Hi all,

Let me introduce myself and my citrus plants first. I live in Finland, and I have a few seed grown Citrus plants. Seedlings, because it's not very easy to find grafted Citrus trees or cuttings in these latitudes.

My oldest Citrus plants at the moment are two grapefruit trees, six years old or so. Both plants are still quite small and live in rather roomy terracotta pots. First years they grew happily indoors, but the spider mites are always troubling and thus I have now carried the trees outdoors for summer.

Last winter the plants spent inside in a cool storage room, and there they are now again. There's a south facing window in the room, but the sun doesn't shine all that much here during the winter months, at this time of year we get maybe six hours of daylight and even that's quite dim usually - it's the rain season... it gets a bit lighter in the real winter, in Jan or Feb when the snow comes and the days get longer again. The room is now around 12C (53.6F)

Anyways, the trouble is that in the begining of the summer I carried the pots outside and placed them in a shadow first (hoped to protect the leaves from burning). Later on I moved them to full sun, fed and watered them plentiffully as I assumed would be good. But the leaves turned yellowish right away. I thought that it's nothing, that the color will change back later, but it hasn't - not even when it got cold again in the fall and I moved the plants indoors. So now the sad looking trees are sitting in the cool room, looking as if they're dying. Leaves all yellow or brown and some of them curled or dropped. I haven't watered them much anymore, so the soil is almost completely dry, this is the way the plants have overwintered before. There's a small clementine seedling right next to the grapefruits and looking just fine and all dark green, so I think the temperature can't be the problem, but maybe the sun burned the leaves and now the plants are dormant and thus don't make new growth. So what should I do now, rise the temperature and give artificial light to the plants? Or keep them as they are and hope that they will re-incarnate in the spring?

If needed, I can take pictures later and post here. But maybe someone can help me even without?

Thanks in advance!
-Jari

Hello JarstaP. .
Don't worry about your trees. They will get green again sooner or later. Some pictures would have been helpful.
To answer your question I need some answers from you.
After you moved them to the sunny spot or before that did they had a new flush of growth?
How much feed/water did you apply?
Now do you have burns on the leaves or brown leaf tips?
What is the pattern of the yellowing?
How much time did they spent outside and how big was the temperature difference (gradient) between inside/outside at the moment you moved them outside?

My opinion is to attach some pictures here and leave the trees for now as they are right now to avoid any further stress until somebody can help you.

Here is a complex guide were maybe you can find some answers.


DOWNLOAD GUIDE

Quote from the guide:
40. What causes leaves to become yellow?
There are several causes. The most common cause is nitrogen deficiency (see Q. 21). Additionally,
excessive watering leaches nitrogen fertilizer so that the tree is unable to take up the fertilizer. High lime
content in the soil can cause iron, zinc, and manganese deficiency (see Q. 24, 26). Girdling of the trunk
by rodents as well as Phytophthora root rot (Q. 31, 33). Sunburned leaves appear yellow. Sunburning of
the leaves occurs when the tree is under irrigated, causing the leaves to cup, exposing the more sun
sensitive lower leaf surface. Some grapefruit trees develop a yellow color in the early spring months
(called spring or winter chlorosis), common in young ‘Rio Red’ grapefruit trees. Grapefruit trees with
winter chlorosis will outgrow the problem. Star Ruby grapefruit have a yellow streaks in the leaves. This
is a characteristic of the variety.

JartsaP, welcome to the Citrus Growers Forum, we are grateful that you have joined. Concerning your tree, my question is: Why would you withhold water until the container is almost completely dry? Trees need water even in the fall and winter months. - Millet (1,147-)

Thanks to both of you for quick replies!

Covrig, I'll try to take some pictures today and post here asap.
There was definately new growth when I moved them outside - bright spring sun always promotes the plants to grow. What comes to the temperature difference, I can't remember for sure, but I guess it must have been about 25C (77F) indoors and maybe 20C (68F) outside but the nights are always cooler, difference between day and night temp might be even 10-20C. No frost, though, I have been taking good care that the cold sensitive plants don't get bitten by frost. Summer maximum maybe 30C/86F in the shade. I guess the Citrus plants may not like the Finnish summers... lots of daylight (here ~22 hours in the mid summer, in Lapland 24 hrs) and rain, fluctuating temps etc. The plants stayed outside all the summer until just before the first night frosts in the fall.

