Hi, I have 3 potted citrus outdoor all year on the balcony (Meyer, calamondin, and yuzu) and they usually do fine. This spring, though, I started seeing huge, irregular-shaped yellow splotches on the leaves. In April, the garden centre advised repotting with soil for citrus and feeding it with their citrus fertilizer (NPK 3-0-4), which I did at half strength every 2 weeks. I checked the roots at the same time I repotted and they looked okay. The yellow splotches continued, so I switched to different citrus fertilizer, NPK 2-2-5, because I thought maybe there was a phosphorous deficiency from the former fertilizer. No significant difference in the splotches. Back to the garden centre in July with samples, they diagnosed chlorosis and gave me a chelated iron (+ manganese and zinc) treatment, which I did in July. It seemed to make the problem worse because within 2 days of the iron treatment, leaves got dramatically worse before getting slightly greener for a time. I did a second iron treatment in September and the problem now is worse than ever. The chlorosis diagnosis was obviously wrong (I gave it to my other citrus in September too and now they are all in the same sad shape). I am at a complete loss and rather fearful of trying another treatment that does more harm than good. Other info: fruiting is normal, lemons developing without issue, new growth is slow. I had spider mites in late June but treated the trees successfully, all products I've bought and used have been specifically for citrus and organic (except I guess the iron treatment). Thanks for any insight you may have!
I think you've identified the problem as being a lack of nutrients. My first thought when I looked at your photos was that your plants are lacking nitrogen. But, what do I know, never having grown them.
Have a look at this document: A Guide to Citrus Nutritional Deficiency and Toxicity Identification. Citrus nutritional deficiencies can usually be avoided by using an appropriate fertilizer. I suggest you switch to a high nitrogen, water-soluble fertilizer containing micronutrients. For example Miracle-Gro 24-8-16, which is readily available in our area.
Hi Margot, hi Junglekeeper, thanks for your responses, I appreciate that and I am checking out the link. I guess I should have said that all of the fertilizers I applied are water-soluble and have micronutrients already. When I look at the information on the link Junglekeeper sent, it looks maybe like magnesium deficiency, but why would the plants be deficient in anything when I just transplanted them in new soil in March? Because the chelated iron had such an awful and pervasive effect even on leaves not yet showing damage, and that garden centre people were sure it was an iron deficiency, I'm reluctant to guess and do more harm. Is there a way I can test for what the problem is? The link suggests that the nutrients might be present but the PH level in the soil doesn't allow the plant to take them in. Is there a reliable way to test PH levels? Interested in all opinions and insights ....
Assuming that 'new soil' contains enough of the nutrients your citrus plants require would be a big mistake. The concept of 'soil' is open to so many interpretations, you absolutely cannot count on anything. What is 'soil for citrus' in the first place? I'd be suspicious of any nursery that uses such terms. I worry that you are overthinking this. It's probably too late in the year now to make any changes. If those were my plants, I'd give them more nitrogen as winter ends and observe how they respond. @Will B from the Victoria area grows and is very knowledgeable about citrus. I hope he replies to this post or that you can contact him.
The two fertilizers you have been using contain micronutrients so it would be safe to assume that if there is a deficiency it is not in micronutrients as they are only needed in small amounts. The recommendation to treat the trees with chelated iron seems unfounded. I do not believe there is a magnesium deficiency; there is no sign of the tell-tale V-shaped area on the leaves. I stand by my recommendation to switch to a fertilizer with a formulation that is more suited for citrus. There is no harm in doing so and any deficiencies will be resolved over time. This seems a better solution than in trying to diagnose the exact deficiency. Also, the use of a high-nitrogen fertilizer will have the effect of lowering the soil pH which is beneficial for citrus. This should address your concern wherein higher pH levels inhibit the update of certain nutrients. You may want to look at the following thread. Note in particular the comments relating to organic fertilizers: Fertilizer for indoor dwarf citrus? It's not a good idea to apply large amounts of fertilizer this late in the year so opt for application at half the recommended rate until warmer weather arrives in the spring. Other thoughts: The leaf seen in IMG_1909 is interesting. Note the dark green mid-vein. I wonder if this is a sign the tree is making use of the recently added nitrogen. Perhaps the low amount of nitrogen in the fertilizers and that fact that they're organic accounts for the slow improvement. The medium sold as 'citrus soil' is probably not that suitable. It's likely to be not porous enough but that's another story.
Thanks very much, I am going to try this idea. I didn't know that nitrogen will raise the ph too, which would be good to see if that helps things along. Should I keep fertilizing at half strength, maybe a month apart, throughout the winter or should I stop before the first frost date? Side note re: the citrus soil, as I remember it, was quite loose with lots of bark, peat, loose soil, good drainage, but my plants do dry out very quickly. They'd been in a heavy, hard clay-type soil at the nursery and I wanted to get them out of that, it didn't seem to drain well because the water would pool and sit at the top. I have two other citrus trees - not photographed - on the other side of the balcony, I kept them in the soil they came in and they don't have the same issue, so you may have something there...
