How We Avoid Over and Underwatering Our Potted Citrus Trees

Underwatering and Overwatering Symptoms Are Often Similar

If you've had potted citrus trees for a while, odds are good you've experienced both underwatering and overwatering symptoms. But if you haven't, we'll make a complaint that every tropical fruit tree grower has at one point or another- the symptoms often appear to be the same!

Citrus trees that are overwatered can exhibit a number of signs, such as drooping or discolored leaves, loss of flowers, fruit drop, mold growth, and pests. Conversely, citrus trees that are underwatered show many similar signs, like drooping leaves, discolored leaves, loss of flowers, and fruit drop. Telling the difference becomes rather difficult in the early stages, and I often can't tell whether I've underwatered or overwatered until they reach an extreme level where the tree is close to death, when more severe symptoms develop (such as dry trees getting crispy leaves, excessive underripe fruit drop, or wet trees getting moldy).

Yes, it really can be that hard to tell the difference!

I could likely dedicate an entire article to all the issues that underwatering and overwatering have on tropical plants, about their influence on nutrient uptake, what happens if the roots rot, and the like. But for this one, it's more important to simply state that both underwatering and overwatering can share many similar symptoms.

Instead, I want to focus more on how we identify when citrus trees need water. The simple truth is that unless you have a really good watering plan in place, you could very well be alternating between both conditions- for the longest time, I absolutely was!

You May Alternating Between Conditions Without Knowing It

One of the biggest frustrations of growing citrus trees (and, really, any tropical tree) in a container is finding the balance between overwatering and underwatering. To make matters worse, as you may have guessed from some of the above commentary, the way your tree responds to both extreme cases can often look the same. As such, it is rather easy to swing between overwatering and underwatering if you're not careful.

To say these trees are particular is an understatement, and it took me several seasons to begin to truly understand their water requirements in pots. 

The general consensus with tropical fruit trees is that you need infrequent, deep waterings, and not to water again until the top 2-3″ of soil are completely dry. Most guidelines say to add water until excess starts to come out of the pot, which you can see accumulating in your drip pans when indoors. Water until you see this, wait a period of time (often days or weeks, depending on conditions), check to see if they're dry, and water again.

Using this method, I found that my trees would dry out quickly. Whoever said “weeks between watering indoors” clearly never saw my trees, as in many waterings they'd be bone dry within a few days (and, yes, I run a humidifier and don't keep my house warm!). Big ones, small ones, more light, less light, close to humidifier, far from humidifier- didn't matter, they all seemingly dry out fast most of the time. Even with a full drip tray after watering indoors, I would regularly see them suck that water back up into the plant within a day or two and dry out fairly quickly. If I missed watering again, underwatering symptoms would appear.

But there were also times when these trees did not dry out within a few days, and the opposite problem would happen. I'd water deeply, the drip pan would fill up, but for some reason, the water would stick around. In extreme cases where the water sat for quite some time (read: a week, rather than just a day or so), overwatering symptoms would begin to appear– particularly if I continued to keep watering such that the drip pan was always full. 

It wasn't until I really started to pay close attention that a trend began to emerge. So, herein lies my theory of what is going on, and what I am starting to look for when watering my citrus trees.

What To Look For When Watering Citrus Trees

Based on my observations, I would theorize that a single deep watering of potted citrus trees may not be sufficient when they are fully dry. Yes, you should add water until you start seeing excess come out the bottom. But seeing excess does not necessarily mean the tree has been properly watered- at least, not to the point that it can be forgotten about for an extended period before watering again.

In my opinion, this might be due to the quick-draining soil types that these trees prefer.

When you water, you balance the amount needed for the tree to stay hydrated with the soil's capacity to hold water. When the tree dries out, as recommended between waterings, I suspect that the soil becomes a fair bit more porous, allowing water to reach the drip pan more quickly than when it is saturated. (You may notice how the soil feels different when checking for moisture with your finger, too- wet soil and dry soil feel way different.)

