Citrus greenhouse overwintering question

[Plantinyum]

Hello , I have two pomello's from which one is a seedling , the other is grafted onto flying dragon rootstock. Have also a mandarin, two unknown lemons and one kumkuat grafted onto flying dragon. I have a unheated greenhouse I which I thought to winter them, but in the day the temp inside gets to 35C and sometimes above. The nights are cool and this amplitude worries me a little, will they be okey? In the coldest times I will take them in my basement ,and when warmer will be putting them out. Will it be too hot for them in a sunny day, I can just open the doors and windows to cool them up, and close them one our before sunset to generate some heat for the night...thanks for any replies.

[brian]

I recommend checking the soil temperate of the trees on a sunny day follwing a cold night.  If the soil is quite cold but the air is warm and sunny you may have issues with leaf drop. 

I overwinter many citrus trees in containers in my greenhouse, but I have it heated to minimum 55F/12C.  It also gets hot like yours on sunny days, but the soil is never cold enough for the roots to become dormant.

[Millet]

I 2nd Brian's instructions.

[lebmung]

Similar to your zone. I keep my citrus only above freezing level. Once it starts to get really cold, I don't expose them to warm temperatures anymore. Soil and air temperature ranges from 2 to 10 C for two months with not much light.  No leaf drop.
The most important part is watering. As long as the soil gets dry there will be no issues. Also if the humidity is high. I don't water them at all for weeks. I don't use fast draining soil for PT or FD rootstocks, but a mixture which holds water for longer time.

[Plantinyum]

The greenhouse has a mortar base, which is isolated and is deep into the soil, the soil in the greenhouse is isolated from the outside soil. I am thinking if making hols in the soil for the pots, burry the whole pot into the soil to regulate its temp, and just open the greenhouse while sunny , to not get so hot inside.

I have not watered them for around a month, the soil in their pots is moist, I will keep them on the dryer side.


What's the lowest temp they could handle, I know the rootstocks give some hardiness to, and that the lemons might be more cold sensitive. In the nursery I bought the grafted  pomello and kumquat from, one of the employees said they keep them in the greenhouse without aditional warmth, and that the citruses were handling temps around minus 6-7 C.

[lebmung]

The greenhouse has a mortar base, which is isolated and is deep into the soil, the soil in the greenhouse is isolated from the outside soil. I am thinking if making hols in the soil for the pots, burry the whole pot into the soil to regulate its temp, and just open the greenhouse while sunny , to not get so hot inside.

I have not watered them for around a month, the soil in their pots is moist, I will keep them on the dryer side.


What's the lowest temp they could handle, I know the rootstocks give some hardiness to, and that the lemons might be more cold sensitive. In the nursery I bought the grafted  pomello and kumquat from, one of the employees said they keep them in the greenhouse without additional warmth, and that the citruses were handling temps around minus 6-7 C.

Aerating the greenhouse daily will reduce the humidity and mold issues. There are many citruses so it depends on each how much cold they can get. Just keep the greenhouse over freezing level. Plants are not dormant like in outside. Over the years plants will adapt to cold. However if you get a citrus from southern Italy or Greece it will not survive like a tree grown from seed and grafted when young in a cold climate.