I was going to wait a bit for the full extent of the damage of our winter down here in Vancouver Wa, across the Columbia River from Portland Ore, but I may as well report on what's currently observed.
In fact, we've had two back to back hard winters down here, with the winter of 2022-2023 being primarily three Columbia River Gorge wind events with temperatures down to 18F, accompanied by East winds up to 40 mph. Those winds caused a surprising amount of damage to certain varieties, despite the relatively 𝘮𝘪𝘭𝘥 18F.
This past winter of 2023-2024 was closer to a true arctic event.
Winter of 2022 to 2023:
December 21st to 24th 2022:
low temperature of 20F(-6.6C) with 30 consecutive hours ranging between 20 and 22F.
sustained winds of 15-20 mph, with gusts to 40 mph
January 30th 2023: one night at 18F(-7.8C), daytime highs above freezing. No significant wind.
February 22nd to 25th 2023:
Two nights at 18F(-7.8C) 36 consecutive hours below freezing.
Sustained winds of 15-20 mph with gusts to 35 mph.
Here are my observations for my unprotected in the ground Citrus:
Undamaged citrus with less than 20% defoliation (the winds ripped a lot of leaves off the trees.)
Large Yuzu on Flying Dragon (FD) rootstock from One Green World (OGW) nursery in exposed area
'Sudachi-Yuzu hybrid' on FD rootstock from OGW nursery partially wind protected
Sudachi from Mackenzie farms on Poncirus Trifoliate (PT) rootstock partially wind sheltered
Ichang lemon on PT rootstock from Rolling River nursery, partially wind sheltered
Kabosu from Mackenzie farms on FD rootstock, partially wind sheltered
Kabosu from Mackenzie farms on PT rootstock, partially wind sheltered.
Morton Citrange from OGW nursery on FD rootstock, partially wind sheltered.
large Prague Citsuma on unknown rootstock from Mackenzie farms, wind exposed. 100% defoliated, undamaged
Prague Citsuma on FD rootstock, partially wind sheltered. 100% defoliated, undamaged
Small seed grown Changsha tangerine on FD rootstock, protected by styrofoam box.
Large seed grown Yuzu on its own roots
Some damage:
Prague Citsuma on its own roots, 5% small twig damage. 100% defoliated.
Large seed grown Thomasville Citrangequat on PT rootstock, 5% small twig death
Severely or mortally damaged:
small Keraji Mandarin on FD rootstock, protected by styrofoam box--Dead.
medium sized Keraji on unknown rootstock from Mackenzie farms--60% damaged, completely defoliated.
large Thomasville Citrangequat from Mackenzi farms on FD rootstock, wind exposed: 30% defoliation, 30% small twig death.
the same medium sized seed grown Thomasville as above, but on own roots, 100% defoliated, 50% small twig death. This is one of two survivors from a 10F(-12.2C) event in 2013 and has been killed the ground a couple times, but regrown from the roots.
large seed grown Changsha on FD rootstock, wind sheltered, 6ft from west side of house. No 𝘪𝘯𝘪𝘵𝘪𝘢𝘭 damage, but later I noticed a large bark split 30% up from the base of the tree that impacted the growth above the split. Apparently the proximity to the heat of the house caused premature emergence from dormancy in late February, resulting in freezing of the sap and the resultant split. This is important for this past winters result. This tree is the sole survivor of 24 seedlings after four nights near 10F in 2009, and has survived 8F (-13.3C) event in January 2017 with minimal damage, so the bark split was a surprise.
A couple comments:
The Prague Citsuma appears to be semi-deciduous, losing much of its leaves in a warm winter, so 100% defoliation is not surprising.
Clearly Citrangequats, Changsha tangerines and Keraji Mandarins are not nearly as hardy as the Yuzu and its relatives; what used to be called Ichandrins, though there appears to be some debate on the ancestry. I will continue to call them Ichandrins, for now.
