The tree is in the ground. The oranges are basically ripe, but we wanted to keep them on the tree for another month or so. Will reevaluate, and if we can't wrap it enough to prevent freezing, will probably pick them. We saw one neighbor doing quite a bit of harvesting today.

I could be wrong; but I don't think oranges (the fruit) will freeze at 30F. I would just throw a blanket or plastic over it to be safe.

edweather Z Let us know how your fruit fair with 30* temps.

I've got 2 sheets over it, and an incandescent 60w bulb under it. We also have a small grapefriut tree, and I threw a couple of tarps over it. Will post the results. Looks like 2 cold nights and then we're good for a while. Also have a bunch of pineapples in 5 gal buckets, and just threw a sheet over them.

We hit 28 degrees for about an hour here one night a couple of weeks ago, and my Satsumas came through with very little freeze damage (maybe 5% of the fruit are showing some freeze damage as of yesterday).

Ripe oranges have a Brix rating of 15-20%, studies show that 15% Brix rated fruit juice freeze at about 29 degrees F, it of course takes time for the fruit to match outdoor air temperature.

Very good information. Never thought of the sugar content lowering the freeze temp.

For those that are interested here is a more technical write up https://www.researchgate.net/publication/241086280_Estimation_of_the_freezing_point_of_concentrated_fruit_juices_for_application_in_freeze_concentration

Though this study does use pear, apple, and peach juices, citrus should be similar as the results show they all act about the same up until about 20% Brix, at which point they start to diverge due to the different ratios of types of sugars in each fruit.

Think we did ok last night. Temps got to 31 briefly, and was 32 for a few hours. Not too bad. Will do it again tonight, and then we should be good for a while. Thanks. Was probably a bit chillier up in 8a, right @Denise? :-)

I have about 40 varieties outside in my northern CA garden. We regularly get down to about 30 degrees but only at night. At that temperature my mandarin and orange trees show zero fruit damage. Of note the length of time at 30 degrees is also very important. Several hours at 30 degrees is very different than several days of consistent 30 degree temperatures. I only see fruit damage when it gets below 28 degrees and even around that temperature it is pretty mild.

-Brett

edweather Z Actually when my Owari mandarins froze, it was when I was living in Sacramento, CA, way back in the early 80's. I was very ignorant then about freezing weather. I figured my tree and fruit was safe as long as it was under a patio covering. I checked my tree and it was perfectly fine, but the fruit was solid as a rock.