Hi all, we have had cold weather here the past week. Last night we had -4C (25F) where I am, including inside my greenhouse. The heating thermostat failed to kick in it seems, son of a.... When I opened my greenhouse this morning I got a very strong smell of citrus leaves. I've never had this happen before. No leaf drop yet, the leaves are drooping though. Is the strong citrus leaf smell a sign that the leaves have frost damage? Is this a bad sign?

I checked the greenhouse this morning. The strong citrus leaf smell is persisting. Leaves are drooping. Small tender growth is shrivelled and browning. No leaf drop though.

The soil in the pots seems to be slightly frozen. I can't warm the greenhouse yet because I have to buy a new heater, the old one has chosen the worst time to brake completely.

Should I water the soil to help unthaw it or would that make things worse?

Any help or advice appreciated, thanks.

The best what you can do now (if not already done) is to protect them from the sun. Use a curtain (inside) over sun facing walls of greenhouse.

Warm the roots up quickly!! Fairly lights, heat mat, anything

And give warm water (I didn't say hot).

Thank you very much Ivica, Beno, and Sylvain for your replies and advice. I have done what you each suggested. There is still no leaf drop, just drooping and browning of small tender growth. Hopefully there will be no lasting damage to my trees and seedlings.

Lemandarangequatelo,

good luck with your plants! Yeah, my brown select looks the same way... No leave drop, lot of curling and browning of tender growth.

Regarding the heater, perhaps, you can have a simple cheap and not too powerful heat blower that you would turn on/off manually in case of freeze and an automatic one that would kick-in if needed? Electronics have a sad tendency to fail.

Hi GT, thanks for your reply and advice! I hope your Browns Select Satsuma is ok and has no lasting damage. Does it also give off a strong citrus smell that you didn't notice before?

Your heater idea is great, I had the same thought so I did exactly as you described. I now have a 2KW convection heater on a thermostat as my main heater, and 2x 180W tubular heaters as backup for the coldest nights (tomorrow is projected for -5C/23F).

I still don't trust the electronics though as you rightly pointed out. I'm thinking of having some sunflower oil floating candles as a second backup.

Lemandarangequatelo - Yes, this cold weather is getting annoying. Last night my greenhouse frost alarm went off at 4am. Wife not pleased. The fuse had blown - probably not surprising as its a 3Kw heater that's been running nearly continuously for about a week.
I would recommend using a fan heater, rather than a convector where the hot air rises straight to the greenhouse roof. A fan blows the air more along the ground and circulates it amongst the plants. It also helps a bit to prevent fungus diseases.
Most of my greenhouse is also 'double glazed' using bubble-wrap. This definitely reduces heating costs a lot, especially as I've fixed it right across the greenhouse roof so as to cut off most of the apex. So the total volume requiring heating is reduced.

Hi Citrange, thanks for your reply and great advice! I share your pain, 4am, ouch! We stick these electrical systems in for just this kind of weather and then they fail when we need them, lol typical. I hope you don't have any further trouble this winter. I will definately implement all of your suggestions.

I would be concerned because of the frozen soil in a container citrus. If it killed off lots of the roots (certainly many small ones near the container edges and top are likely dead) you may not see signs of leaf drop (just droop) until the foliage needs significant water. For example, heating up your greenhouse to a point where humidity is low, or the leaves are very warm, or allowing a lot of direct sunlight to hit the leaves, or when Spring comes and the tree is no longer in acquiescence. At that point, it will unavoidably experience leaf drop, since the damage was already done. It will drop as many leaves it has to, eventually to be come into balance again with the remaining functional roots.

I learned my lesson last year that in container citrus, the root zone is the first thing to protect in frost weather. Oranges and mandarin foliage can handle 30's and (hours of) upper 20s weather, but the limes and lemons will need leaf protection.

But like others have said, you can have hope and keep things in line from here out.

Hi C4F, thanks very much for your informative reply! I was wondering what was going to happen next and you answered that for me. I won't be too worried then if there is leaf drop, but I will be worried if new growth doesn't appear in spring! I hope all your citrus are doing great this year.

GT, thanks for the good wishes. I hope your Browns Select will sprout anew in spring. Good luck to us both!

Just to offer further hope, if the soil wasn't frozen for a long period of time, don't toss out your tree even if you don't get any new growth in Spring.

If the tree hasn't experienced "die-back" where most of the leaf-less twigs brown then die, it's possible the tree may stay in "stasis" with just a few leaves, all drooping, until it can *very* slowly build back roots. Be sure to cut way back on the Nitrogen part of your fert, but keep giving it the PK and micros (I bought a small bag of CRF that had a 1-1-1 ratio and used my normal micro supplement which was 0-0-1). Otherwise excessive N could end up forcing the tree to attempt foliage growth before it's ready.

I tossed a few of my container orange trees which had lost almost all leaves from the freeze experience; it's possible they may have come back to life eventually. It's not uncommon for those in lower zones to lose most if not all the top of in-ground Citrus due to freeze, but if the roots are still sufficient it can make a full recovery. The roots are the key.

In short, I'm saying don't lose hope as citrus can be a lot harder to outright kill than other trees.

Good luck

Thanks C4F for the further info and advice. That was very reassuring, I won't give up hope. I can't find a 1-1-1 fert but I found a 5-5-5 fert, would this be suitable do you think?

Update on my trees. No leaf drop yet, but leaves are still drooping and turning brownish. I have found on one of my trees a few of the very top leaves are dry and crunchy. The trees don't need watering so I assume this means some root damage is stopping water getting to the top of that tree, hopefully the root damage isn't extensive.