Hello everyone, this is my first time here, and I could really use some advice! See attached pictures and at least read the last 2 paragraphs for shortest version! We have a dwarf variegated pink lemon tree, that was given to my husband about 12 years ago by a close family member who passed away about 6 years ago, so this tree is very special to us. Being in Ohio, every year we put it outside during the summer, and then acclimate it to be back inside over the winter, and we have never had any problems with this tree, until now. In the late spring last year we did re pot it because it needed a larger pot, but that has been the only change over the years: every winter it goes in the same room, on the same table next to the same window. All the sudden about 2 weeks ago the leaves started shriveling up, turning brown and dying. It looks as if the tree is just dying! We can't see any evidence of any pests or mold type issues, although we haven't completely ruled that out. Its also in a room with a fish tank which seems to provide good humidity, again, the same exact environment it has always wintered in for the past dozen years. The branches are dying, its just dying and I don't know what to do! My instinct is to prune back the dead stuff, but I always worry about wrongly pruning it. The absolute only change to its indoor environment is the addition of an African Violet to the plant table, and my orchid just finally re-bloomed, which makes me worry about some type of infestation. Anyway, sorry that was so long! What steps should I take? I feel like I should check the roots are healthy, prune back the dead bits, and possibly add a bit of epsom salt to the water next time? We have never checked pH, we've always had very successful gardens every year and I have never had a problem with a plant that stumped me, but since its been alive and healthy for 12 years, and all this year up until 2 weeks ago when the tree took this quite sudden turn for the worst, I wouldn't think pH would be the problem, and, if it were, I would think we would have seen more subtle signs of distress than this sudden dying. Any suggestions will be *greatly* appreciated!
Welcome to the forum. A few questions: Prior to repotting, had the tree been growing in the original medium it came with since purchase? Does the current medium differ from the original and if so, in what way? Did the leaves wilt at the start of the decline? That is a sign of both under- and over-watering and is indicative of root rot in the latter case. Could this be the result of a thrip infestation? The leaves of the African violet don't quite look healthy. Thrips Management Guidelines--UC IPM
In nature, there is a symbiotic relationship between ground temperature and air temperature which regulates root temperature, leaf temperature, transpiration, and photosynthesis, and fertilizer in harmony. When you bring citrus indoors this relationship is very difficult to maintain. What is your room air temperature, humidity, soil temperature? How many hours of sun does the plant get? When did you last fertilize it and with what? The short answer is the humidity in the room was too low and the leaves lost moisture too fast and it was accelerated by high room air temperature, low root temperature, and ultra high leaf temperature, and poor transpiration due to the size and shape of the pot and possibly a change in media. Citrus likes to be rootbound. When you put them in a square pot they probably didn't like that. A round pot is much better because it waters evenly. A square pot is going to be different moistures on the corners vs the sides. The pot also looks a little bit big. In physics, there is a principal where water does not pass from one substrate to another easily. Never put stones in the bottom of the container or change from one media like pine fines to peat moss because they are different substrates and the water would wick away from the roots. Citrus prefer 60-100% RH. That is very hard to achieve indoors. To raise the humidity you can lower the temperature and use a humidifier and a humidity tray. You have to keep the humidity of at least 50%. Google VPD calculator and put in your RH and temperature. You want to keep the VPD as low as possible. When VPD is high your plant is going to lose moisture faster. Remember you have no wind inside to cool the leaves. Sunlight in January in Ohio can heat a leaf up to 100F. A small USB fan can drop the temperature by 20-30F. Root temperature is another big issue. Between 54F and 72F there is not much root activity. Root activity increases in a linear fashion from 72F to 85F. The temperature of the root ball is usually a little lower than room temperature because moisture is evaporating and will cool the pot. In my situation, I grow indoors with LED lights and I use hot galvanized pails surrounded by a germination pad controlled by a thermostat. I keep my roots at 85F. When you water use 85F-95F water to raise the temperature of the roots. If you are using cold tap water that will shock the plant every time. I don't know how much light you have. Some people can continue growing indoors in the winter and others just try to keep the plant dormant. If the tree's metabolism is too fast during winter because the temperature is too high and does not have sufficient light, it metabolizes more substances than it can generate through photosynthesis and consumes itself. If you have limited light you may want to bring the plant further away from the window to keep metabolism lower.
