Hello everyone Having a few issues with Lemon trees. One of which is with my Eureka lemon trees I recently bought. They're only about 1m tall with plenty of green leaves. For all intents and purposes, they look pretty healthy. I potted them up shortly after arriving, so they are in their original potting mixture plus a little generic compost so I think they have the right nutrients. I check the soil regularly, and water only when necessary. The soil is just slightly damp. Checked for signs of citrus leaf minor, or red spider mite. Nothing. And yet.............the leaves are all slightly curved. In some cases twisted. Not sure if this is a winter thing or them suffering some kind of disease or pest. I have moved them around the house to see if it makes a difference but it doesn't.
Some leaf curl in citrus is quite common, particularly in fall and early winter. There are lots of different possible reasons I have read about and seen: too much fertilizer, nutrient imbalance between nitrogen and potassium, too little water, too much water, changing temperature and conditions that happen in fall and winter, leaf miners and other pests. It seems to me like you have already checked for the more problematic causes that would require action. Looking over the photos the leaves look fine to me and the slight curl is probably due to changing conditions. New growth will most likely be fine.
Just out of interest, I've seen a couple of comments about leaf curl in fall and early winter. Is this light / temperature related? Given that the plants have been indoors at around 20C (68F) in a centrally heated home the whole time. Presumably it's more of a light thing? I guess the other alternative is that the plants were quite happy at the nursery where I bought them, but got shocked in transit. One was broken, but in these photos, with the plant straight out of the box on arrival, you can see the leaves already a bit curved
My theory is that leaf curl that is not caused by pests is due to a moisture (or nutrient) flow imbalance of some kind. Too much moisture and they curl one way, too little and they curl the other way. When conditions change (humidity, temperature, light) they are likely to cause a moisture imbalance due to the rate the plant transports moisture to the leaves vs how fast the leaves use it. Depending on how much and how fast conditions change it could result in leaf curl, leaf loss, or both as the plant tries to adjust. The next flush of growth occurs after the plant has adjusted and so looks just right.
The plant is turning leaves inward and under in order to conserve moisture and reduce its profile (heat catching surface area). It is an indication there is a high transpiration rate and you need to raise the humidity to lower the VPD and bring the transpiration rate to a healthy condition. If you can't raise the humidity you can lower the air temperature. As a reference point, I was in a citrus growers nursery today and they are running 77F and 60RH. When they water the humidity would be higher. I use humidity trays filled with lava rocks at the base of my citrus to increase humidity. Potting them up can also be a big issue. Citrus likes to be root bound and when they are watered the like to be watered evenly. If they are transplanted into a pot that is too large half the roots will be dry and the other half wet. VPD Calculator by Everest Fernandez
