Hello, new to the board and need some feedback. I recently purchased a Persian Lime tree, and it doesn't seem to be doing so well. Live in Raleigh, North Carolina, and I recently brought it in to beat our first frost. It was doing really well when outside this Fall but bringing it in seems to have upset it. It's in our back sunroom so it's getting partial light, it has slow-release fertilizer, and I water when finger at 3" depth appears dry. Also thought I'd mention that it was flowering had small limes on it when I purchased it. The seller mentioned it typically flowers in the Spring(?) so I thought maybe it's cycle/season is out of whack and causing it to be unhappy. Should I keep outside to allow more sun and only bring in when it gets down to 40's? And/or can I cover it at night? New to the plant caretaking game so any help would be appreciated. Thanks!
The tree probably has cold roots (<55 F) while being exposed to sun. You have 2 options,-- take it out of the sun and keep the roots cool, or leave it in the sun and warm the roots. For more info, you can search for and read several post by Millet regarding root temperature and exposure to sunlight. There are several ways to warm the roots. Skeet
Thanks for the reply, skeeterbug. But, I'm a little confused. The tree is inside now so I would assume it has warm roots(?), while receiving partial sun due to its being in back sunroom. Thanks again.
The roots need to be above 55 F preferably above 60 to be actively absorbing moisture. Is your sunroom heated? What is the nighttime temp on the floor where the roots are? If the early morning sun hits the leaves before the sunroom warms up the leaves will get cooked without moisture from the roots for cooling. Get a chef's thermometer that will read temps in the 40 to 100 F range and stick it in the soil to check the temp--especially in the early AM. In the ground outdoors, tree roots are much warmer than air temps, especially deeper in the soil, therefore, the trees do not suffer from winter leaf drop when exposed to sun and can withstand temps near freezing without problems. Skeet
Thanks again, Skeet! My apologies for taking so long to respond, but I've checked soil temp using a meat thermometer. The early morning temp seems to hover around 60 (+/- 3 degrees). Although I still have several leaves remaining, I continue to loose leaves. As an experiment I've moved the tree further from the windows, into a shadier portion of the room. The sunroom is extension of family room (about 20x40), and it is indoors and heated (thermostat set at 68). I have the tree in the original pot in which I purchased it. That pot is placed in another pot that sits up off the floor so the tree doesn't sit directly on our (wood) floors. I'm still a little concerned, and still a little clueless as to what to do that'll be best for my tree. I'm considering Xmas tree lights, but I'm hesitant to leave those on while away (and, to be quite honest, a little surprised/cynical that this works...is this true?). I've looked into heating mats, but I don't see this as very feasible either. I was thinking...are there other methods to warm the soil? Maybe a rod of some sort that I can stick into the soil(?) Thanks again, Mike
If cold roots was the problem, moving the plant out of the sun should be sufficient. For warming the soil most of the people use either a string of christmas tree lights wrapped around the pot or they sit the pot on a waterproof heating mat. The other common problem in winter is overwatering since the tree actually uses less water. You mention that you do not water until it is dry at least 3 in deep which is good. What kind of potting material are you using? When was it last repotted? Most materials break down over time and turn to muck which holds water and promotes root rot. If it has not been repotted recently, you can probably lay it on the side and gently slide the tree out of the pot to get a look at the roots. They should be a healthy white and firm-- not brown and mushy. Skeet
For what its worth, I over winter my potted citrus in my unheated garage which is attached to the house and it doesnt freeze (with a S facing window)(I live in a USDA Zone 8). Its cool with temperatures usually less than 10c (50f).You could set up grow lights if no natural light is available. The citrus remains dormant, I dont have any leaf drop problems at all, & the fruit remains on the trees. I havent had to water since i brought them inside around November 5th. I think what really bothers citrus is the home heating systems and lack of humidity. Citrus can handle this environment without any problems. Once our days get longer and there is no danger of frost, i will take them outside. Just on the sunny days at first. This is unconventional citrus care,however, It keeps my plants healthy and green through the winter without the hastle of leaf drop, scale and unwanted pests. The Bearss lime is next on my list to get! Greg
I think Skeet is correct. 60F (+ or - 3 degrees) is huge, especially when - 3 degrees becomes 57F. 55.4 F is absolute zero for citrus roots, and also for citrus foliage. When a tree is setting indoors in a sun room directly in the rays of the sun, the surface of a citrus leaf can reach temperatures in excess of 100 F. At these temperatures the foliage requires water from the root system for transpiration in order to cool. However, at 55.4F or at temperatures near 55.4F the roots cannot respond, or respond poorly. Therefore, the only way the tree can get back in balance is to drop it's leaves. When a citrus tree is experiencing WLD (Winter Leaf Drop) the temperature of the root system needs to be raised to 70F, due to the fact that the leaves have already began to form abscission layers between the leaf blade and the petiole (stem). After leaf drop has stopped the root temperature can be lowered to 64F. In Gregn case, his garage tree is in balance. Cool root temperature, AND low light levels on the foliage. Lastly, TTMrBang Christmas lights (NOT X-Mas lights) work very well to elevate the root zone temperature, however, you must use the large size bulbs. - Millet
Hi Millet, I haven't tried the small Christmas tree lights, but on one of the post I read someone tried the small lights and said it raised the soil temp over 70 F. I think I will try it and get back.-- I have seen soil temps get over 100 recently (near the center) increasing from around 50 in just 2 to 3 hrs when exposed to sun while outside temp was in the 60's. I'm sure a leaf could heat just as much if there was no cooling from wind or water. Skeet
Hi Skeet, I don't think the small Christmas lights put out much, if any heat. In a recent test with black containers (results posted on another form) the temperature in the root zone reached 120-F (48 C) in 1/2 hour while setting in the sun ON A PARTLY CLOUDY DAY. I think you read that post. These type of temperatures can damage or kill citrus roots. Merry Christmas Skeet. - Millet
Hi Millet, I do remember your earlier test comparing black and white containers, I don't remember if you provided an ambient temperature and I was assuming summer conditions (could be wrong), but a 40 degree differential is probably in line with what you found. I did do a test with small lights last night-- soil temp was a little above 60 at the start around 8 pm-- it was 78 around 10 pm in the pot with lights ( 1 gallon pot). Ambient pot temp this morning was 57 while the pot with lights was 75-- temp of a pot adjacent to the lights was about 60. Measurement were take about midway between the side and center. Skeet
Great that you made the test to show that the small lights work. The small lights would be a lot easier to work with. When I think of the small Christmas Lights I mean the real little ones, 1/4 inch size. Are these the lights you tested with? When I did my testing with the white and black containers the outside temperature on that day was 60F. - Millet
Yes the small lights I am talking about are the ones that are about 1/4 in x 1 in long--I should mention the string I used was the garland type with 3-4 lights per inch not the single strand type with one light ever 4-6 inches. I think a lot of the heat actually comes from the wire since they use such small diameter wire. Skeet
