Marj, in my opinion you would be at more of risk if you brought you plant inside the house. Based on the temperatures you stated I would keep doing what you did last year. Keep in mind that you can get ground frost in the mid 30's.
What I don't know how sensitive the Buddha's hand is to below freezing temperatures. I keep most of my potted citrus in my garage where it doesn't freeze- generally between 38 to 50 degrees November through February.
And they all do fine (so far )

Greg

Buddha's hand is very frost sensitive. You will get damage with almost any frost at all.

I'm thinking maybe I should set my plants that are in plastic pots, on something that gets them off the cold concrete floor. That way maybe the soil will not stress the tree. Maybe a flat board?

You can use styrofoam insulation or use wooden slats to keep the pots up off the concrete, I did this last winter, it helped.

Hey, I think I have some of that stuff out in the barn. Thanks Buzz!

After reading this post and others I bought a meat thermometer. It is digital and has a large range. It is telling me my soil is 76 degrees and my apartment is 77 degrees. I thought one of the forums stated that the roots are generally 10 degress colder than the room temp. I wonder if i got junk thermometer but it seems to be acurate. My tree is in those black containers from the nursery. Or did I buy the wrong thing?

Fill 3/4 of a glass with ice cubes and then top off with clean water. Wait 3 minutes, stir, then wait another 3 minutes and stir for one minute. Get the reading with your thermometer. If the temperature reading is around 32 deg F, then your thermometer has passed one test. You can also read temperature of boiling drinking water on a clean pot. The temperature should read 212.


The thermometer that is good to use should have a reading of 0 deg F up to 130 deg F, narrower still if you know what your normal range of temperature for the entire year.

My favorite thermometer is the one I use for fishing. It's range is from 30 deg F to 120 deg F, and it is enclosed in an outer tube that serve as a buffer. I lower it to various depths, let it stay there for 10 minutes, then bring it up to read, the outer tube serve as a buffer and the temperature reading doesn't change as quickly for that purpose, so reading it within a minute, I'll get to know the temperature of various water depths accurately. The outer tube would serve as a running average buffer. If I want instantaneous reading, I take it out of the tube. I use it to cross check the forecast, and have calibrated the weather forecasts too, and I know the difference between the news temperature and ours, so I just watch the news now and it gives me an idea of how cold or hot will it really be in my yard.

Temperature of potting media will try to equilibriate with that of the ambient air (sensible heat transfer) plus the radiation load (if sun hitting it) will try to heat the pot while the evaporation will cool it, and if you let it stay long enough in the sun for example, the pot temperature could be hotter than the air. So you could have a range of temperature difference. If you graph them through time, you will know that the temperature of the potting media would show a lag time and a more attenuated effect compared to the temperature fluctuation of the ambient air.

Joereal
so I did the test and it didn't pass. It read 35-36 degrees in the ice water and 203 when the water boiled. So I guess I did not get a very good thermometer. Thank you for your help. I wonder if it makes a diffrence that it is a meat thermometer but I just couldn't see that being the problem.

Cedar City, UT is somewhere around 5800-5900ft in elevation so the average boiling temperature should be somwhere around 201F but, as Helix said, the boiling temperature can vary by one or two degrees depending on the air pressure. Melting temperature is only minimally affected by air pressure.

I also found out that the boiling temp here is 201 but the freezing temp does not change. And I did the freeze temp test and my temp read between 35-36. I talked to someone that has a lot of education in thermometers and other things like it and he told me that the meat thermometer is meant to be more acurate at hight temps and that there is a graph I can do to see how far off the thermometer is at certain temps. He also said that glass thermometers are the most acurate. I don't feel like breaking anything so I just might put up with the one I have, although he did give suggestions as to other places to look for a digital thermometer that might be better.

I don't mean to disrespect the valuable and obviously knowledgeable advice of those above, but your thermometer absolutely sounds close enough to me. What's a couple F degrees, really. I'd use it.... because as you become your own expert with your micro-environment and tree, your thermometer will be used for relative readings anyway. You'll learn how well (or not) your tree is doing at the temps it reads. Certainly the boiling test should give you a sense of confidence for now.

A bad therm can be one that reads differently each time and IME (once) it was showing crazy readings -- like 20F off between reads. Or if you "jiggled it" it would act differently. That sort of thing.

EDIT: why do I keep spelling "adviCe" with an S instead of C. someone tell me

I didn't wanna make a new thread, so I thought I'd ask here. I hope someone can offer advice.

This is the first year I'll have more than one citrus and I'm unsure as to what to do. For the last 2 years I've overwintered a Calamondin in front of a large southern window in our living room, which stays at around 65. It had a lot of leaf drop but ripened 30 or so fruit from December - February. But now I have a whole bunch of different citrus varieties. I'll be keeping them in the same place as I did the Calamondin. It gets roughly 8 hours of light in the winter. Probably 5 indirect and 3 direct. Would it be better for me to try and treat WLD by keeping the top of the tree cool along with the roots or should I try and heat the root zone up? The easiest method for me would be to heat the root zone up with some Christmas lights. It's our living room so I won't be able to use supplemental lighting.

I have something to ask .

A citrus tree is on stand-by under and over those limits but not all the trees are the same , I can not say that Meyer or Lime will act the same way on their own roots like when they are grafted on trifoliata , am I right ? As i know trifoliata can withstand much lower temerature , and probably he does have another limits .

Thanks

danero2004, yes each tree will have different "extremes" it can and can not tolerate but these general guidelines set are given for "optimal growth" range or "optimal fruiting" etc... the time a tree needs winterization can vary from variety to variety. these guidelines were set down for general purpose. as all trees will respond with in the given temps, light etc according to what you want from your tree.. though one tree will survive @ 45*f the same temp will kill another.. This thread is to address basics of what a tree needs to perform as the owner wishes over a given winter..

CraigMF, From what I remember from all the conversations about root zone temps so long as you do not go above the 70*f heating the root zone to bump root activity is best and not the canopy. The canopy will naturally increase and decrease with sun light.. but roots that do not get sun light do not get the benefit of the warmth and little wake up to provide what the canopy needs as it wakes up from cool nights sleep. Thus you get WLD when the roots are still asleep for the night and the leaves have woke up and want breakfast..
Think of it like this.. in it’s natural setting (ground some where in Fl or Ca) the roots are kept at a slightly higher temp over night ready for breakfast in the am when sun comes up.. the ground (unlike potted soil) has a bit of natural insulation keeping it warmer over night.. it warms up over the day and keeps that heat over night..

Just my thoughts on the matters.. I’m sure If any adjustments are needed someone will chime in..
Gina BabyBlue