Greetings, esteemed botanists ans citrus specialists, please share your wisdom and help me keep this little citrus alive. I bought it some weeks ago from an exotic plants shop, I watered it carefully so it wont get overwatered. I placed it at the window for maximum light (not so much since it's winter here). The house temperature is around 20-25 degrees Celsius (77 Fahrenheit). Sadly, last week I noticed some leaves drying and falling. Looking at them closely found that they have some black areas, searched the internet but couldn't find much, so thats why I came here to you, for advice. I am posting photos, hope they are good enough.
First photo looks like possibly botrytis. I would suggest removing the leaf (or leaves). Botrytis is not too serious as long as you do not have cool damp conditions, which would be unusual in a house. Second photo looks like minor physical damage or possibly sooty mold fungus, does it come off if you rub it? Sooty mold is not too serious either, but is sometimes an indication there are other pests such as scale which secrete honeydew. Look closely as they can be hard to spot. The third photo looks like a very happy citrus. Keep in mind that when you buy a citrus the conditions it was growing under change and often result in leaf drop, particularly when it moves into a darker and dryer environment such as going from a grower's greenhouse to a residential house.
Thank you so much ! Can you please tell me when it's the best time to move it in a larger pot, now or in the spring ? I bought citrus soil special for it, fertilizer and a very nice ceramic pot, but don't want to do any timing mistakes.
Your problem is very easy to understand. Light is the most important variable affecting the productivity of citrus and indoors sometimes unless you add grow lights is not enough. Transpiration is the process by which moisture is carried through plants from roots to small pores on the underside of leaves, where it changes to vapour and is released to the atmosphere. The transpiration rate is a function of ambient temperature, root temperature, leaf temperature, humidity and light. As a reference point, a greenhouse overwintering citrus would have a temperature of say 77F and RH between 60-70. Your home is 77F and your RH is probably between 30-40. When you have a high temperature and low humidity it creates a high transpiration rate where the plant is exhausting moisture too fast. This is why leaves are drying out, dropping, and browning. What you can do is lower your temperature, increase your humidity, use a humidity tray at the base of the citrus, and use a very small fan. Air flow will help the plant leaves cool and conserve moisture. Too much air will do the opposite. A radiant heater in the background is deadly for citrus. You can't grow citrus near any source of heat or cooling. In nature, there is a symbiotic relationship between ground temperature and air temperature which regulates root temperature, leaf temperature, transpiration, and photosynthesis, and metabolism in harmony. When you bring citrus indoors this relationship is very difficult to maintain. Leaves are often shed when there is a major temperature difference between the roots and leaves. Citrus roots don't grow well indoors so repotting is unnecessary and a very bad idea. Citrus prefer to be root bound and I would only repot if necessary in the summer. Google VPD calculator. Other issues are the leaf temperature from the sun, the root temperature, and the amount or lack thereof of photosynthesis. The transpiration rate is a function of three in-house variables: temperature, humidity and light. Also indoors in dry conditions spider mites will suck the moisture from the plant compounding the other problems.
Thank you for the extremely precise instructions. The way I see it, I need to make that humidity tray asap. Problem is, I already transplanted it and now it has quite a sturdy pot, gonna be a challenge to find a tray for it lol. Damn winter :(
Sadly the leaves continue to dry/go brown /fall, even with a humidity tray. Anyone has any idea what should I do ? At this moment, I placed the citrus in the living room, where I have around 77F temp, however the humidity most probably isn't good enough. I can theoretically place it in another room where the temperature is 40-50F and possible a bit higher humidity too. Do you guys think I should move it or just keep it there 1 more month and hopefully he will make it through the winter ? Thanks in advance. These are the current photos.
Hi TheoGrecu, What is your room RH % Outdoor temperature? Hours of the sun in the window? How many months/year can the plant go outside? Take a magnifying glass and look for spider mites on the plant. Look for strands of web and white dots underside of the leaves. It appears you might have them. Spider mites are attracted to dry air. Some quick tips for growing citrus indoors 1) Leaves will drop if RH falls below 50% 2) The roots have to be heated 3) You need air circulation because photosynthesis requires carbon dioxide. 4) Sunlight in a window will bake leaves (95+F). Fan leaves to keep them at room temperature 5) Between 54-72 F very little root activity. 6) Winter leaf drop WLD is triggered by low humidity, cold roots& hot leaves or hot leaves & cold roots 7) VPD vapor pressure deficit is key 8) Citrus in containers like to be root bound 9) Larger pots make it impossible to water properly 10) Clay pots lower root temperature indoors 11) Metal pots are easy to heat indoors. 12) Never put anything in the bottom of the pot, it creates a perched water table. 13) Top reasons for indoor citrus failure, RH below 60%, Sunlight baking leaves, cold roots, not enough sunlight. 14) If RH is below 45 start reducing grow light time 14) If RH is below 40 turn off the grow lights and move away from the window. 15) If low RH is taking its toll put plants in a bathroom where humidity is higher. Here are some idea pictures Growing Citrus Indoors - a Gallery by Lemon Lime Orange Zone 6a
Have attached a Vapor Pressure Deficit calculator. I think when you put your variables in you will be in the red zone, over transpiration. If you are using a fan the leaf temperature and room air temperature will be similar. If you are not using a fan and the sunlight in the window will significantly raise the leaf temperature. This calculator allows you to enter the leaf temperature. You can buy an infrared thermometer on Amazon for $25. In Toronto, Canada with room temperature 22.5C in January my leaf temperature would be 35C exposed to sunlight through the window without a fan. The key is maintaining the correct VPD for your room temperature. Some people can't do it without a grow tent or greenhouse. VPD Calculator by Everest Fernandez
You could move the tree to this room to over-winter provided it is kept in darkness; the tree will be dormant in those temperatures.
