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Now, before we start, I don’t want anyone going home from this blog post (as it were) and thinking they’ve been watering their plants wrong.
As long as you regularly apply water to your plants, that’s plenty good enough for the majority of house plants.
They’re not bothered where their water is administered from as long as they get some.
Even plants like African violets, which everyone says to bottom water, are perfectly happy to be top watered. A plant that will suffer if it get wet will not last long on this earth.
There are definitely pros and cons to each method, and the way I water my plants depends on a variety of factors, such as the plant, how much time I have, how arsed I can be, and how sick I am of fungus gnats at the time.
What is top watering?
Er, it’s when you water a plant from the top. You get some water, a watering can (or old teapot in my case), push the spout into the leaves so it’ll hit the soil without sending it everywhere and apply water.
Make sure the top of the soil is thoroughly saturated and keep going until the water runs out of the drainage hole at the bottom. (Don't have holes in your pots? Read this article to find out why that may not be a good idea)
Leave the water to drain away.
Don’t allow the plant to sit in the water – it can cause the soil to get too wet and potentially lead to root rot. I water my plants over a pot like this:
This is especially good if you don’t want to waste any water or fertiliser. I’ve never had an issue with reusing water.
Top watering: pros
This is the number one reason that I top water when I do.
I sometimes bottom water, but if I see a plant that needs watering urgently and I’m pressed for time, I just give it a thorough soaking and leave it on the draining board to tend to when I can.
It may seem like a bit of an overdramatic statement – if you’re looking after your plants well surely they shouldn’t need watering so urgently?
That’s true in a lot of cases – plants starting to droop will be fine for a while until you have time BUT some plants, particularly alocasia, are considerably thirstier when they’re putting out a new leaf.
They could need watering every other day, so it’s easy to let that slide. Unfortunately, if they don’t get the water they need there’s a chance that leaf won’t develop properly.
Some plants just droop so dramatically (Oxalis, peace lily, and Marble Queen pothos, I’m looking at you two) that I feel bad leaving them.
You can literally wash pests away when you top water – any eggs that are developing in your soil, or larva, will be sent down the sink.
Just don’t have this be your primary reason for top watering.
Top watering can also increase the number of pests and the likelihood you’ll attract bugs like gnats in the first place, so it’s all just swings and roundabouts really.
Reduce mineral deposits
Over time, salts and mineral deposits will build up in your soil. If you have terracotta pots, you can see the salts building up on the sides of the pots.
These often come from the fertiliser you use and the water- those of us that live in areas of hard water will probably see more, and it might be an idea to either collect rainwater or use a water filter.
When you top water your plant thoroughly, salt and minerals are washed away.
If you have brown leave tips (read all about the causes in this post), it can be caused by a buildup of mineral deposits in the soil.
As I mentioned before, I often reuse water that’s run off other plants, and I’ve never had an issue with buildup in the soil. You can check your soil’s ok by checking the pH.
The plant is thoroughly soaked
Provided you thoroughly and properly water your plant, you know that every inch of the soil will be wet.
Well, more or less.
Be aware that soil can become hydrophobic over time, and won’t absorb water – the water runs through any available cracks and out of the holes in the bottom of the pot. Bottom watering a plant for a few hours is a great way to make a plant, er, unhydrophobic,
Top watering: cons
There are two pretty big downsides when it comes to watering houseplants from the top. HOWEVER, neither of these things is particularly life-threatening to your plants (apart from under pretty specific circumstances, which we’ll get to in a bit).
Top watering can cause damage to the leaves
A lot of plants have leaves that don’t want to get wet.
However, this isn’t usually much of an issue because, in the wild, plants would have to deal with rain.
Rain doesn’t try to avoid plant leaves AT ALL, so plants have learnt to adapt to occasionally being rained on without dropping leaves immediately.
As I mentioned above though, there are certain plants like African violets that would prefer not to get wet. That doesn't mean you can't top water them - it just means you should avoid getting the leaves wet OR dry them off with a paper towel after.
Top watering can encourage fungus and pests
I saw a major decrease in fungus gnats when I started bottom watering almost exclusively.
Fungus, fungus gnats and mould love damp conditions. I've found that by keeping the top couple of cms of soil dry really hinders any pest production.
Again, top watering exclusively shouldn’t cause an epidemic of fungus or associated pests – it’s often a sign of a larger issue (often, you guessed it, overwatering).
However, if you have a significant number gnats trying to climb into your wine glass (they bloody love prosecco) but you’ve not got a massive infestation, bottom watering may solve your problem.
Well not solve, because fungus gnats are nigh on impossible to eradicate, but at least keep numbers low.
Ok, let’s move onto bottom watering. We’ll take this opportunity to laugh at the word bottom because it’s funny, and then we’ll grow up and move on.
Top watering can cause the sool to get compacted
Water is heavy. If you regularly pour a lot of it on top of soil it can cause it to become compacted, which is bad for a couple of reasons:
- Water always looks for the easiest route through the soil – if the soil is very compacted then it’ll run down the gap between the soil and the side of the pot, rather than evenly through the soil
- It can cause root damage. Roots tend to like a bit of air movement around them, so they can become damage (or even begin to rot) if the soil becomes too compacted.
If you’re worried about compacted soil then there are a couple of steps to take:
- Use a fork (or moisture probe) to GENTLY churn up some of the potting mix
- If the potting mix is fairly heavy (which most commercial ones are) then repot your plant in a mixture of your regular potting soil, perlite, and bark chips. I use 2 parts house plant potting mix to one part each of perlite and bark chips.
