I noticed today my 6ft tall rusk citrange has turned brownish and yellowish and trunk outer bark is split about two inches vertically. I think this winter's prolonged single digit and sub freezing temps have sealed the deal on hardy citrus at my house.

Citradia, very sorry to hear that. Just curious, was your Rusk in full winter sun? Here in Maine I've noticed that when we have our normal deep winter cold following an unusually bit of warm weather that even very hardy native trees like sugar maples and hemlocks can have bark splitting damage on the sunny side of their trunks. For that reason I'm planning to plant all my experimental hardy citrus seedlings at the southern end of a forest opening that gets full summer sun, but full winter shade.

Yes my trees are on south facing slope in full sun. It's a shame we can't grow fruit trees in full sun, which they need to perform well, because of trunk splitting.

Ok. I looked again at my trees today. The rusk still had some green under trunk bark when you scratch it, as does my Thomasville which also looks like it had a run it with a sand blower. The swingle citrumelo still has deep green branches and is still green inside some broken branches. Pretty sure swingle is gonna make it, and hopefully the other two will too. My seedling first year ichangs and dunstans are pretty much toast since their little trunks are exploded and split wide open. This winter has been a true test.

Hopefully the trees will look better as they put out new growth.

Dr. Powell at Petals of the Past nursery grows his citrus in the greenhouse. He explained that citrus are understory trees that do very well in partial shade.

I think you could do well growing your citrus under high pine or similar shade. I noticed in Florida wild citrus were thriving in the woods.

As an experiment I left outside Owari seedlings that had been neglected for two years this winter and it appears they have all survived 15 degrees F, even keeping a few leaves. Part of that reason may be because they had put on almost no growth the previous year, so were very woody.

Yes. I went to petals of the past for the expo last year. Beautiful place. I learned there that if satsumas drop leaf from freezing temps they won't bloom in spring. This confirmed to me that real citrus, not hybrids, need to be in greenhouse where I live, because they can't handle a 24 hour freeze in the single digits or 20's. I have no shade on my property. If citranges which are not grafted and won't bloom until 20 feet high, can't survive my winters unprotected without greenhouse, I won't have them. One of my bloom sweets and croxton were protected this winter with 4 mil plastic domes and heat lamps, but are now completely defoliated and died back to trunk. My trees protected with space heaters with blowing fans are perfectly fine. Greenhouse alone not good enough here; have to use blowing heaters too.

I'm going out on a limb a little bit here but maybe the citrus got too hot under the 4 mil dome with a heat light and got burned. Or maybe the citrus got real happy with the heat and protection and broke dormancy, then the growing leaves got burned by a frost that didn't seem too bad. These are just possibilities. Satsumas can be safe down to 14 F or so if they are dormant. Here in central Alabama we can have 80 degree days and in less than week have a hard freeze. That can be very hard on citrus. Tom

The heat lamps didn't burn the croxton or Bloomsweet trees all winter and no problems noted until I had zero degrees for entire night and didn't get above freezing for weeks. The rusk with split trunk was not burnt until second or third time I got down to 1 degree or less, and only protected with plastic wind break and frost cloth. The first polar vortex it was encased in wire cage full of leaves. I have been covering and uncovering these trees sometimes twice a day according to temp changes all winter to ensure they don't get too hot.

too bad to hear about your Citrus damage/death. It appears your Citrumelo 'swingle' performed the best this winter? If you look close you can see the trunk areas facing the sun are brown while the other areas are still green. I too will modify my protection method to limit the amount of direct sun on the Citrus.

My Citrumelo 'Dustan' looks pretty good with some minor burning (I'm being sarcastic).........Here's a few photos from today. I'm not confident my Citrumelo will survive....only time will tell. Low in my yard was -21.4C (-6.5F) with many, many, many other cold days/nights.

Brown foliage


Close up


Trunk photo


Thick branch


Another branch

Yup. That's what my stuff looks like.

since there is no growth in winter I would suggest non transparent material for frost-protection. Sun in winter is our worst enemy. At low temperatures it is worth nothing and causes a lot of damage.

I had a Nippon orangequat do the splits a few years ago. My theory is that the young tree hadn't gone into hibernation when we got the 1st freeze event that that year. It split about 3 or 4 inches vertically.
So what I did was wrap a few Zap straps around the wound (not too tight) for a season and it seamed to work fine. There is a bit of a scar but the young tree seems no worse for wear.

I did have them under plastic well before the freeze and perhaps that was the the root of the problem?

Thanks for the post!

Greg

Thanks for the zip strip suggestion. Maybe the green stretchy tape we use to tie up tomatoes will work, and stretch as trunk grows?