yup I am colder
how cold did u get last year...............

with the supplimental heating I might as well go with another satsuma though

Hi Frank,

the lowest I recorded in my yard last winter was -2.9F (-19.3C). That night was the night I lost power from a snow storm...........my luck.........the citrumelo had no supplemental heat that night. I think keeping the wind off the citrumelo really helps a lot with its hardiness.

thanks
I was thinking of just thowing a tarp on it............if it was closed the ground would radiate a bit of heat upward................the ground never freezes with my other citrus enclosures

Frank, that would be interesting to try. I also suspect that cold desiccating winds may play a significant role in hardiness for these up here. If you could keep the wind and rain/snow off of it you might gain a little hardiness.

Along these lines, I've seen a research report, which demonstrated that citrus with dry leaves/wood are slightly more cold tolerant than analogous citrus that had been sprayed with a mister shortly before being exposed to the cold temps. (Note this is different from from micro sprinkler systems that supply a continuous flow of water during freezing temps to protect the trees)

Depending on the rise of temperature within the protective enclosure during the winter, the tree could very easily have developed no hardiness at all. - Millet

Millet, very true, the devil is definitely in the details. I've seen examples of simple enclosures used for palm trees heat up to 90+ F on sunny days in winter.

Frank, if the Citrumelo was sited carefully where it received little direct winter sun and a light colored (white) tarp was used, the potential for overheating should be significantly diminished.
Adding a water barrel (like you do for your other trees, but w/ no aquarium heater) would also probably help reduce the odds of overheating.

thanks
lol I was hoping for minimal work, thinking I should cut down my 6 foot tall meyer that wont flower and plant another one of Stans Satsumas lol

I've been wondering if creating a wall of white overwintering film, like they use on greenhouses to keep plants dormant, might help plants survive that wouldn't quite make it. Pound in posts around the tree and wrap in the white plastic to make a cylinder that keeps the winter wind and sun from getting a direct path at the tree. Top left open to let any warmth leave. Come spring unwrap the plastic and put away until the tree goes dormant the next fall. This way the tree can be planted in a warm full sun location. Probably would also wrap the lower trunk with something to protect the bark from voles. Does anyone do anything like this for other plants, or would it be better to completely wrap the tree? Just trying to figure out a low labor/cost method to get/keep the plants deeply dormant.

I read a study that determined sunlight is required to 'harden off' citrus for winter cold. Citrus kept in the dark under the same conditions were less hardy. I think the sunlight generated sugars in the citrus which made it hardier. I'll post a link to the study when I find it.

Therefore, sun may be required to get that extra hardiness. The only issue is excess heat due to the trapped sunlight in the enclosure.

Here's the link to that study:

http://www.plantphysiol.org/content/64/3/425.full.pdf

Tim, interesting paper, I had not heard of that before. I wonder where they got the idea for that study? I still believe the most important factors for cold hardening of citrus going in to winter are overall tree health and the amount of cool weather (number of hours below ~50F without going below freezing). Also, I'm not sure darkness would have much of an effect on hardening off in any of the winter protection systems we are using. The trees in that study were held in complete darkness, so unless we start wrapping trees in aluminum foil....

Greg, that sounds like an interesting idea, it might be worth trying w/ a Dunstan. However, I would be most worried about heat loss out the top during the odd sub-zero winter night, so I'd probably add a roof and a barrel or two filled with water inside.

fwiw my outdoor citrus get very very little sun from late November to March
plastic, blankets and tarp

I did notice that my cold hardy (10 degree tangerine and thomassville) that explicitaly faced the north had some die off of the north sides, thinking that the slight sun exposure warmed the local volumes enough during the day so that they werent cold for an extended perioid of time

the only die off was on the sides of trees that faced north

Hi Frank,

perhaps by late November the sugars in the citrus have formed......protection in late November may be sufficient in our area.

I tried a single plastic wrap around cylinder of wire fencing with top open to air around newly planted "wonderful" pomegranate last winter and thought I lost it, but it sprouted from base of trunk about a month ago. Also, tried the wind break with plastic idea with an L-shaped plastic wall blocking north and west winds around my trifoliate hybrids and a young Changsha, and thought I lost the Changsha, losing all but the last 5 inches of growth above graft line, and it has only put out about 4 inches of new growth this summer so far. The hybrids were not harmed at all. My Changsha is getting the full roof and sides protection this winter that got my Kimbrough satsuma through last winter without a hitch.

What was your low temp.....you must be in western NC to get killer temps?