Watering Pelargoniums

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Watering geraniums

Pelargoniums (commonly known as geraniums) have a reputation as hardy plants that don't require much love. While it is true that they will usually survive all manner of neglect, one thing you do have to get right with them is watering. And the surest way to kill a pelargonium is to consistently give it too much water (this can lead to root/stem rot which is impossible to recover from once the plant has been infected). On the other hand, it is also possible to go too far in the other direction and not give them enough. So how do you know how much to water your pellies? And what are the signs of over-watering and under-watering?

WHEN TO WATER

It is more difficult to know when a pelargonium requires water because, unlike many other plants, their leaves typically do not wilt when they get too dry. Sometimes people go ahead and water just because they think that surely the plant must need it by now, but this is not necessarily the case for geraniums as they are a plant that can survive on very little water indeed. They like to dry out almost completely between waterings, and then get watered deeply. It is important to assess your pelargonium first, before watering on a guess that it might need it. It also matters whether your pelargonium is in a small pot, a large pot or in the ground when making this assessment. Let's look at each of these individually. 

Small pot. I define a small pot as one that you can easily lift with one hand. Pelargoniums in small pots are the easiest to assess for water requirements (especially if the pot is plastic). Simply lift the pot up and feel the weight of it. You need to know how heavy it feels when it has just been watered, but once you know this, you can assess if it feels comparatively light when you pick it up. If it does, it needs water. If it still feels reasonably heavy for its size, it does not. This is something your hand gets better at assessing with practice until it becomes almost muscle memory. Beginners might like to get two dry pot plants of the same size, water one but not the other, and then lift up each pot in one hand. The difference in weight will be fairly significant and will give you an indication of what you're looking for. 

Large pot. Once a pot is too large and heavy to easily lift with one hand, a different method is needed to assess water requirements. I have often read advice to feel the top of the soil - if it is dry, water, if it is moist, do not. I have to say that this is bad advice for pelargoniums. The top of the soil is not where the roots are located, and what matters to pelargoniums is how wet they are lower down. You need to stick your finger in much further to get to the part of the soil in which is the main root ball, and for very large pots even this won't do. For a very large or tall pot, it is best to use a soil moisture meter - stick it deep into the soil where the roots are, wait the specified amount of time, and read what the gauge says. Water (or don't) accordingly.

Moisture meter checking water needs of a geranium
The moisture meter is indicating that this plant is already wet - therefore best not to water

I have to admit that I am usually too lazy to do this, though it is the only way to surely know whether your large pot plant needs water. I prefer to rely on the passage of time and what the weather is doing to gauge when to water my pellies in large pots. In summer (day temperatures low 30s to 40°C), I water them once a week. In winter (day temperatures mid teens to around 20°C), I water 2-3 weekly. In spring and autumn (day temperatures low to high 20s) it is about 10 days to 2 weeks between watering, depending on how warm the weather has been. I have worked out through trial and error that this is about how often to water my particular plants, always keeping an eye out for signs of over or under-watering and adjusting my watering schedule accordingly

In the ground. My pelargoniums in the ground get watered by twice-weekly reticulation from 1st September to 1st June and by rain from 1st June to 31st August (due to reticulation restrictions). It is much more difficult to control the amount of water your pelargoniums receive when they are out in the garden and exposed to all the elements and timed reticulation. However, in the area that I live (Western Australia), the soil is very sandy and and well-draining and pelargoniums do quite well planted in it. I have never lost a pellie planted in the ground due to over-watering for this reason and I don't do any hand watering either. If you did want to control the amount of water your pelargonium in the ground was getting (if you have a garden bed under the eves or a verandah for instance), I suppose that you would use the same technique as for a large pot - sticking your finger as deeply as possible into the soil to determine moisture or using a moisture meter. 

HOW TO WATER

The most important thing is to water deeply. Allow your pelargoniums to dry out almost completely and then drench the soil until you can see water coming out of the drainage holes at the bottom of the pot. The other thing I do to really make sure the pot has had a good drenching is to lift it afterwards and feel that it is heavy. If I don't think it feels heavy enough, I keep watering until it does. For my large pots, I will give them one watering and then come back a few minutes later and give them a second to ensure that all of the soil is really soaked.