Clearly the high winds were the major death factor here, for the three citrus varieties that showed damage have easily survived 18F with no damage at all in previous winters.
Winter of 2023 to 2024:
One arctic event without high winds at my location, though the Portland and Pearson airports had some, and thus warmer temperatures. Without atmospheric mixing caused by the wind, my location was colder than either airport.
My temperatures: lowest temperature: 12.2F(-11C)
120 consecutive hours below freezing
51 consecutive hours between 15F and 21F
a true arctic event comparable to three previous ones I've had.
This is about 3F colder than what Puget Sound area seems to have got, likely due to extra cold filtering in from the Columbia River Gorge.
Citrus with less than 5% damage and less than 30% defoliation. These are the same as above, but I'm omitting references to their origin and exposure for brevity:
Large Sudachi on PT rootstock
large Ichang Lemon on PT rootstock
large Morton Citrange on FD rootstock
Prague Citsuma on unknown rootstock (100% defoliation)
small Prague Citsuma on FD rootstock (100% defoliation)
Seedling Citrangequat on PT rootstock-one large late growth watershoot shows 30% death, no other damage.
Large seed grown Yuzu on its own roots.
Citrus with some damage:
small Prague Citsuma on its own roots: 100% defoliation, about 15% small twig death.
Large Yuzu on FD rootstock: 70% defoliation, about 10% small twig damage. This is similar to what it has seen in three earlier events of similar or colder severity.
large Thomasville Citrangequat on FD rootstock: 30% defoliation, 20% small twig damage. This is less than last winter!
small seed grown Citrangequat on own roots: 30% defoliation, 20% small twig damage. Also less than last year! Apparently high winds have the same effect as 6 degrees lower temperatures.
small seed grown Changsa on FD rootstock, unprotected this year: second growth flush dead, earlier growth undamaged, with about 50% defoliation. It appears to be hardier than the Citrangequats.
large Kabosu on PT rootstock: 40% defoliation, 15% small twig damage.
small Kabosu on FD rootstock: 40% defoliation, 10% small twig damage...but, there are some dead spots on larger branches that bear watching.
Large or mortal damage:
'Sudachi-Yuzu hybrid' from OGW appears to be dead, though perhaps some small green patches may survive.
Medium Keraji Mandarin: Dead
Large seed grown Changsha on FD rootstock: everything above the large bark split reported above is dead or severely damaged; everything below has less than 10% small twig death.
A couple comments:
It appears that high winds at 18F can cause more damage than calm winds 6-8 degrees colder for longer durations.
It appears that planting a tree near a house for extra protection is a bad idea, since the heat of the house can cause premature breaking of dormancy, leaving it susceptible to a late freeze.
The death of the 'Sudachi-Yuzu hybrid' from One Green World nursery is a real shocker, since it survived the previous winter undamaged, and the fruit and leaves appear to be identical in every way to the Suchachi from Mackenzie Farms. Perhaps it's a different, more susceptible, cultivar? Or perhaps there was some other factor at play that I can't identify.
I was pleased to find that the Kabosu is almost as hardy as the other Ichandrins. (Yes, I will use it the term.) I haven't seen any other reference to its potential hardiness anywhere else, so perhaps this is new knowledge. Might be useful for breeding.
Changshas in general are not as hardy as the one I have, since mine was the result of a mass selection; the sole survivor after exposure of 24 seedlings to four nights near 10F back in 2009. As I said, it survived 8F, whereas another random Changsha succumbed to the same event.
Ichandrins may be more suitable than most other citrus to the climate of the Pacific Northwest, although the Morton Citrange held up pretty well.
Citrus on their own roots don't seem to do as well as ones on PT or FD rootstock.
On a sad note, I have several Satsumas protected in shelters with Christmas tree lights. It seem that half the lights in one of the strings on the Xie Shan Satsuma burned out without my noticing it ( I only checked for the glow, not the intensity) and is severely damaged, though it looks like it will survive.
Jim
