As its that time of year again here when we all start to think about bringing our plants in. I thought I would start a post on my Winter tactics to keep my citrus trees alive. Its a new experiment this year. Firstly, because its now in a pot far to large to bring inside each winter and I want to grow it bigger to get more fruit. The root stock temp target is 7C+ but ideally 10C+ will ensure a better chance of avoiding leaf drop. Average UK temps in london: These will be less outside of london so keeping that in mind grow house lows should be similar. These trees are in a PVC grow house to begin with but temperatures still drop very low in these during the winter and extra measure are needed to protect citrus trees. 4 to 7C needs to be gained to keep the trees alive. Lemon Tree Natural Growing Climate Data: METHOD: I've started by placing canes around the tree and using a mini greenhouse cover created a greenhouse within a green house for the small citrus tree. this should gain a degree or two during the night on top of the slight temperature increase of the larger grow house. Large (I use black for heat absobstion) pots of soil hold temperature from the day for some hours but once its left the soil it will take equally long to regain heat. This is when the damage is done and trees die. I've tried to combat this by insulating the pot with fleese and then also the greenhouse cover both with clear bubble wrap. This should maintain the heat for a good amount of time opposed to being open to the elements. My grow house just isnt practical to also insulate but this method may work with just the mini greenhouse cover which can be purchased on eBay. If it works for you post below. I'm thinking about getting a temperature probe and watching how this performs. The older the trees become the more hardy they will be but as they don't go dormant due to there natural climate there is always the risk of a tree dying over winter even when with precautions. Are there any methods other cold climate growers use? Please share photos, methods ect for outdoor citrus.
I don't have to deal with this issue as my trees are indoors year-round but I do have some thoughts on the matter. Leaves are shed as they attempt to photosynthesize while the tree's roots are unable to provide the moisture necessary to cool them. This happens as root activity slows in cold temperatures and stops completely at 13C. Then it seems there are two options: Keep the roots warm and allow the tree to remain active or allow the roots to remain dormant and keep the tree in the dark. The following post shows how the former can be done by employing some incandescent lights: In-ground Bearss Lime in South Surrey. In your case the lights can be wrapped around the container thus warming the soil and roots. Is your tree a Meyer lemon? That variety is hardier than your average lemon.
I have read this before, but only shaded areas were suggested for inside the home to help in the colder months as the lower temperature for the trees studied could have been due to reduced lighting at the colder times. The moisture absorbed reduces the colder the trees become as does the amount light they could tolerate before leaf drop. (Attached is a pdf document of a lemon study I found no need to exsperiment). I think I will have to reduce the light it receives around december time. I believe this is a 'Citrus Limon' or a 'Citrus x Lemon' zone 8/9 to 11 similar to the Meyer but of slight warmer climate.
Its about 6C in the tunnel right now and the probe inside the roots is showing about 18C even if it drops to -5C I think the tree will be ok temperature wise. However after the irrigation accident that had nearly filled the pot with water... I should try avoid any more mistakes. Its been temporarily repotted as the night was moving in.