Over time, soil can become water repellent, especially if you tend towards under-watering (like I do). This means that the water has a tendency to run off the soil rather than soaking into it, and it has an effect on how long it takes to properly water your plant. You may see water coming out of the drainage holes of the pot quite quickly, but if the soil is water repellent, it could be that it is simply running across the top of the soil and then down the space between the edge of the soil and the pot (refer to diagram below). This means the top inch of the soil will be wet but the rest of it (i.e. the root ball) will still be dry.

Diagram of what happens when you water very dry soil


The major sign that your soil is becoming water repellent is when you water your plant and the water always takes a long time to soak in, just sitting there in the top of your pot. If you notice this, I would recommend using a soil wetter to remedy the problem.

It is best to avoid overhead watering with pelargoniums, as they do not like getting water on their leaves (especially if it sits on them for a long time) because it encourages fungal diseases. Try to water the soil at the base of the plant instead, and do it at the beginning of the day if possible so that any water that does splash onto the leaves has time to dry in the warmth of the day. 

OVER-WATERING

It is important to always be on the look out for signs of over or under-watered pelargoniums so that you can adjust how often you are watering before any permanent damage is done. Let's start with signs of over-watering.

The leaves feel limp or appear wilted. I said earlier that pelargoniums are different to many other plants in that their leaves do not wilt when they need water. The opposite is in fact true - wilted or limp leaves are a sure sign that there is too much water in the soil the pelargonium is planted in. Allow the plant to dry out before you water it again, and then reduce how often you water it thereafter.

The leaves are yellowing and dropping off, yet when you stick your finger into the soil, it is wet. The confusing thing about figuring out whether a plant is over or under-watered is that the symptoms are quite similar. Both under and over-watering lead to yellowing leaves that drop off. However, the difference can be determined by feeling how wet the soil is when you notice the symptom. The other difference is that in over-watered plants there will be a lot of leaves falling off and it will be happening to young and old leaves alike. 

Over-watered geranium
Example of yellowing, wilted leaves on an over-watered geranium
(Photo credit to Kylie Goater)

The plant is looking generally unhealthy and there are no signs of pests that could be responsible for its condition. If your pelargonium suddenly starts to look poorly, check the soil first - if it is wet, chances are you are over-watering it. Then check the roots - if they are still white, it means they are still healthy and there is hope. Allow it to dry out, then resume a less frequent watering schedule. 

You notice what look like tiny black flies flying out of the plant when it is disturbed. These are called fungus gnats, and they thrive in soil that is perpetually moist. I have had these before and they did not appear to do any damage to my plants, but they are a nuisance. Drying out the top inch or so of soil (where they lay their eggs) should get rid of them. It is not always the case, but it could be that if you have fungus gnats in your plants, you are watering them too much. 

There are raised, corky brown spots on the backs of the leaves. This is called oedema, and it occurs when the roots have taken up more water than they can use and the cells in the leaves burst because they are too full. Ivy pelargoniums are particularly prone to oedema. If you notice a lot of leaves have it, it means back off on the watering!

Oedema on an ivy geranium leaf
Oedema on an ivy pelargonium leaf

The stem feels squishy. This is a bad, bad sign and unfortunately means the plant is beyond help. When a pelargonium is sitting in too much water for too long, its roots will start to rot. Then the stem at the base of the plant will start to rot, causing it to feel squishy rather than firm and eventually making it turn a black colour. Over time, this rotting will move up through the whole plant and cause it to collapse and die. If you have a squishy, black stem on one of your pelargoniums THROW IT AWAY!!! There is no hope for this plant.

Black stem rot on a regal pelargonium
This regal pelargonium has signs of overwatering - note the yellowing leaves and black area at the bottom of the stem


Black stem rot on a regal pelargonium
When taken out and examined, it is even more evident that the stem on this pelargonium has black rot - time to throw it away

It smells bad. Rotting roots are caused by bacteria that thrive in perpetually wet soil. This rotting produces a smell and it is a bad one (hard to describe but you'll know it when you smell it). Last winter I discovered one of my Big Red geraniums was sitting in an inch of water at the top of its pot. Upon inspection, I realised that its drainage holes had become blocked with roots and so the water had nowhere to drain. It was rotting and smelt bad, bad, BAD. I had to hold my breath as I disposed of it! 