I don't know what is my room RH, since I dont have a humdity measure device. I'll look for one but since I am in Eastern EU, it might arrive too late. The outdoor temperature now is under zero (Eastern EU) The hours of the sun in the window are very few, in this time of year. There is some light, but it's winter diffuse light and not direct rays of sun like would you have in spring/summer/autumn. The plant could be placed outside around 8-9 months per year. I looked for spider mites, but there aren't any. No strands of web, no white dots, appart some dried insecticide drops that was sprayed some time ago.
If your skin feels dry the RH is very low. When citrus leaves start losing moisture they start feeling leathery and stiff. I suspect your indoor humidity is very low because of the outdoor temperature. If you can drop your indoor temperature that raises the RH higher. Your other alternative is as Junglekeeper has suggested. Citrus is grown in tropical, subtropical and Mediterranean climates and like high humidity.
I moved it in our bathroom, near the window, the humidity should be quite bigger there. Hopefully it's going to work.
I think that is a good move. Citrus won't bend to our will. They will only grow when they get exactly what they want.
After 4 days in bathroom, near window, the citrus seems somehow stable, however the leaves continued to fall. I noticed a pattern in this process. It all begins with the tip of the leaf drying and going dark brown, then in the following days the leaf goes a bit yellowish, then finally falls. Weird thing is that if I cut the dark brown tip with a scissor, ~70% of times the leaf lives, the citrus has many of such leaves saved this way. My question is this: could this is be a leaf disease or something non related to the temperature /humidity itself ?
Certainly there could be a fungus or bacterial problem, but its severity is usually related to the conditions. For example in my cool greenhouse, where it is cold and damp in winter, I have to be very vigilant about botrytis. Whenever I see a sign of it I nip it off, and use a light oil spray at least once a year when the conditions are starting. This helps to help protect the plants. The two steps keeps things under control. However, once the weather warms up and the RH lowers the potential problem disappears. Keep in mind I have not seen this kind of problem in a house and would not expect a fungus or bacterial problem. I have grown lots of citrus in my home and the only real problems I have seen are pests. Spider mites when conditions are right and they have been introduced in the home somehow. Scale, aphids, and mealy bugs can also happen. These pests can be seen when looking very closely though. However, I have seen plenty of winter leaf drop and the citrus have always recovered nicely from that. I really suspect that the leaf drop you are seeing is normal winter leaf drop. Fungus may get a foothold in the stressed leaves, and cutting any infections may help save a particular leaf, but as long as you provide good conditions the citrus should reach a new balance and probably start healthy new growth within a couple of months. I have started some pages on growing citrus. These pages are particular to my area (southern Vancouver Island), but you may find some useful tips there. I will be adding material as I think of it. Here is the link: Growing Citrus on Vancouver Island | Aprici
Hi TheoGrecu, your citrus looked extremely healthy when you bought it. There are a number of causes of brown leaf tip but in your situation, the most common cause of brown leaf tips or brown edges on leaves is caused by the plant not getting enough water to the leaves. Think about a taco in the oven. When you overcook a taco the tips of the taco are usually the first edge to burn. Your citrus was grown in a greenhouse with (VERY) high humidity and the plant is reacting to heat and humidity stress (leaf drop, brown tips, yellowing) all classic signs of WLD. Dropping leaves is a survival mechanism. The plant will ONLY keep those leaves it can support with the available photosynthesis and transpiration rate. You have increased the humidity and the problem has slowed down but the plant is still not getting what it needs and still dropping. This is very typical of winter leaf drop. The yellowing in winter is usually caused by reduced nitrogen uptake by the roots from the soil in low temperatures. Citrus tree nitrogen uptake is generally lowest during dormancy. The yellowing is a clue that something is dormant. Because you moved the plant to a heavy pot which is most likely keeping the roots cold. Beautiful pot but next time keep the citrus in the original pot and just place inside the decorative pot. I use hot galvanized pails and wrapped with a germination heating pad. Let me give you an analogy: Let's say a city decides to buy solar powered fire trucks because the accountant tells them they can save money on fuel. In the morning the, accountant is all excited because the fire truck is pumping water and the fire is going down and everything looks great on paper. But later in the day the sun is less intense and the solar-powered pumps are slowing down and the fire is spreading and eventually the building burns down. Your leaf is like an overheated solar panel that is not being cooled properly and cannot support enough energy for the transpiration of moisture to the leaf. The leaf will eventually heat up and consume itself. What can you do: Lower temperature, raise root temperature, raise humidity, provide grow light, move plant further from the window, move air around with a small fan, mist the plant, humidity trays, change pots, try a smaller pot, or try putting it in a room with less light and cold to go into dormancy. Air movement is very important. The leaves need constant fresh air for the process of photosynthesis. In a window what typically happens indoors is the stomata close to conserve moisture. This then stops the natural cooling mechanism of the leaves. The sun on the leaf continues to raise the temperature of the leaf until the leaf burns. What you have is what gardeners call cold feet/hot head which is cold roots and hot leaves.
Thank you, the way I see it, the only thing I can do is move it away from the window, even if the window itself doesn't provide direct rays of sun, but only diffuse light. The humidity in the bath is quite big and I am misting the plant too 1-2 times a day, hopefully it will make it to spring.