I used liquid fertilizer, NPK 7-2-2 and according to the label it contains 6.3% nitrogen (different forms), potassium 1.9, phosphor 2.2, Na 0.023, Fe 0.014, B 0.0022, Mn 0.00053, Cu 0.00026, Zn 0.00012, Mo 0.00012 and vitamins B & C (???). So no magnesium - guess that could be part of the problem? I can't tell exactly how much I have given it. Watering is even more a mystery, since it rained now and then and of course the plants got their fare share.

Millet, I have tried very carefully to avoid overwatering, since I have lost some plants because of it in the past. Cool place, little light in the winter means that most plants don't need much water and the excess water just makes the roots get damaged and also may introduce gnat larvae to the soil.

Did you look for red mites?

Isn't red mite the one that lives in chickens? Anyway, usually the mites attack the plants only indoors, out in the open they never trouble... or do they?

That tree sure look thirsty. The leaves also look speckled, so as Sylvain suggests you should look closely for spider mites. Grapefruit like to grow in warm/hot humid environments, therefore they can be difficult trees to grow in indoors as container plants. - Millet (1,145-)

You said you kept them in shade (not partial shade) before you moved them in the sunny spot and by the look of the wrinkled leaves I think the temperature shock was too big for them.
You need to move them gradually from inside to outside and the other way around especially up there in the Nordic countries. I had some lemon trees that looked just like yours after I haven't moved them gradually outside. I still have one that had a shock in May and now has recovered 70%. It has changed most of his leaves.
From my experience if the day-night temperature difference is more than 10-15Celsius every day they will not adapt to the outside conditions so fast. In the future you need to wait more until you move them outside or do that very slow.
All of my citrus dropped some leaves (10-30%) when I moved them inside. It is a natural process.

In your case it also looks like a lack of water and possible a spider mite infestation. They still need water in winter but not that much.

Until the next flush of growth they will look like that. Since you keep them in the cold they will not have one until it will get warmer. If you have where to keep them in a warmer room don't hesitate to do it.
Don't worry they will recover either way.

Grapefruit is notorious hard to grow in your climate on their own roots .

Try and get some cold hardy varieties for your climate. If I know well Finland is one of the most advanced/rich countries in the world (if not in the top 3) it shouldn't be a problem to find something there suited for your climate there. Meyer, kumquat, calamondin..

Thanks for advice.

I do have some Poncirus trifoliata seedlings too, they're almost too hardy to survive even outside (well, maybe after some more global warming... they should be hardy to -10C or so but on some winters the temp goes below -30C...). But I would very much like to keep these trees alive too, since they're my oldest Citrus plants. Then I have small lemon and clementine plants too. Other Rutaceae plants I have are wampee fruit and murraya - both on a windowsill and doing quite badly. Not citrus, of course, only distant relatives.

There's one older man in North-East Finland, who gets own grapefruits from a seed grown tree which is always inside next to a window and I believe even in an old, drafty log house... there's a respectable achievement!

Even if Finland may be a rich country, I'm not rich and there are no Citrus plants for sale in Finland except over-priced small Calamondins in flower shops. I would happily except calamondin to my collection, but I'm not willing to pay the price since I don't count it as a proper fruit tree but just ornamental. I have planned to order a lemon or something from somewhere like Italy, but the costs are too high for a plant which I would probably kill in a few months anyway. I'm also interested in Poncirus-Citrus hybrids, but the seeds are not easy to find. I actually got some seeds once, but I think they were too old since none germinated.

So, back to the grapefruits: I think I'll now give them some water and either raise the room temperature by a few degrees or carry them to inside the house. I will also make a thorough spider mite check, maybe spray them with pinesoap water or pyretrine? I already tried to find a fertilizer with magnesium in it, but failed so far (at least there's no such thing in supermarket, but maybe I can find it in plant shop). I'm just afraid that inside the house in the winter the air can be way too dry for these plants and then I'm in trouble with the spider mites.That's the usual cause of Citrus and Capsicum deaths here...

Dear JartsaP,
I you type of weather keeping them warm in winter is perfect. 99% of the citrus rules you find on the internet are for warmer climates. If you manage to keep them warm (don't forget about the high light requirements) they will grow faster. Fruit from your trees is next to impossible if you don't graft them. They will probably never flower.