UNDER-WATERING

Next let's look at the signs of under-watering. Pelargoniums tend to cope much better with under-watering than over-watering; they just won't grow as quickly or produce so many flowers - a consequence that most of us would prefer to avoid! My tendency is to under-water my pellies, as I am paranoid about over-watering and causing root rot, so I have become quite familiar with the symptoms...

The lower/older leaves go yellow from the edges and eventually drop off. I mentioned earlier that yellowing leaves can be a sign of both over and under-watering. If the plant is under-watered however, these leaves will feel dry and crispy instead of limp (as in the case of over-watering). There should be less of them too (unless the plant is very parched) and the older leaves will be affected first and the newer ones last. Lastly, when you check the soil of a pelargonium that has yellow leaves, it will feel very dry if it is under-watered. These things mean you should water the plant straight away, and perhaps don't wait so long until you water it again next time!

Ivy geranium/pelargonium showing signs of under-watering
This is an example of an ivy pelargonium that has been allowed to get a bit too dry. Notice that the older/lower leaves on it are starting to go yellow from the edges, and there are a couple that are completely yellow and will fall off soon.

The buds dry up. This is the symptom that breaks my heart! When I have been under-watering my pelargoniums, I notice that the new buds on them have dried up due to the lack of water (sob, sob). Once a bud has dried up, you can't get it back, but you can get the plant to make new buds by watering a bit more regularly in future!

Dried up buds on ivy geranium/pelargonium due to under-watering
Two examples of new buds that have dried up due to lack of water

It takes longer to water the plant because the soil is so dry. When you allow soil to become very parched, it struggles to absorb water at first. You might notice that you pour water onto it and it just seems to sit there for a while before it is eventually absorbed. In this case you must be careful to water thoroughly - you may need to leave the water to soak in for a bit and then come back and give the plant a second soaking. It may also be beneficial to use a soil wetter if it is a recurring problem.

Growth is stunted and slow. Under-watered plants do not thrive. They take a long time to put on new growth and flowering is reduced (if it occurs at all). If you notice that this is the case with your pelargoniums (particularly if they have other symptoms of under-watering), consider your watering schedule and whether it is possible you haven't been watering enough.

THAT'S ALL, FOLKS!

I have told you everything I know about watering geraniums/pelargoniums and how to tell if you are watering too much or not enough. If there is anything else you can think of on this topic that might be helpful for pelargonium growers to know, please put it in the comments section below!




8 comments

  1. If I ever get a garden again (I live in hope.......) I will definitely be bookmarking this post for all the best geranium-watering tips!! You have a lovely collection of geraniums in your garden, so I know I can rely on you for the best explanations and tips when the time comes xx

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    1. You'll get your garden back! And then I can give you some lovely geraniums to put in it :-)

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  2. This is a wonderful blog Hannah. I will reading this lots of times to work out what is wrong with my plants. Need to retire then I can devote more time to them

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    1. Thanks Pauline, a lot of gardening is trial and error so it's great when you can read something that helps prevent some of that error! I know what you mean about retiring - I'd love to spend more time in the garden as well but alas, my 2 year old and bub on the way won't allow it. Good thing I love them so much :-).

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  3. And this explains why I'm such a useless gardener - it involves way too much care and attention for my limited supply :) I always assumed geraniums were easy to care for - now I realize it's quite a scientific process!

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    1. Nooooo don't come to that conclusion! It sounds harder than it is and if you only have a couple of geraniums you would be fine - the main thing is not to water too often, crazy geranium people like myself kill our plants with too much love. Neglect they can handle much better :-). Xox

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  4. Hi Hannah, I used to garden many years ago, when I was in another city. May be I would resume sometime. This is a wonderful blog post, which will be of great benefit.

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    1. Glad you found it helpful :-). I find gardening very therapeutic and there's always lots to learn!

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