Hi all,
Great site, been reading lots over the last few weeks.
My question is: what is the best way for me to care for my citrus trees in Ontario over the winter? I currently have a Satsuma and a Valencia in my basement under grow lights. I am going to pick up a few more trees this weekend and will soon need a better solution. There is space in my basement but it gets kind of cool and more so its not very humid at all. So should I try to control the conditions in my basement or would a heated greenhouse out back be better? What does everyone here use for a greenhouse solution in colder winter climates?

Welcome to the forum! I can't help much from an experience in really cold climates, but from what I have read on these forums, your basement should be OK. In fact there are some I have read about that store citrus in a basement for the winter with no added light. They just go dormant.

I only have key limes in containers and bring them in when the temperature is going to be close to or below freezing-- then I put them in my unheated shop for a few days at most.

Mintchris,

I am new to citrus, but I have my few trees in my unheated third floor, which has seen temps in the low 40's so far this winter. I built an enclosure out of PVC pipe for supports and draped it with old clear shower curtain liners to minimize drafts, which I was worried about up there. I have fluorescent lights on a timer for added light (there is one small south facing window nearby), and have the roots of the trees warmed with Christmas lights. My trees are currently experiencing their first flush since late summer/early fall. Inside the enclosure, with the Christmas lights adding heat, the temperature has gone down as low as 50 deg F. The humidity is a problem, it has not gotten above 50%, and it seems that is only when I am in there breathing and watering! The enclosure is only big enough to house a 3ft X 5ft table and room for me to walk down the length and width of the table. The actual frame is 4ft X 6ft X 6ft high.

Our basement is used as my husband's wood shop, so I was concerned that it would get too dusty down there, even with the enclosure. I hope this gives you some ideas or at least a good chuckle! Best regards, Barbara

My trees are in an unheated room with large south facing windows where lows have dipped into the high single digits celsius.

Thanks everyone for the replies. I guess I was concerned since I havent seen any growth since early fall. What helps bring about new growth over the winter? Should I be keeping the roots warm (how)? Higher humidity? What is the min outside temp that people usually put their plants back out for the summer?
Thanks again!

One thing you want to do is keep the plants off the cold basement floor. Try putting them on a piece of 2x8 cut lumber. Then you can wrap the pots with Christmas lights to raise the root temps.

Get yourself a $10 digital kitchen thermometer that goes down to at least 10 deg F. The kind that has a 4-5 inch probe so that you can monitor the root zone. They usually also go up to standard cooking temperatures, too, but you don't want one that is only above 100 deg F. Christmas lights can cause your soil temperature to rise higher than you might imagine, so keep an eye on the temps and modify the number of wraps per pot if you find you need more or less heat. I target 65-70 deg F, but I believe up to 80 deg F is ideal for good root activity. One 40 watt string may do that for you if you only have a few trees. Good luck, Barbara

If you want growth during the winter then you have to heat the roots like Barbara suggested. Roots are essentially inactive below 60 F.

Your tree will survive just fine in the basement without heat and light, but it will not grow without heat. If you heat the roots, you also need to provide light or the tree will become very leggy. Also be careful when you begin to put it outside in the spring as it will be subject to sunburn, especially if it has been growing under lights.

You may also want to know that to get your tree to bloom, you need to expose it to about 800 chill hours (below mid 60s).

Basically, if you desire year around growth for your trees, than you have to change the conditions that prevail during the winter months, to be the same as they are during the summer months. Three years ago I planted a Marisol Clementine in the ground in my Colorado greenhouse. During the winter, I maintained the soil temperature of the tree's root zone between 75-80F by using two heating pads. I also surrounded the tree with aluminumized reflectors and nightly lighted the tree with a Halide light. I maintained the lighting every evening from sun set until 10:00 PM. Further, I removed all blossom for the first three years, so that the tree would achieve the greatest possible growth. I did this ever day and night for the last three years. Lastly, I fertilize the tree year around (summer, fall, winter and spring). By doing so the tree produced five (5) growth flushes every year. The night air temperature in the greenhouse is maintained between 51-57F from November until January. This is to supply enough low temperature stress hours to insure a good bloom on all of my trees. The day temperatures are normally between 70-80F depending on the weather outside. The tree is now 3 years and 1 month old. It stands at 6-1/2 feet tall and 6-ft wide. Presently it is just beginning a new flush (called the spring flush), and I can see thousand of small round blossoms developing. I am going to let the tree produce fruit this year for the first time. I plan to "pollinate" the flowers using gibberellic acid. If you have the desire, you can also provide this level of cultivation in your basement. A picture of this tree's first two years of growth can be seen in the greenhouse section of this forum. I will post a picture of the tree this year after the tree has set it first crop. Take care and good lock to you and your trees. - Millet.

Thanks for all the info everyone. I tried the christmas lights but the pots are kind of big and I dont think its working too well. Are there any other really good ways to bring the soil temp up?
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One very common method is by setting them on heating mats. Better yet, you could do a combination of heating mats and Christmas Lights. - Millet

Thanks again for all the help!!
What kind of heating mats work the best? Can they be run all day with no risk of fire or should they be cycled on and off?
BTW, I went out this weekend and picked up a red navel, ruby grapefruit and big meyer lemon tree. All in full bloom so my house smells fantastic!!

Thanks.
I got them from Humber Nurseries in Toronto. They are just above the airport maybe 10 minutes by car. They had a really great selecttion actually. Tons of Meyers, different limes, lemons, oranges, grapefruit, tangerines, etc. Lots of other tropicals too. If you call, there is a woman, I think her name was Robyn in the tropical house who knew her stuff and will help you out. I am not sure if they do mail order or not, I think they are just a regular retail nursery but you never know. Its a good find here since I didnt think anyone in Canada had the selection they do.

Thanks. I'm always interested in new sources for citrus in Canada. Their website is here.