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 as long as they get some.
However, some plants do prefer one method over the other. African violets, for example, don’t like getting their leaves wet at all, so bottom-up is the way to go. 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 that’s already travelled through the pot – it can cause your plant to reabsorb some salts and potentially harmful mineral deposits it’s trying to get rid of.
Top watering: pros
This is the number one reason that I top water when I do. I prefer to bottom water (more on that later), 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 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 allow this to be your primary reason for top watering. Top watering can also increase the number of pests and the likelihood you’ll attract bugs in the first place, so it’s all just swings and roundabouts really.
Diminish 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 you 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.
I’m actually considering using the tap safe stuff used for fish tanks. Surely if it can make water safe for fish it’ll be safe for fish? Anyway.
When you top water your plant thoroughly, salt an mineral are washed away. This is why it’s important that you let any excess water drain away, and you don’t let your plant stand in the water – you want it reabsorbing the nasties.
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.
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.
With bottom watering, however, any patches of compacted soil may lead to dry portions of soil. Bottom watering relies on capillary action. Top watering relies on gravity. Gravity is, if you didn’t already know, a pretty strong force.
Top watering: cons
There are two pretty big downsides when it comes to watering houseplants from the top. HOWEVER, neither of these things are 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 of your plants
A lot of plants have leaves that don’t want to get wet. In fact, very few plants enjoy having wet leaves. 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 that won’t tolerate wet leaves at all – Africa violets, for example, will rot quickly if you indiscriminately get water on their leaves. It’s hot in the parts of Africa they originate from, you see, so either there’s no rain for months at a time or the ain evaporates quickly.
Top watering plants can encourage fungus and pests
I saw a major decrease in fungus gnats when I started bottom watering almost exclusively.
Fungus, fungus gnats a lot of other pets (like spider mites) 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 soil to become 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.
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 worths 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.
I also question the quality of bathwater – I only have one bath with the only shower over it, so I’d have no way of reducing the chlorine in the water without compromising my own personal hygiene. I suppose I could try the fish de-chlorinator, but I’d worry about staining the bath.
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.
The orchid is a victim of over-watering by a friend and has only just begun growing some beautiful white roots. It’s starting growing pretty voraciously and I’m sure it’s down to being regularly soaked.
I don’t care if it never blooms because I’m a foliage girl, but my GOD it would be exciting if it did.
Bottom watering: pros
It doesn’t damage the leaves
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 extremely averse to getting their leaves wet and suffer water damage easily.
My watermelon Peperomia also hates getting wet leaves, which is weird because I propagated a leaf cutting and it actually grew seemingly healthy leaves under the water.
If you’re not sure whether your plant will mind wet leaves, then just do a bit of research and find out the kind of environment they grow in. Plants that come from arid environments are less likely to tolerate damp leaves than plants from the rainforest.
Not technically leaves, I suppose, but cacti will rot quickly if they’re regularly covered in water.
The top of the soil remains dry, discouraging pests
We’ve already talked about this. Pests like the damp. Not just fungus gnats – spider mites love them a bit of wet soil.
Encourages the roots to spread out and get stronger
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.
It’s more difficult to over water
Not impossible though!
Unless you keep your plant’s saucers constantly topped up, you’re unlikely to overwater your plants.
In fact, if you’re a serial over waterer, a small saucer and bottom waterer may dramatically improve your plant’s chances of survival.
Even if you fill up the saucer every day, you’re unlike to overwater, since the saucer can only hold a tiny amount. Unless your plant is equally tiny.
Bottom watering: cons
If you only bottom water, mineral and salt deposits can build up
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.
If 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 pain in the arse 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 gets stood in the water tray in the kitchen where he gets in everyone’s way. Luckily he doesn’t need watering very often. I’m planning on getting him a planter to go in (he’s still in his nursery pot, and seems happy enough) which I’m going to make sure is big enough to use to bottom water him.
It takes longer
Well, depending on your set up. 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.
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.
General tips for watering
- Regardless of whether you’re top or bottom watering, don’t leave your plants sitting in water for too long.
- 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 your plants to reabsorb any salts it wants to get rid of
- 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. I personally don’t let the top of the soil get wet (fookin’ gnats), but you can if you like, so long as you don’t let your plant get waterlogged
- 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. That’s what I do, and I just make sure to water my carnivorous plants and calathea first (since they’re the ones that really appreciate rainwater). I don’t bother with a water filter.
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).