How to overwinter potted Poncirus

[tedburn]

Hello Citrus Experts,
I have some smaller Poncirus in pots which I want to take as rootstock for grafting next year.
The pot diameters are about 8 cm in diameter and the plants are about 20 to 30 cm high.
Now I ask me if they loose hardiness if I overwinter them in my greenhause which I keep
between 0 and 1 Degree Celsius (32 and 33,8 degree Fahrenheit).
Otherwise I fear that the roots of the Poncirus get freeze damaged if I let them unprotected on my veranda.
Similar question concerning some potted cold hardy plants as Thomasville, Bloomsweet, Ichang Lemon and Changsha mandarin with pot diameter about 15 cm and hights of about 50cm, which I want to plant in ground next early summer. Do they loose hardiness if they go to the greenhouse in Winter ?
Currently they still stand beside the greenhouse with fleece protection.
Thanks for your experiences.
Best regards Frank

[Ilya11]

It will be difficult to keep greenhouse at around 0°C all over the winter. At temperatures higher  than 12C it starts vegetation and can be damaged by sudden temperature drop. 
Poncirus is hardy up to -24C; it should be completely resistant in your climate if you put your pot in ground close to greenhouse.

[tedburn]

Hello Ilya,
thats a very good Idea and even easy to do, due to my greenhouse is situated on my garage roof which is flat and I have
it covered with an mix of earth and lava stones so it' s easy to integrate the pots.
You are right concerning the temperatures, I guess I haven' t expressed me properly, because I meant keeping 0 degree as lowest temperature.
Yes during day there are fast temperatures over 10 degrees in the greenhouse with light sun.
I think this should also be a proper solution for potted bloomsweet and Co, in combination with a heating cable for very cold temps.
Thank you very much best regards
Frank

[Citradia]

I’ve lost potted poncirus before to zero degrees F outside. In ground poncirus no problem at those temps. I have potted poncirus outside now and don’t plan to throw them into greenhouses unless predicted prolonged freeze in single digits or lower. My potted poncirus hybrids and potted Ichang lemons however, are put in same greenhouses as my satsumas over winter until I plan to plant in ground in late spring. They just don’t have the same cold hardiness as poncirus. I’ve lost citranges and citrumelo with an overnight 14 degrees F in March after they started putting on an inch of new growth, but poncirus only lost the new growth but no wood. I only heat greenhouses when temps are predicted to go below freezing and with small heater it still gets below freezing in greenhouses sometimes but not cold enough to kill satsumas, so I keep citrus dormant in winter but try to avoid severe low temperatures.

[tedburn]

Thanks Citradia for your experiences.
I like very much the really huge experience in this Forum.
 I have the issue, that I have also Cactus and Pomelo in my Greenhouse, so I can' t go under
0 Grad Celsius.
But for my poncirus I will now use the fleece beside my greenhouse, see picture, and dig them in ground ( Ilyas advice).
Under the fleece I also will overwinter my potted Bloomsweet and Thomasville which I want to plant in ground next year, after having made grafts for security. I think Bloomsweet is in my zone 7 very risky and will need winter protection and heating cable.
Best regards
Frank

[lebmung]

I have PT in small pots. I don't do anything. If it's very cold it's probably after snowing. So they are covered with snow.
If under - 15C I would put a blanket on them.
Of course  every climate is different, if you get up and down temperatures they might die. Say this week +10 next week - 15C.

[tedburn]

Hello Lebmung,
thanks for your experience, now I have a very good information with all the experiences and tips and I feel confirmed and safe with my strategy with pots in my lava soil and a fleece cover, thank , you all. Best Regards Frank.

[911311]

Poncirus does not require any care even when inpot. It will make it through winter easily without any attention unless you live in a region lower than zone 5.

[tedburn]

Thank you, I have one in ground since a few years no protection, no problems, but I wasn' t sure with my small ones in small pots.