Brought the citrus clan out about two weeks ago. Been slightly cooler than normal--still 86 F. a couple of days ago, but then a couple of days stuck in the 50's. Nights have not been much lower than 40 F, but I will leave them out if they are predicting anything down to 32 F. because mine get some radiant heat off a large black-top driveway and off two garages. Extended looks okay--mostly 60's day. Only thing I still have inside is the ultra tropicals--coconuts, etc.,

Hey, Mike, good to see you!

Mine have been in the cold-frame all Winter, which helps protect them from the worst cold.
Evenso, they've gone through many, many nights and days between 30F and 40F degrees.

Josh

Citrus aren't nearly as cold sensitive as some may think, Mike. They are considered SEMI-tropical plants, not full tropicals. You're plants are safe.

If I am hearing this from 3 well respected members in my eyes, then I am feeling much better.

I have never exposed them to such cold temps, but I also know that some are having great success with them at those temps anyway. It did get to 39 degrees this am and they seemed ok. They seemed to have loved the rain even though it was a cold one!

The ones in the clay pots felt a lot colder than the ones in plastic.

I was afraid that the sun was too hot for the leaves to keep up with hydration as the root zone still stayed cold. I have seen the new growth flop over in the early am as the sun gets hotter, but then straighten by mid afternoon as the temps rise into the 60's to keep up with hydration.

I was also concerned because I assumed that root temps drop a whole lot more drastically and warm too rapidly as compared to those in ground where the ground is warmer and keeps the root zone at more stable temps as the air around the plant either gets very cold or hot.

I assumed that in a pot was entirely different than in a tainer therefore more stressfull for the plants.

I apprecaite your ability to help me realx about it, Josh, Rhizzo, and Dave!

Mike

I leave all of my potted citrus outside the entire winter. The lowest temperature they have seen is around 25�F. While there is obviously significant differences in the cold tolerance between different citrus, there shouldn't be any ill effects with temperatures in the high 30s and 40s for most varieties. My mandarins, oranges, meyer lemon and grapefruits in general demonstrate the following approximate cold thresholds: 28-29� (damage to new growth only, old growth completely unaffected), 25-26� (mild damage to old growth at the periphery of the tree, -Brett

My kumquat was left outside over night at 25F with no damage. The pummelo and tangerine had been tried at 30F and were doing fine. But they were placed in front and close to the garage door.

I know exactly how you feel; I've been there before. But you already know (in the back of your mind) it doesn't really matter what we've experienced ;-) Different container sizes, materials, times of year, and the rest of micro-climate influence is too great to be helpful enough to answer your question. Oh yeah, rootstock is kind of important too!

Mike you are correct and worrying about the right things. WLD may not be an issue for just one day, but root-loss is. The soil temp gauge is your best friend in these times. If you determine the container soil temp differential between ambient air temps, it should give you a good idea. If you want to be on the absolute safest side, don't let em get below 55. But IME they can get down as low as 40 and not die... heck I let one get to 35 (which I'll never do again) and it didn't *completely* die.

To answer your question, I've lost orange and mandarin trees on C-32/C-35 rootstock with unprotected plastic 16"-20" containers in the gritty mix when ambient temps went to 28F.

Other *unprotected* citrus trees did fine that year were:
* on Trifoliate rootstock, best overall compared to Citrange and hybrids.
* in over-sized containers, ie. the roots were not grown to the outer container edges.
* in bagged soil, whereas gritty mix suffered more.

I covered the foliage that year, not the containers. Although all the above trees "did fine" they did not thrive with the first growth flush, which should've been the biggest. It took half the growing season for them to act like healthy citrus again. Those which I protected the containers all did excellent and never seemed to languish.

Looking at your trees and the excellent care you provide them, you want to stay around that 50+ range =) It's just not worth the disappointing and frustrating remainder of the year caring for plants that look so much worse than they could. I've done it!