In you type of weather you keep them active only a few months a year so most of the year they are dormant. A 6 year old grapefruit tree should have been high.
If you keep the room's humidity high you will not have any problem with the mites. Use some Miticide/Acaricides to prevent them appearing. You can easily find it in any garden shop. It is very cheap and effective (1.5euros in my country). You can put in a tray some weather next to them or even in the pot's tray if you put some rocks there to prevent the pot touching the water.

Here is a LINK were you can find super hardy specimens. Just translate it with Google translate if you don't understand Deutsche (German). I know citrus which will withstand -25C easily and constant. To -30 nothing will survive.

In Romania the most people earn around 250Euro/MONTH. When I hear someone from a developed country complaining I always get a good laugh. I was in the US for some years and in numerous occasions I have heard complaints from people that were earning over 4000$/month or more.
But I know that with higher paychecks you have bigger costs. But common!!!
Please take this as a joke. Don't get mad on me.
And even with these numbers here in my country you can see very often citrus in pots when you are walking on the street.
I know that in colder climates they are very hard to find at a reasonable price or just find them.

Calamondin are not only ornamental. Not at all!I always use them for tea and I like eating them. I like they fruit a lot and very easy all year round. Kumquat is even more adapted to indoor growing (you won't believe the quantity of fruit). I always end up giving to friends some of them.

For magnesium you can use Epsom salt. It is easy to find and cheap also.

I have sent you a PM with my contact if you wish to talk more and help you with other things.

Some pictures of some of my indoor citrus. They stay inside for the winter and this year I didn't moved them outside. They still flowered and set fruit. The Calamondin was so loaded with fruits that I was afraid it was going to break so now it has only 50% of fruits left after I have ate/clipped a lot of them.
Have a good one!

JartsaP, over watering container trees is not the cause of damage or death of citrus trees. What actually damages, and kills the root system is the lack of oxygen. The cause of this is not the water that was applied, it is the growth medium (potting soil) that the tree is growing in. Growth mediums that have become compacted, or growth mediums that do not have excellent aeration, are growth mediums that have insufficient porosity, thus low root zone oxygen. Mediums that contain high levels of CHC or pine bark, such a 4:! CHC/peat moss, or pine medium blends such as 4 parts pine bark, 1 part peat moss, and 1 part coarse sand, can be watered 10 times a day without any difficulty, because the root zone oxygen level excellent, and the drainage is rapid, therefore the roots always have plenty of oxygen. Additionally, the CO2 given off from the roots can easily escape. When a tree dies from "over watering", the actual problem is the the growth medium, not the amount of water. - Millet (1,153-)

Millet, that must be true.I did already know that the citrus plants like air on their roots. My own mix is, if I remember correctly, partly "rhododendron" soil mix (composted peat, wood pieces etc.), partly sandy pot plant soil and partly either perlite, vermiculite or light gravel. Could be all. And the pots are also of breathing material. I think it should have quite good drainage, but in cool air the soil still retains quite a lot water and if the plant doesn't use it, it stayes there for a long time since there is not much vaporizing.

I am also aware that it's possible that my plants will never flower. I just take the risk. Of course it would be magnificent to have some fruiting plant, but I also like the look of the plants (except just now) and the idea of having them.

About Epsom salt and the mite poison: Never seen either in Finnish shops. I just read from some internet site though, that someone had buyed Epsom salt from some pharmacy - some other one answered that he/she didn't get it even from there. I think I might have some old magnesium pills meant for human consumption, would they do and how much is a good portion? I have to ask from some garden center for the mite poison, but it's possible that if it even exists in Finland, maybe it's only meant for professional use in greenhouses... this kind of chemicals are usually very strictly regulated in here and either not available for private use or not at all. Some can be bought but only in large packages. And only the mildest and least dangerous are freely available for private persons and in small packages.

In the winter and with central heating the indoor air humidity can be even <10% and the spider mites LOVE the conditions.

Now I watered the plants today, moved closer to window and raised the temperature to +15C.

With a 4:1 CHC peat moss, it would not matter if the room is hot or cool. All the water would absorb into the chip, (up to 7 times the weight of the chip) and the oxygen level would be about 50 to 60 percent of the medium, never less. With a CHC medium your tree would NEVER have a problem staying to wet, no matter what the temperature.- Millet (1,144-)

How harmful is it to water citrus with cold water?