THE AGRONOMIST ANSWERS ON HOW TO GROW AND CARE FOR PLANTS
MY LEMON PLANT IS IN BAD CONDITION DUE TO THE COLD
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QUESTION BY ALESSANDRO
I came across your site and found it splendidly interesting. I am a plant enthusiast, with a particular fondness for green and fruit plants.
I turn to you about a big problem I have with a beautiful (until recently) lemon plant that I have had in a pot for 19 years. I state that I am very fond of you and I take care of him like a son. This winter, however, due to my home move, I was also forced to move my beloved plant, which unfortunately, due to the sudden frosts of this winter and my absence for several days, is now quite bad.
In previous years, in winter, the plant was placed in a very sheltered position, albeit outdoors and with quite harsh climatic conditions (I live in Verona). This year the temperature dropped incredibly down to -6 degrees and although it was as sheltered as ever, the rigid temperature unfortunately reduced my plant in very critical conditions; on several branches it has lost its leaves, the fruits that were in the growth phase, have presented huge brown spots tending to black, then slowly becoming soft until they fall, and the branches in question now seem to be drying up, as from green they are slowly turning brown.
Only a part of the plant is reduced in these conditions, another side seems to have more or less resisted, perhaps the part less exposed and more sheltered by the wall near which it was.
Now the plant is in its new home, it is on a very large balcony on the second floor of a building, in a position of full sun from morning until late afternoon, sheltered on one side by the wall of the building for its entire height ( the plant is about two meters high), and on the other always from a low wall for about half of its height. I see that the leaves before falling, even if they are very green, become soft, very weak, and then fall precisely. The branches are slowly drying up, as already mentioned, and only two fruits present on the branches apparently still quite green, remain hanging.
At this point, kind agronomist, I appeal to your wisdom to know what I have to do in an attempt to save the plant, at least try with that part that at the moment seems to be still alive and with beautiful green leaves.
The situation is very serious and urgent, I would like to intervene in the best way, as quickly as possible, I suffer from seeing the plant in this state, and I would not want to commit wrong actions that could further compromise the condition.
I therefore remain anxiously awaiting your kind reply.
Thank you very much.
Alessandro (March 6)
I thank you very much for "His wisdom" but that is not the case. I only try to help you, as far as I can, nothing more.
From what you tell me the situation is not pleasant. This year, both for the heavy rains and for the cold weather, was a real disaster. You tell me nothing if the plant was exposed to rain or not or if the pot was somehow repaired.
You tell me that the leaves do not change color or show discolored areas but become soft and still fall green. This makes me optimistic but to be safe, do a check of this type: skin a "healthy" area of a suffering branch near the dry part and check the color of the underlying tissues: if they have a yellow-orange color up to reddish (such as photo below) compared to the light color they should have.
It's a scruple, but better check. Let me explain: the doubt is that he may have contracted the dry sore (a fungal disease which is the most serious that the lemon can contract which is caused by a fungus, the Deuterophoma tracheiphila Petri).
Frosts or too low temperatures are a real cleaver for the plant and you have to be very careful because the symptoms do not appear immediately but sometimes after weeks.
What happens to the plant. Let's say that the reactions are different depending on the organs affected. On plant tissues, the effect of frost is usually similar to dehydration of the cells (there are also different cases). The dehydration of the cells is the first consequence of the reaction of the plant when the temperature drops beyond certain limits: to concentrate the cellular juices and therefore lower the freezing point, it eliminates the water from the cells. In the presence of low temperatures in the intercellular spaces, the water lost by the cells forms ice crystals. If the dehydration of the cells is not excessive and if the temperatures return to normal values, the cells slowly reabsorb the lost water and resume their activity, without damage; but if this does not happen, as the temperature increases, the dehydrated tissues wither and take on an aspect that agronomically is called "allessatura" (the one you observe on the leaves) and moreover the presence of water in the intercellular interstices causes the air to escape causing the asphyxiation of cells resulting in their death.
Since you don't tell me about it, I assume you haven't observed any damage to the woody tissues ie splits, noticeable lesions or detachments of the bark. This is a positive thing and this should not surprise you beyond the drying, because it means that the woody organs have not been damaged by the cold.
Now the biggest problem you face at my start is certainly at the level of the root system. From what you write I think that he has not taken steps to protect the roots in some way by arranging the ground, for example, mulch in order to reduce the heat loss of the soil (and therefore maintain a higher temperature at the root level) and since he temperatures dropped a lot and for long periods, the root system could have been damaged. This would be no small damage as you can easily imagine because it means that the "heart" of the plant may have been compromised.
In consideration of all this and starting from the assumption that we are not dealing with dry sore, first of all I advise you to immediately remove the two surviving lemons (it is useless to make the plant waste energy in completing the ripening of the fruits when you must concentrate in its survival) and then to flare the lemon to check the health of the roots. Take some shears (clean them well and disinfect them over the flame before using them and try to work as "cleanly" as possible) and remove the roots that you will eventually find rotten (you will feel soft to the touch) or dead by cutting at least an inch above the part damaged. Get a broad spectrum fungicide powder that you will need to dust on cut wounds.
Then repot and wait at least 7-10 days before watering in order to give the wounds time to heal (protect the plant from rain too). Then resume normal crop care and administer a fertilizer (in small quantities as you have to take into account the decrease in the crown and possibly the root system) that is not particularly rich in nitrogen (excessive nitrogen fertilization makes the plant more sensitive to frosts) but that has zinc, copper and boron which are microelements necessary for growing tissues as well as phosphorus and potassium which make the plant more resistant to cold as they favor the concentration of cellular juices. , to be careful, get some inert material such as straw or wood shavings that you will place on the ground for about 10 cm thick (press it a little) in order to protect the ground from any temperature changes and therefore from a loss of heat.
In the aerial part I would advise you not to touch anything for the moment because pruning stimulates the vegetative activity of the plant and at this moment it is not really the case to stimulate anything. Only when the weather has finally stabilized on milder temperatures will you cut the dead branches.
For the future, if you see temperatures drop too low, place a clear plastic sheet over the plant which is the best protection against the cold for potted plants.
If the root system has not suffered excessive damage and the plant is strong it will recover. Let's be optimistic.
Keep me informed.
Dr. M.G. Davoli
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