I think the other comments provided so far are all on the right track. The photos do show signs of insufficient nutrition and the symptoms do correspond to a lack of nitrogen, manganese, and possibly zinc. When there are insufficient nutrients citrus tend to make the older leaves senescent and they will deteriorate until they fall off, a process that is difficult to stop once it starts. Nutrients take quite a while to correct symptoms, so patience is needed to see if what you did was sufficient. Citrus are heavy feeders and to have the lush dark green leaves they need plenty of nutrients, particularly nitrogen. The fertilizers you mention using have very low levels of the three main nutrients. The three numbers provided are percentage of each of N-P-K, so 3-0-4 that you mention first is only 3% N, 0% P, and 4% K. You would need to provide quite a lot to satisfy a citrus plant. Miracle-Gro at 24-8-16 provides a lot more nutrients if you use a similar amount, it provides many of the micro-nutrients needed as well. This is very helpful since adding micro-nutrients can be tricky for a beginner. Providing too much of certain micro-nutrients can create toxicities that are difficult to correct. If adding the treatment they gave you made things worse then I would stop using it, at least for now. To get faster results you can try feeding the leaves directly using a foliar fertilizer. This also tends to slow leaf senescence if you are trying to do that. Miracle-Gro works fine as a foliar fertilizer as well. Mix it at regular strength (or less if you prefer) and mist the leaves with it. Be sure to apply the misting all over the plant, including the undersides of the leaves.
Hi Will, thanks for your reply. I just checked my chelated iron product and it contained manganese and zinc was well, so I guess we can eliminate that possibility and conclude it must be the lack of nitrogen. I will get that Miracle-Gro and try the foliar feeding idea. The plant is not really dropping many leaves, and what have fallen I think is just the normal occasional drop that comes in cooler weather. The plant that is worst-afflicted really didn't put out much new growth this year, it just flowered and fruited well, and the fruit is still holding on and looking good, but the lack of new growth this year was concerning. I suppose that also could be due to lack of nitrogen. I was thinking of adding some worm casings - do you think that's a good idea? I read that they help bring micronutrients into the soil as well.
Does this issue affect only older leaves or all leaves? One possible cause can be salts accumulation in the soil (too much fertilizers). Citrus and Salinity - Citrus Industry Magazine I amend the soil in my citrus pots only once or twice a year, with very small amount of fertilizers. My citruses are lush and healthy. I'm using mineral soil (from my garden bed) in containers. If it was peat, then I would needed much more sophisticated care for my trees.
Too much salt in the soil (or water) causes edge and tip burn on the leaves, it is quite distinctive. There is no sign of that in the photos.
My trees are in a semi-outdoor location and are fertilized at half strength through the winter. Leaves showed signs of nitrogen deficiency when I didn't fertilize at all. In addition to Miracle-Gro mentioned earlier you could also use PlantProd 30-10-10. The medium that you have now sounds like an improvement over the clay mix you had before. Soil mixes typically sold at garden centers are too dense and need to be supplemented with bark chips and perlite.
You are right that cooler weather interferes with nutrient uptake. It is a bit early for the cool weather to really impact citrus in our area though. I am not seeing any cool weather impact yet in my collection. I have heard worm castings are good, but have not used them myself.
Hi Sulev, it was all on the lower (older) leaves until recently, and since the iron treatments has travelled all the way upwards, except that the new growth (very little) is not affected and still is green. As for the salts, a few years ago I saw that with some other plants I had, white rings of salt on the terracotta, but haven't seen anything like that since then. There's no burn or brown tips either so I think we can rule that possibility out, thankfully.
I found the composition of the citrus soil mix I'd bought and transplanted the trees into in the spring: It's got blond peat, composted bark, volcanic ash, vegetable compost, manure and marine algae. I also put clay pebbles at the bottom and a bit in the soil too for drainage. On another topic, when you say you fertilize half-strength throughout the winter, do you do that once a month? More? Less? For reference, in the summer, I was doing half-strength every two weeks, though as someone pointed out that probably was not enough considering the low percentages of NPK. Previous seasons I did nothing in the winter at all because I believed it's dormant so not supposed to. It makes sense to feed it, though, since the fruit continues to develop. Last two years, the lemons were ready in January/February. This year, they look ready just about now. I've got more photos, taken today. For the last 2, the yuzu, you can see the negative effect that chelated iron treatment had ... most of the plant is still a beautiful deep green, and where the yellowing is, that didn't start showing up until the iron was introduced. I sure appreciate your collective wisdom and goodwill so far!
This is consistent with nitrogen deficiency: Nitrogen (N) for Citrus Trees. You may want to forgo doing so in the future: The Myth of Drainage Material in Container Plantings (pdf). @Sulev has a different opinion in this regard. Fertilize at half the strength prescribed on the label. More frequent feedings of this amount would be better for the tree so it could be done twice a month at quarter strength.
You may want to look for signs of improvement after the first couple applications. If the tree is active and making use of the nutrients, areas next to leaf veins should become greener, otherwise you may want to discontinue the feedings until warmer weather arrives.
Got it, thank you. I've given an application a few days ago and will watch things and let you know. It's good to have had some photos and as long as I don't change the plant position (and I don't plan to), I should be able to compare apples to apples, or rather lemons to lemons :)
