Hello there, I hope you can help.

Bought a lemon tree end of summer last year, has been constantly dropping leaves since, was in a south facing bedroom window (radiator turned off), using winter citrus feed 18-18-18 at every feed. In the last month I have been taking it outside for the day and in for nights as its 3-6 degrees at night here. The last few nights its stayed outside when above 5 degrees. Recently changed to summer fertiliser 25-10-18 I think. Recently repotted using Citrus Compost only, but quite worried as it looks to hold in moisture easily.

Some of the leaves are also turning yellow, especially the new growth. Also the tips of the branches were turning brown, so I chopped them back slightly. The tree used to be on one of those circular things, but Im trying to open it out more, hence the ugly appearance.

Is there anything I am doing wrong? Can I put it in my greenhouse constantly, will it be ok over night?

This is the same post as UBC website:

http://www.ubcbotanicalgarden.org/forums/showthread.php?t=24715

Pictures are attached. Thanks.[/img]

I can only assume your 3-6 degrees there is in celcius...at least I hope so! I believe citrus is always dropping older leaves but for the new leaves to turn yellow and drop as well...maybe it is too much fertilizer. You said you use it at every feeding. Leaf tip burn is a good sign of fertilzer issues.

I would stop the fertilizing, keep it in a warm, sunny area with some humidity. Water only when the top 3 inches or so of your container soil is dry. Also check the underside of the leaves and make sure there are no mites. Just my two cents. Hopefully others will chime in and have some better info for you.

Thanks, the photo's are attached to the link above, the new growth does not seem to be dropping, its the green leaves that are dropping, about 5 yesterday. But the new growth is definately very yellow.

The instructions say to fertilise at every feed, but will only give it water for a while.

Could it be that the tree is outside in direct sunshine, but the airtemp is only 16-22 degrees centigrade?

I think Ohiojay may be right about excess fertilizer and the ratio of 1-1-1 is not good for citrus. Citrus use fertilizer in the ratio of 5-1-3 and in container plants it is best to match that ratio as much as possible.

Your second problem is probably the cold root-direct sun scenario that has been mentioned so often on this forum. If you leave your plants outside when the temp is 5 C (41F) the roots will be below 55 F and the roots will be completely non-functional-- even at 60 F they are barely functional. Therefore when the sun comes up it begins to cook the leaves and the roots can't supply moisture for cooling--dead leaves are the result.

Ben:
I saw the picture of your citrus .
I think your plant needs nitrogen and or iron or both.
There are some reason why your plant can not take in those nutrients.
One reason is the soil is so high in salts that your pH value is so high or so low that the plant can not take in those nutrients.
In your case maybe it's time to change the soil with a good draining and with less fertilizer.
You are killing your plant with kindness so much that your soil becomes toxic to your plant with too much fertilizer.
Read the label how much you put and then reduce that in half ( because your plant is in stress right now).
Make sure the fertilizer you use is close to 5-1-3 proportion and this is important: make sure it has micronutrients added.
Another reason is overwatering. One thing you can do is soak the soil and run the water (gradual only) for at least 10 minutes to get rid of the salts in the soil. Then stopp. Wait until the top of your sil is dry to the touch or the pot is lighter than when you started.
You will see in 2 weeks time new growth and new buds.

Blimey, thanks for the speedy reply guys. Right, will change the soil tonight, how about equal amounts of orchid compost / citrus compost / washed grit?

I will also order some xmas lights, but when should I use them, permanently? Will aim to get soil above 70dF.

I used Christmas lights on mine anytime that the nighttime temps were below 60 F. The garland type of small lights raised the temp of my pots about 15-18 degrees. They were unable to keep the soil temp above 60 when temps dropped into the 30's -- on those days I just kept the seedlings out of the sun (in my shop).

The first 2 are great but what is a washed grit?
You can add course sand as big as BBs to enhance drainage and some pine bark and perlite or vermiculite all of these are to enhance drainage but not fine sand- won''t help. And add some long lasting fertilizer such as Osmocote which is good for 3 to 4 months and mxed in with the mix. Then maybe you don't have to fertilize anymore for 4 months. Which is your problem in the first place (I think).
That is a good idea to raise the soil temp over 64*F up to 90 I believe to enhance root activity for growth and new leaves.

