I believe you will find that a large percentage of us feel that warm soil is not only unnecessary, but unnatural...considering that these plants do just fine when planted outside in more moderate climates.

If your plants aren't doing well in the winter, you may want to investigate other reasons such as humidity and light levels, watering routine, etc.

You are absolutely right, by the way, in thinking that wrapping the heating cables around the pot won't quite accomplish what you wish. Plus, the heating cables that I've used extensively in my seed germination flats, have directions that specifies that you do NOT cross the cables over itself.

Right off the top of my head, I can't think of a reasonable way of just heating the soil inside the pot that would be safe!

From my experience, since I too live in the North East, cooler room temps and cooler soil temps are much more preferred for my citrus...Unless you can grow them in a greenhouse where they can get tons of sunlight for hours, I wouldn't do it..

If you heat your pots up, be prepared for a massive amount of leaf drop, spindly new growth and a host of spider mites or some other pest. The they will demand high fertilizer demand, more humidity, and definately a high amount of sun light...
You have to meet these demands, if you are going to warm your roots ups..

If you want to rest easy and see your citrus stay green all winter without dramatic leaf drop, with lots of blooms, to go along with the amount of sun light we get this time of year, then keep the roots as cool as you can go in your plant room.

Cooler roots=less sunlight, warmer roots =more sunlight

Trust me if you take the unatural course considering these plants do just fine in conditions as rhizzo explained, then you will be asking for a host of problems..Been there, done that..

Don't forget, if you go the cooler route, you will be required to let the soil dry out between waterings..

Good luck

Mike..:-)

That's different than my experience...but I can keep it in mind.

I think the concern is more based on wide daily variations that come from being in a pot vs. being in-ground.

That's different than my experience...but I can keep it in mind.

Hairmetal: I know you came here asking the questions, but would you care to share your experience with keeping Citrus roots warm during winter? I'd like to hear it.

Well...I used to grow a Trovita Orange and Oroblanco grapefruit (some say it's a pummelo) under a HID light in my basement at my old house in Ohio.

They stood still indoors until I strung Xmas lights on the pots, then they took off. Could have been a coincidence.

I have read that the roots stop growing under 54 degrees.

They died later on from what appears to be a very severe infestation of some scale-like white growth that I just couldn't kick.

The soil temperature in my greenhouse falls to mid 30s in pots and upper 40s in the ground at 4 inches with no ill effects. Don't expect any growth at these temperatures. But growth during the winter is just asking for trouble. Better to let the trees go semi dormant.

My potted citrus hasn't grown since October. Just starting now with daytime highs in 80s. The fruit of navels have been great for a month or more and Chandler pummelo for two months. All with nights in the 30s.

I am 100% with "fruitnut" and others on this..."

"under a HID light in my basement at my old house in Ohio". is what you quoted...

That was my point when I said....Warm root temps=more light.

I have had great experiences with active growth too, with warm roots on my citrus year after year till my electric bill shot through the roof and forced winter growth caused a host of problems, mostly too much weak new growth loaded with partying spider mites..

Personally, I would rather do as '"fruitnut" suggested and deal with no pests, no high fertilizer requirements, no dropping leaves, and for sure no darned pests...This year has been the best year ever listening to some of the pro's here at keeping my citrus cooler than before..

I would rather have them not grow, and rest, stay healthy and full of green leaves and flowers...Don't even have to be watering them so often..Less work for me.

Good luck...:-)

What about light then - would supplemental light be needed in a Maryland winter, under the reduction of greenhouse framing and glazing?

Assuming I keep the GH at low 60s during the day and mid 40s at night...

However, I also want to try bananas who are more in need of heat...and light...but I also hear the warm soil is MUCH more important for bananas. So a balance will be needed.

My concern is based on what a greenhouser in Ohio told me once...that they can only ripen lemon and lime, that grapefruit, orange, and mandarin just can't handle the low light levels or cold soils in winter even in the GH (in OH) - our winter sunlight in MD is better but not by a whole lot.

I really really really love mandarins and hope to successfully fruit them.

FWIW I don't own a GH yet, but I'm just trying to get my ducks in a row to try and do it.