Don’t worry too much about soil compaction if top watering is all that’s available to you – just make sure you have a nice, airy soil mix and give it churn up every now and again.
If you’re interested in learning how to make your own potting mix, I have a recipe in this post. As well as reducing soil compaction, homemade potting soil is great for growing stronger roots, and it’s peat-free and has less impact on the environment.
What is bottom watering?
Well, would you believe it’s watering your plants from *drumroll please* the BOTTOM! Not the TOP, the BOTTOM.
How you bottom water?
There are a couple of methods to use, depending on time, laziness and the plant in question.
The easy way, for the time poor
Make sure all of your plants have a) a drainage hole or two in their pots and b) a saucer under the said pot in which to put water.
Fill the saucer with water. Wait for the saucer to empty. If the plant drinks it all within a few minutes, fill it up again. If you’re unsure if the plant’s had enough water, poke it with your trusty moisture probe. Or finger. Or just keep topping it up until the water’s no longer draining.
The also easy, but more time-consuming way
This method is best for ensuring everyone gets a good soak, but it can be time-consuming and a bit of a faff.
Fill a big tray with water and er, put your plants in it. That’s it.
Some people fill the bath and I can see the benefits – people unlike myself that have a normal amount of plants could probably get their whole collection in the bath at once – soak for an hour and you’re done.
I however, have many bath’s worth of plants, and a lot of them are too awkward to put in there – my aloe vera literally wouldn’t fit, my fern’s leaves would fall in the water, and all my little pots would fall over.
So I just use an old rabbit litter tray.
There are certain plants I water almost exclusively by soaking them – my Boston fern (the asparagus fern is pretty drought resistant, so I just fill his saucer) and my orchid.
I’m not great with orchids so I took it out of the substrate and keep it bare root in a jar. I soak it weekly for an hour. It bloomed!
Bottom watering: pros
The leaves don’t get wet
If you have plants that have fallen victim to overwatering in the past and have the scraggy leaves to prove it, then bottom watering maybe your friend.
As I mentioned before, certain plants like African violets are a little averse to getting their leaves wet and suffer water damage easily.
Cacti will rot quickly if they’re regularly covered in water, especially in the colder months. Wet leaves are fine, but they can’t stay wet for long, otherwise you end up with fungus and rot.
The top of the soil stays dry, so you get fewer gnats
We’ve already talked about this. Pests like the damp.
Even pests that prefer a dry environment, like spider mites, won’t be put off by wet soil.
Encourages the roots to spread out
When the roots of your plants have to work to find the moisture, then it can help them to grow stronger and grow towards the bottom of the pot.
In the case of plants like cacti and succulents, this mimics their natural condition – they often live in places with little rain – their roots have to grow towards the groundwater.
Bottom watering: cons
Mineral deposits can build up if you only bottom water
If you never flush your plant through with water from the top, it can be easy for mineral deposits to build up in the soil. This can result in the delicate roots of your plants being burned.
If this is something you worry about (say, if you use tap water and it’s particularly hard) then just set yourself a reminder to top water everyone every three months or so.
When you fertilise your plants, it might be an idea to top water your plants every time you feed them, so that you associate the two things with each other and are less likely to forget.
It’s a logistical nightmare for big plants
It can take AGES for big plants to absorb enough water, especially if they’re in terracotta pots.
I have a couple of palms that I top water but they’re in such big pots they only need watering every other month.
My golden dragon philodendron got stood in the water tray in the kitchen where he gets in everyone’s way. He’s since upgraded to a self-watering pot.
It can take longer
Well, depending on your setup.
If you only have small saucers then it can be time-consuming to go around topping them up, and then emptying them when the plants have had sufficient watering.
If you use cachepots, you can just fill them up with as much water as you think they need. In the beginning, you’ll need to go round and empty all the standing water, but once you’re accustomed to what you’re doing, you’ll be better able to judge how much water each plant needs.
For many of my plants, especially cacti, I use 24cm terracotta pots, and instead of saucers I use £2.50 white pasta bowls from Wilko. They look pretty good and if I fill up the bowls about three quarters that seems to be the ideal amount of water for the plants.
It can be messy
If you’re moving plants back and forth into soaking trays then you’re bound to get either water or soil (but probably both) on the walls or floor (but probably both) of your home.
I’ve set up a little watering station in my kitchen – I keep a tray there, filled with rainwater. It’s always at room temperature (I top it up before bed when it starts getting empty), and I just put dry plants in there.
When they’re done, I sit them in a saucer to drain, and then return them to their rightful home when they’re…less drippy.
General tips for watering
- Regardless of whether you’re top or bottom watering, don’t leave your plants sitting in water for too long. How long it takes varies (some take hours) so I check them periodically with a moisture metre.
- Any water that drains from the bottom after top watering should be removed (I’m on the lookout for a turkey baster to do this) – you don’t want mud at the bottom of your plant
- Similarly, if you’re bottom watering, remove either the plant from the tray or the water from the saucer once you see the top of the soil begin to glisten (or before if you’re warding off gnats)
- Plants can go into shock if you water them with water that’s either too hot or too cold. Either let your water sit out until it reaches room temperature, or add a tiny bit of warm water if you’re impatient.
- Some people claim that plants like cool water in summer. I have no idea if that’s true.
- If you have access to rainwater, use that. If you have a garden but no water-catching system, leave a few receptacles outside and hope for the best.
And that concludes everything I know about bottom and top watering.
As I said, there are pros and cons to both, but the important thing is that you remember to water your plants at all (but not too much).