Why not buy some bubble wrap and put it around your trees containers. A lot easier than lugging plants inside. Just watch high-end peak temps ;-) It wraps back up nicely and re-usable.

Hope your trees do great!

Do you think that clay pots provide significantly greater cold protection than plastic in the sense that it takes them longer to cool down?

Cath

That is a good question Cath!

I can tell you this though. When I picked up my clay container verses plastic ones to bring them into a warmer place, the clay ones were COLD! In the morning when the sun starts to hit them, roughly around 10 am when I can feel the heat the sun, the ones in the clay limp verses the ones in the plastic stay firm. I am a bit confused on this.

Here is something else very confusing!

If it is safe to leave plants outside in temps that cold, then how in the world will the mix, especially heavier peaty ones dry out in time if the roots shut down at temps under 55 before they start to rot from an extended period of wet cold mixes?

I hope this can be explained since I have never made it a habit to store my plants at temps below the 50's for reason Cedbury explained, but it is exhausting to bring them all out just to realize I rushed things a bit. That darn 80 degree weather the other day fooled me!

Hopefully someone will see these posts that know. If not, I will try again at the container forum

Mike:-)))0

Thanks Brett,Cebury, and Jlgarden for your thoughts too.

Cebury, I hear what you are saying. For sure I know that COLD temps can have a negative affect on them since I am already noticing the leaves on my Oro bending dowards and looking like they are tired. I don't like it.

If they are reacting adversely to such cold temps, I will let you all know and bring them in asap.

Here is a pic after two days in much colder temps.Looks as if the leaves are not getting hydrated, almost wilting and yet the mix is moist....Not looking very good and it concerns me. Not sure what to do/:-(((( I can't afford to heat the other greenhouse at this time and it was 46 in there last night.

What to do!!!!?

{{gwi:581504}}

{{gwi:581505}}

{{gwi:581506}}

I would say that the clay pots afford some protection from very cold temperatures because they are porous. Both air and water are good insulators and both are part of a terra cotta containers' make up. Plus, there's the factor of the thickness of the sides.

That's my story and I'm sticking to it! ;-)

Mike, could that reaction be to the sun, rather than the temperature?
Did you gradually move these trees outdoors, or put them right into the sun?

I, too, think the thick walls of terra cotta afford good protection.

Josh

Oh Josh!!!!!!!

Josh: I am a product of my own not listening to my own advice dummy!

I just stuck it out in the sun, not full afternoon, but full day light which leads me to believe they were use to much less sunlight in the room and even just being outside is a bit more intense causing the leaves to sulk! Thank God I did not let them sit in the full afternoon sun, or the leaves would of been burnt besides.

Thank you thank you! If it is them reacting to much more sunlight, then they should perk up as soon as they get use to it.

Rhizzo! I never questioned if clay was better , since I myself am aware of the benefits of clay verses plastic....YOu know that about me.

But I still wonder why clay feels much colder than the plants sitting in plastic. They DO react much differently in clay verses plastic when it comes to the cold., and you know me, I always need the science behind why things do what they do.
It does take much longer for the soil to warm up in my clay pots, especially the larger ones and therefore if the sun comes right out form behind the clouds on an otherwise chilly day, the new growth on the trees in clay droop drastically, and I mean drastically wilts, if the clay is cold to the touch. The ones in the plastic do not do this. Therefore, I have always wondered why?

Maybe the clay is a good insulator, not allowing the soil to warm up as fast as plastic , but at the same time, if the air is very cold, it is going to take longer for the mix to warm up quick enough to keep up with transpiration with the hot sun.

Does this pose a risk to plants sitting in hot sun after a very cold night when temps rise drastically while the soil mix still stays very cold? Should one be concerned about this significant wilting until the mix warms up enough in the pot to keep up with the heat of the day?

I am not sure if this is good at times? What do you think?

For those that took the time. Thanks

I will remember your willingness to help

Mike