Right, will repot now, before it gets too dark, grit is the same as vermiculite i guess, like gravel but smaller, used for horticultural things over here such as weed control.

Will also source some lights, being the wrong side of xmas not sure how lucky I will be, what about reptile mats, I could put one in my greenhouse and stand all my citrus on it? Ever heard of that before?

First of all whether you fertilize every time you water, or whether you fertilize once a week, or once every two weeks really does not matter at all. The important criteria is not how often you fertilize, what is important is the parts per million (PPM) of nitrogen you apply with each feeding. You certainly can fertilize with every feeding and obtain very good results if you apply the approbate PPM that should go with that type of fertilizer program. The Citrus Clonal Protection Program (CCPP) at the University of California (UCR) fertilizes their container citrus at 300 PPM with each and every watering. I fertilize my container trees at 250 PPM. Concerning your lemon tree, one thing that is absolutely certain is that your trees problems are in the container's soil , and is cause by your cultivation methods. In my opinion....1). your tree is not in an acceptable container, the container is to small for the tree. 2). you are growing the tree without knowledge of the containers soil temperature, and what the tree's leaf surface temperature is as the tree is setting all day directly in the sun through a south window. 3). the type of fertilizer formulation you are using is for trees grown outdoor in the ground and not for a container grown tree. 4). the growth medium you are using has very slow/poor drainage, thus the soil oxygen level will be greatly inadequate, and the soil CO2 level will be too high. The minimum oxygen volume in a container's growth medium needs to be 25 percent of the volume of the container, and this level needs to remain the same six months down the road, and the same one year down the road. There are many good types of growth mediums that you can plant your tree into. The most commonly used medium by the industry is 1-part conifer (pine) bark, 1- part COARSE peat moss, and 1-part COARSE sand (Not play sand). Another good medium is 4-parts CHC and 1 part peat moss. Lastly, by looking at the pictures, you probably have never nourished the tree with the trace minerals that are required by citrus. You should have no problem putting your tree outside when the temperature is 16-C (60F) because the sun will quickly heat the containers growth medium to at least 26 - 28C. When the tree is setting all day directly in the sun through the south window be sure the root zone temperature is at least 18C (64F). For now be sure your growth medium has EXCELLENT, EXCELLENT drainage. To accomplish excellent drainage, you must incorporate some coarse chunky material. The three most important ingredient are 1. soil oxygen, 2. soil oxygen, and 3. soil oxygen. - Millet

Grit is not the same as vermiculite. Don't use vermiculite. - Millet

Right, repotted last night using equal measures citrus compost / grit / orchid compost. Also left Christmas lights wrapped round the base last night, soil temp was 85 F this morning, so I put the trees outside on my deck, they will receive good light but only 2 hours of direct, I didnt want to stress.

Millet - the current root ball is about 2cm smaller than the inside of the pot, I have been warned about placing the tree in a bigger pot due to root rot, how big do you think I should go?

Thanks again guys, I dont want to be a citrus murdered!!

2 centimeters is only 3/4 of an inch. If the tree was in better health and was a large tree I would follow the 4 inch (10 cm) rule. In your tree's case I would transplant it into a container 2 inches larger (5 cm). Don't let the trees soil get to warm. 70F is plenty during the winter months. If you don't have a soil thermometer yet, you might consider purchasing one. Now that you have replaced the growth medium, be sure that when you irrigate the tree the water drains through rather quickly. Good luck to you and to your tree. - Millet

Thanks, I also drilled many more holes in the bottom of the pot, to aid the drainage. I have ordered a heat mat 120cm x 40cm, thats large enough to put on a shelf in my greenhouse and keep the roots 70F ish for all of my 7 citrus trees.

Then I will keep them outside when it gets a bit warmer, is that a good idea, so long as the roots are active?

Have also ordered a digital meat thermometer.

Thanks for your help.