor, this may only be because Poncirus would have dropped it's leaves at that degree of maturity on that position of the stem.

Cold Hardy Citrus / Re: F2 citrange winter hardiness trial
« on: February 06, 2019, 08:04:37 AM »
Here are 2 photos showing responses of:

 # 1: F2  citrange seedlings and  the variability in cold resistance after a cold week with a low of -11.8 F. at the lowest.

 # 2: Poncirus  that hadn't dropped it's leaves.  Observed on a plant not fully hardened off.

Cold Hardy Citrus / Re: F2 citrange winter hardiness trial
« on: February 03, 2019, 05:58:59 PM »
At this point I'm debating protecting a few of the most promising specimens for the rest of the winter, in order to preserve their genetics. It would be a deviation from my original plan, but I already have $2,000.0 in this project and it might be prudent.

Although I can be certain that the seed parent is F1 C-35 citrange, there is no definitive proof that the pollen parent is the same. Depending on blooming time and seed grove layout, the pollen parent could be  potentially be a citrumelo, or different citrange.

Cold Hardy Citrus / Re: F2 citrange winter hardiness trial
« on: February 03, 2019, 03:30:55 PM »
Today's high temperature is 45deg. F. I've taken a few photos to see how the best plants have fared. Most look similar, but a little worse for wear and tear. The best ones look to be in similar condition to my Poncirus of similar size. These may have a chance at survival.

This is after almost a week of temperatures below freezing, the lows ranged from +3 deg. F. to -11.8 deg F., there were several days of high temperature +/-  +15 deg F. I am pleased with the results thus far, but percentages of plants looking this good are low.
Of special interest to me is plant # 3 having a mixture of unifoliate and trifoliate leaves.

Cold Hardy Citrus / Re: F2 citrange winter hardiness trial
« on: February 01, 2019, 01:45:57 PM »
The present low temperature event has struck the local area. Recent daytime highs are approximately +15 deg. F., today is expected to reach +20 F. Local lows have been +3 F,  -11.8 F, +2 F and tonight + 10 F. The - 11.8 F reading was considerably lower than the forecast. These midwinter temperatures aren't a problem for Poncirus. Concerning the F2 citranges, however, this is a severe test. I will survey the plants again once we get a prolonged thaw .  Survival is obviously not assured. A thaw is forecast to begin tomorrow. If any manage to survive they will be protected in subsequent winters.

Cold Hardy Citrus / Re: F2 citrange winter hardiness trial
« on: January 29, 2019, 12:40:52 PM »
Ilya11, I agree with you. It's very likely that being evergreen puts too much stress and demands on the plants. There are a few plants that have dropped their leaves. I am not certain if this is from stress or preparation for winter. The trees I favor at present may not be the best in the next several months.

Cold Hardy Citrus / Re: F2 citrange winter hardiness trial
« on: January 29, 2019, 11:59:46 AM »
Ilya11, There is considerable variation in leaf color, some are very dark green, some are showing a bronzing response to the cold. Others show a reddish tint where the leaflets join the petioles. The F1 seedlings are uniformly dark green and shriveling as they desiccate. There are a number that have a yellowish cast, but most leaves have not dropped at this point.

One thing to keep in mind is that straight Poncirus often isn't reliably deciduous until the third year. I'm attaching a photo of self seeded 2-year old pure Poncirus that have changed color somewhat, but still haven't dropped their leaves.

Cold Hardy Citrus / Re: F2 citrange winter hardiness trial
« on: January 28, 2019, 08:08:51 AM »
Mikkel, thanks for the winter hardiness information. It's apparent there's a great deal of variation between individual cultivars.

Cold Hardy Citrus / Re: F2 citrange winter hardiness trial
« on: January 27, 2019, 05:38:31 AM »
Thanks, Mikkel the reversal of the hybrid retaining the fruit while dropping the leaves is interesting. One aspect of Poncirus fruit is the rapid dropping of the fruit followed by short storage life. I have no experience with the variability of Poncirus hybrids fruit storage life.

Cold Hardy Citrus / Re: F2 citrange winter hardiness trial
« on: January 27, 2019, 04:56:13 AM »
Ilya11, Yes, it was a strictly controlled alkali treatment followed by water flushing, again followed by weak acid rinse. then flushed repeatedly. At this point the final 24 hour soak was begun. I've just noticed I referred to the process as "stratification" my intent was to say "scarification".

