How to Flush Houseplants Without Overwatering

This post may contain affiliate links. Read the full disclosure here.

Flushing house plants is one of those things that most people either do religiously or have literally never heard of.

I’m an outlier here, purely because house plants are my passion but also I neglect them (hilariously/sadly, I spend hours watching other people care for theirs on YouTube). So I know about flushing, do it sometimes, but largely just think ‘hmm I really should flush my house plants’ and then don’t.

I think of it as being a bit like taking a multivitamin or drinking filtered water – it will make a big difference for some people, but the vast majority of us don’t need to do it. It would probably benefit us a bit to flush our plants/drink filtered water, but won’t improve our lives significantly.

With plant care, I believe the secret to a lot of people’s success is spending time with them. If you’re playing music to your plants, talking to them, or flushing them, you’re also noticing any changes in their appearance.

It’s not what you’re doing to them – it’s the fact you’re spending time near them at all.

That being said, there are plenty of reasons to suggest that flushing your plants is worth your time.

Why flush your house plants?

Flush if you’re using hydroponic nutrients

It doesn’t matter if you’re using them with leca or soil, you should still flush periodically. Hydroponic nutrients have a lot more macro and micronutrients because they’re sold as complete foods designed to be used in soilless systems.

If you’re familiar with leca, then you’ll know that a white crust of old nutrients forms pretty quickly, and you need to flush it through.

If, like me, you’re an old hat with leca, and you’ve noticed that flushing doesn’t always shift the white crust, you may come to the conclusion that if it doesn’t dissolve in water it’s probs pretty inert and won’t hurt your plants. I have no idea if this is true but the cold facts remain that:

  1. My plants are unmoved by the white crust ( so far)
  2. This way, I don’t need to flush

Should I? Probably.

Flushing plants removes salts from tap water

Again, this is true but also not as big of a deal as you might think. It takes ages for salts to build up in soil enough to damage your plant – so long that you’ll probably have repotted it and changed the soil so you’re back to zero anyway.

However, if you’re someone that pretty much exclusively bottom waters your plants, you might want to consider flushing every now and again. I would do it prior to every time to fertilise or if you add nutrients when you bottom water, every 6 or so weeks.

Flushing can improve the flavour/yield of crops

See, this is where flushing is important. For most of us, it’s not ever going to make THAT much of a difference. However, when it comes to growing crops, flushing can help control nutrient uptake and improve flavour and yield.

It varies a lot between different plants, but I’ve heard that chilli growers use flushing to adjust the heat of their fruit. Flushing the soil and then adding nutrients a few days later can improve the plant’s absorption. Many growers also flush the soil before harvest because it makes the flavour less harsh.

By the way, a lot of the information about flushing comes from people growing weed. And whether you agree with it or not, you have to concede that these people know their shit.

Flushing mimics rain

All research points to the fact that plants don’t like to be rained on (who does??!!), because it interferes with photosynthesis. Yet this is cited to be a reason to flush. I don’t know enough about what plants like to say whether this is right or wrong BUT it’s not a strong enough argument for me to start religiously flushing my house plants.

Flushing can stop nutrient lockout

Nutrient lockout occurs when the nutrients in hydroponic fertilisers impede one another’s performance.

I use General Hydroponics Flora series, which tells you that you need to add each of the solutions to water individually, rather than mixing the three together and adding that concoction. This is to avoid nutrient lock out.

Nutrient lock out can also occur when too many nutrients have built up in the soil/water. Flushing is the easiest way to get a fresh start.

Flushing is also a way to combat over fertilising if you’ve accidentally either fertilised too frequently, or you’ve messed up the dosage.

Do you need to flush house plants?

I think you should flush your house plants if:

  • You exclusively bottom water
  • You use hydroponic nutrients
  • You have hard tap water

Other than that, I don’t think it’s necessary.

The article is coming across as if I don’t agree with flushing plants, and that’s not true – I think it can definitely have its benefits. I just don’t think it’s necessary for the majority of us.

How to flush your house plants

There are various technical demonstrations of this, but it doesn’t need to be any more complicated than thoroughly watering your plant and allowing the water to flow out of the drainage holes. A thorough flushing shouldn’t take any more than five waterings.

I think it’s important to dry your plants after flushing – especially if you use a dense substrate. If you live somewhere warm and bright then you probs don’t need to worry, but here in the UK, if you’re flushing a cactus you might want to consider drying out the soil after flushing.

In fact, professional cactus growers water their plants deeply and often, but make sure to completely dry the soil out afterwards.

How to dry your house plants after flushing

Sun

Sun hot. Dry soil.

Just be sure to protect your plant from direct sunlight if it’s not used to it. I use the VERY technical technique of lying my plant down so the leaves are in the shade and the pot is in the sun.

Hairdryer

Use a low setting (both heat and speed) otherwise, you risk both burning your plant and blowing soil everywhere.

Grow lights

These are ideal because they generate a nice amount of heat – enough to dry the soil but not enough to burn the plant. I like the MarsHydro ones.

How to avoid root rot after flushing

This is something that can confuse new plant people, but overwatering and the subsequent root rot are NOT caused by the plant being watered by a lot of water at once. For one thing, most of the water will drain away.

If you have root rot that you think is caused by flushing, make sure you’re considering everything on this list:

Drainage holes

I have a whole article dedicated to convincing you that you need drainage holes in the bottom of all of your plant pots. Of course you don’t NEED them, but it makes life much easier.

When you flush your plants, make sure that all the excess water has drained away. You don’t want the plant sitting in water. As soon as it’s watered, it needs to start drying out.

Whether you leave it alone or help it along, it needs to start drying out, otherwise, you end up with an oxygen-less quagmire, and you’ll risk root rot.

If you don’t have drainage holes, don’t flush. You’ll end up with mud.

Appropriate pot size

If the pot is too big, you’ll have too high of a soil:root ratio. the soil will hold more water than the plant can use, it’ll stay too wet for too long, and you’ll end up with root rot.

Appropriate substrate

Certain plants are better suited to certain substrates BUT if you’re an underwaterer that tends to use a denser soil mix to make up for your general neglect, you may want to rethink flushing. A dense soil will end up too wet, and again, it’ll be a muddy bacteria nursery.

Frequency of watering

You can flush away to your heart’s content if you have your watering frequency correct. Again, it’s not the volume of water that causes overwatering, it’s the lack of oxygen that results from soil staying wet for too long.

If you’re still unsure about when you should be watering, don’t bother with flushing. Instead, take the time to really get to know your plants, and learn when to water them. When you’re more confident about what you’re doing you can add in flushing if you like.

Light/humidity/warmth

The trinity that you need to balance to get your plants to thrive. If your environment is too dark or cold, the soil may be staying wet for too long, in which case you need to either not flush, increase the temperature or move the plant to a brighter spot.

If you have high humidity, you may need to keep an eye on the roots after flushing, because it can take longer for the soil to dry out, and it might be a good idea to sit it under some grow lights.

Final thoughts

If you’re far enough into your plant care journey (my, what a wanky sentence) to be considering flushing, then you’re probably familiar with the causes of root rot and also why flushing when necessary shouldn’t increase the risk of root rot much (if at all).

For those of you that are worried about root rot, don’t worry about flushing. Not flushing your plants is very unlikely to cause them any damage. Forget about it for now, and you can add it in when you’re more confident about root health.

Flushing leca plants is more important, but if anything, it reduces the risk of root rot, because it forces oxygen past the roots.

Caroline Cocker

Caroline is the founder and writer (and plant keeper) of Planet Houseplant

Leave a comment