You may think you've watered enough because water is visibly passing through, but in reality, it may be partly because the soil is still on the dry side and is simply letting it pass through. This is one possible explanation for why sometimes water is sucked back up into the plant in a day or two- the soil may be telling you that it was not fully hydrated. If you stick with this schedule and wait a fair bit of time before your next watering, your tree may start showing signs of underwatering conditions. 

What I've noticed here is that if I water again once the drip pan dries out a day or two later, watering deeply so the water passes through and refills the drip pan, the plant seems to stay hydrated for quite a while. Not a day or two, but a week or longer- the soil is telling you that it is now sufficiently wet, but possibly also could be too wet. If you keep watering frequently here, you may risk overwatering damage like root rot, attracting pests, etc.

So my current watering schedule is an attempt to balance both of these.

The first step I take is to let my trees dry out as best as possible. Here, I do a mix of checking the top 2-3″ inches of soil to make sure it is dry, but I also have a good feel of what the weight of the pot/plant is when dry vs when water is present (it is a fairly noticeable difference). If you don't lift your plants up regularly, get in the habit of doing this because if they're anything like mine, you will notice a fairly significant swing in weight depending on the pot size.

Once I am happy that the plant is sufficiently dried out, I give it a deep watering until I start to see liquid accumulate in the drip pan. If any tree sucks up that water in a day or two, and most often do, I treat that as a sign that I may not have watered enough, as my theory suggests the dry soil is letting water pass through too quickly. I then do another deep watering until I start to see water accumulating in the drip pan again.

One observation I made here is that during the first watering, excess water would quickly flow into the drip pan (i.e., a few seconds later). The second watering would be fairly delayed by comparison (i.e., up to a minute or longer). Here, you can run the risk of truly overwatering, so I am a fair bit slower adding water to try and get the plants to minimize how much accumulates in the drip pan. Seeing a bit of water the second time is good. Filling the pan completely, not so much unless I'm leaving the house for a short period of time (say, under a week away).

• When I go away longer than a week, I tend to add Blumat self-watering stakes into the soil, fed from nearby buckets of water. We'll publish a full review on this one later, but one thing worth noting is that these likely work via osmotic pressure differences between the water in the cone and the moisture in the soil. I have better luck with these when the soil is very well hydrated at the start, rather than in the underwatering condition discussed above. 

When using this watering setup, I've noticed that the soil stays hydrated for much longer, and my indoor watering intervals shift from days to weeks, as is often noted in most best practices. Then I go back to checking soil conditions over time by lifting the plants and checking the top few inches of soil for dryness, letting the plants dry out more, and repeating the cycle when needed.

Is this a better method for watering potted citrus trees? Honestly, right now I don't know. But I do think that it has limited the visible underwatering and overwatering conditions I've seen in my own trees in the past. So for now, I'm sticking with this and will revise if (or when) that time comes.

• Final caveats: As with everything, watering intervals are best done on an as-needed basis, not on any set schedule. Even with my observations above, if my plant feels light and dry, I water, and that's that. If anything, the above commentary is only an observation on why my plants sometimes dry out in a few days vs. why some dry out over a much longer timescale when indoors, and how I'm trying to get to a more consistent watering schedule. But, at the end of the day, your soil is the ultimate guide- so check your plants regularly!
• Likewise, I don't necessarily think it is bad if my plants dry out and need watering every few days indoors, even if conventional best practices suggest it should take longer between waterings. Going dry is fine- staying dry for a long time is not. That said, part of the reason I looked into this more is that I also travel a fair bit, such that having a more predictable watering schedule helps immensely when I can't check them every few days. One time, I watered my plants really well, went away, and they were fine many days later. Another time, I thought I did the exact same setup, went away, and many were severely dehydrated when I returned to the point that I thought they were about to die. Part of figuring out an ideal watering schedule was to replicate the former scenario when I cannot check my plants regularly.
• One final reminder- this is all just a theory. Your mileage may vary. Let your plants be your guide! 

Do you have any special things you look for when watering a potted citrus tree? Comment below to share!