I have no doubt that there are citrus that can reliably live and fruit in zone 8a.
Despite the fact that most “cold hard” ones aren’t sweet, I’ve been looking for a truly hardy citrus for a long time, but hardy is a little daring, what’s cold to some isn’t so cold to others.
I have a small collection of “cold hardy” citrus and poncirus hybrids myself. time will tell how hard they are in the cold.
but from what I’ve found out, most hybrids are hardy to a maximum of -15-18C and have this unpleasant poncerin (turpentine/resin, don’t know how to describe it) taste
and that there have been so many attempts to breed a cold-hard citrus with poncirus, I thought of going other ways, such as breeding out the poncerin and related substances, so that at least one can do back crossings with poncirus. It’s not just sour, it’s resin/turpentine…like
if you can breed sugar beet from 1% “sugar” to 20%, you could also reduce the poncerin and increase any existing sweetness to 200%.
but i won’t die for this argument, it’s an idea,
Check out this accession in the USDA collection. It is believed to be a chimera between trifoliate and satsuma with the leaves being trifoliate and the fruit more like satsuma. No mention of hardiness, but is anyone growing this? I imagine if the fruit look more like satsuma then there’s a good chance the flavor is more like satsuma too since that’s the part of the chimera more dominantly expressing in the fruit.
Here is an un-named selection that produces monoembryonic seeds (most of the C. trifoliata produce polyembryonic seeds). Monoembryonic Citrus are good for breeding because their seeds do not simply produce clones of the mother tree.
I have Citsuma Prague. But there were solid arguments why it should be not more cold hardy, it is partiell poncirus and satsuma genetically, why should the satsuma genetic part be more cold hardy…
There was something that it makes more cold hardy, but I can‘t find the link to explain it reasonable.
Not all parts of genetic is equal less cold hardy, intimate metabolism… or something, and personal experience shows it is a bit more cold hardy…
I think 10-15 degrees is a good rule of thumb for plants protected with plenty of lights and a tucked-in fabric cover. In Dec I had an outdoor low of 7F for 2 days. The max/min thermometer underneath covering read 26F during that time.
My set-up had a polycarbonate top since I was afraid the weight of wet snow might rip off loquat leaves. The polycarbonate probably gave a few extra degrees.
Most Citrus are not sweet. Most of the sweetness genes come from Citrus reticulata and Mandarin Orange and Citrus Maxima Pomelo. But 30 years ago Lemons and Oranges were just as sweet as each other. Oranges are now typically twice as sweet as lemons. Its more the acid levels that render one sweet and the other sour to our preceptions. Lemons being 2-3 ph and oranges 3-4. Grapefruits have 12 calories per OZ and Oranges 14, but GF ph is 3.3.
But I digress. Sugar beets got sweeter not just from selective breading but from chromosome doubling. Citrus are notoriously resistant to chromosome doubling. Not only that they have a long juvenile period up to 20 years to fruit. At least working with Trifoliate is fun because those hybrids can flower in 3 years. You can select citrus for size, flesh and rind but turning on or off the biochemical factories seems to be difficult.
Check out this write up on ‘Dunstan’ citrumelo. I haven’t fruited mine yet, but I have three in ground which have overwintered well repeatedly in 8a with zero protection aside from good drainage.
In the video you can see that yuzu isn’t juicy. I first found out about yuzu while living in Korea. Over there they would make a preserve from chopped up yuzu mixed with sugar & honey (looks a lot like marmalade). Then you would just stir a spoonful of it into hot water. I loved it and will probably use mine this way if I ever manage to get a harvest. I think the low moisture content of the fruit helps to make the preserve more stable/less perishable.
I think yuzu is a good candidate for radiation treatment to reduce seeds like has happened with other citrus, especially since it’s used for juice. I wonder if it’s been tried, or why not
the problem with radiation, you need more than 10 000 plants, and you don’t know which genes are being destroyed, mostly it is random and if it brings any advantage, you cross with that plant, which is mostly very stunted.
Under 1% of the radiated plants are used.
but expecting a desired mutation takes a lot more attempts and luck.
I have a cutting I’ve been rooting for a few months in my greenhouse, it hasn’t died or started growing yet. Does anyone know if they are supposed to root easily? I had gotten it planning to graft, but ended up not having enough rootstocks for all the different scions I got that week, so many of them got stuck in soil instead.
I was able to root a ‘Dunstan’ cutting a few years ago. My success percentage wasn’t high, but I am still rather new to Citrus cutting propagation. From what I’ve read Citrus cuttings root best in the summer time. The only reason I haven’t tried to propagate more is that I want to try the fruit before I go crazy trying to propagate it.
From my research, and experience, and there are variations depending wind chill, and how any hours it stays cold…, but, here is a general idea on cold hardiness:
When grafted to Trifolate rootstock.
Navel Oranges: 25F
Key Lime: 30F
Satsumas: 16-20F
Mandarins: 16-20F
Meyer Lemon: 25F
Trifolate Orange: -10F.
Kumquat: 14-17F
Several hybrids are more cold hardy.
Arctic Frost and Orange frost are hybrids that might can take 12F or so.
After reading reports and getting feedback from Mr Stan, I came to the conclusion that unless i want to protect a true citrus, or grow a sour hybrid, my best bet for Good or decent, more hardy fruit is these: #1) Prague Citsuma: Has survived several 0F to 8F freezes, probably truly hardy to 5F or colder, and has a true mandarin fruit. #2) Ten Degree Tangerine, and is sort of a lemonade fruit: has survived 8F.
Also:
*Changsha, sort of a bland orange: has survived 8F.
*Thomasville Citrangequat: similar to a kumquat, has survived 5F or so.
As far as standard citrus, that need protection, 16F-20F, LSU has released some great Satsumas, and Louisiana Early, as well as Early St Ann, are two real great options that should be more common by now than they are.
This might encourage you on Prague, I am pretty sure it is fully zone 8a hardy, maybe even parts of 7b…
Mr Stan said Prague did fine in the 8F freeze that killed so many of his citrus, satsumas and stuff.
I asked him to compare it to his Carolina Lime and Ten Degree Tangerine, he said Prague should be the most cold hardy of the three, but that all three survived the 8F.
I also joined some European forums and seen people posting pictures of their Prague covered in snow and, several reports are that it survived 0F or 1F or 3F or so with minimal or no damage…
The only negative i have read so far is that it is a slower grower. I plan to test that claim this year by adding manure. I have 3 small Prague plants. If I was in 8a or a warm part of 7b I would plant a grove of these, since when trees get bigger they tend to take more cold. (I used to grow citrus in 8b, and Satsumas I planted up to 22 years ago are big fine unprotected trees. So a mild part of 7b i would try Prague )
@swincher Unlikely, since it is still rare and new here in the USA. Mr Stan has the oldest tree in the USA. He usually has a few small trees each spring that sell quick.
I wish i had dozens more Trifolate rootstock, I would graft out some to trade as well as give sone to family members back down in Louisiana who have Satsuma trees, for them to grow n test Prague. We need to figure a way to spread and promote this tree!
It is very slow grower and also quite ugly tree with small leaves that fall of in the winter like on poncirus.
I wasn’t able to test it’s hardiness since I got it only for 3 years and the minimum was -8C
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