Cold Hardy Citrus / Re: F2 citrange winter hardiness trial
« on: January 27, 2019, 03:26:06 AM »
Photos taken yesterday of one plant lacking hardiness and one showing little damage.

Cold Hardy Citrus / Re: F2 citrange winter hardiness trial
« on: January 26, 2019, 06:42:50 PM »
Ilya 11 Thanks for your suggestion of a leaf taste test. During field planting I noticed some plants were pleasantly sweetly aromatic, but I didn't trust that there was a definitive correlation between plant sap taste and fruit taste. Relying on such a test could dramatically reduce the time, labor, space, etc. required to plant seedlings.

Cold Hardy Citrus / Re: F2 citrange winter hardiness trial
« on: January 26, 2019, 04:32:51 PM »
The germination technique I used, was placing the seeds in mesh bags, then using a repurposed dishwasher with thermostatic control of water temperature, aerated/soaked them for 24 hours at 86 degrees F. I then removed them and scarified the seed coat for 30 minutes, followed by neutralizing the solution and rinsing them thoroughly. They were then returned to another 24 hrs of soaking, followed by planting immediately into a germination bed, again at 86 degrees F. They were planted 1 centimeter deep. Areas cooler than 86 degrees had a bit of seed decay. Seeds planted too shallow lifted out of the soil. Seeds planted too deep had delayed emergence. Emergence began at 7 days and continued a little over a week.

 The seed soaking procedure was used, as the seed was stored, dry seed. This would be unnecessary with fresh seed. Soaking the seed helps to synchronize the germination and subsequent emergence of seedlings.

The water used in the soak was slightly chlorinated to prevent decay. The water was drained and replaced every 6 hours. As the seedlings grew larger and May weather became warmer the bed temperature was dropped to 75 deg. F. The seedlings were field planted on June 12, 2018. By end of September the tallest seedlings were 48" tall. The average was closer to 30" - 36 " tall.

Cold Hardy Citrus / Re: F2 citrange winter hardiness trial
« on: January 26, 2019, 02:59:03 PM »
3,000 is a little less impressive than it sounds, approximately half are genetically dwarf which is not unusual for F2 zygotic citranges. Many of them are too lacking in vigor to hold much promise. Long story short- I did a status survey today and believe 100 to 150 plants are relatively unscathed, but February can be brutal to plants. Some winter cold damage is accumulative, as any individual cold event can be. The best looking plants phenotypically favor Poncirus rather strongly. However, they are not identical to one another in appearance. Hopefully they will carry some Citrus genes.

Cold Hardy Citrus / Re: Winter care of citranges, etc.
« on: January 25, 2019, 10:11:17 PM »
About 30 years ago, I had a budget solar greenhouse 20' in diameter. The structure was 15 sided 4' per side  The perimeter had foam insulation board 48" deep in the soil. The north wall had 6 - 275 gallon black water tanks set upright. The northern 2/3 of the wall and roof were insulated. The southern 1/3 of the roof/ wall was double wall polyethylene. When the weather warmed up the plastic film and roof insulation were removed.

This structure was used to house citrandarins. I never saw frost inside the greenhouse.

Cold Hardy Citrus / Re: F2 citrange winter hardiness trial
« on: January 25, 2019, 07:53:36 PM »
Walt, being of similar age as you, I am using brute force (large populations) in an attempt to increase the odds of obtaining very hardy F2 segentranges in a short time span. After planting a number of putative " cold hardy " cultivars that failed, I am seeking plants with nearly the full hardiness of Poncirus.  I began with an initial population of 20,000+ seedlings. The seedlings are 85% nucellar and 15% zygotic, so the effective population under trial  is 3,000 plants.

The seeds were germinated in April of 2018 and planted outdoors in June, 2018. These plants are not protected against the cold in any way. Survivors, if any, will be protected going forward, knowing they have the necessary genetics. At this point the population will be very small and easier to protect.

Googling  "citrus tree seed California" will give you 2 hits that sell seed by liter or quart. If you need details on how to germinate large quantities of Citrus seed I can't make a recommendation, but I can tell you how I did mine.

Cold Hardy Citrus / Re: F2 citrange winter hardiness trial
« on: January 25, 2019, 01:58:21 PM »
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.

Cold Hardy Citrus / Re: F2 citrange winter hardiness trial
« on: January 25, 2019, 01:42:38 PM »
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.

Cold Hardy Citrus / F2 citrange winter hardiness trial
« on: January 25, 2019, 08:04:22 AM »
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.

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