How Much Water For Houseplants: Test, Don’t Calculate!

Are you worried about extravagant formulas on how to calculate how much water each of your houseplants needs? Worry no more! Calculating the amount of water according to the size of the pot is not a miracle formula you need to master to water your plants the right way.

Short Sum-Up: Rather than basing watering solely on pot size, optimal houseplant care suggests tailoring watering habits to individual plant needs by assessing soil moisture before watering. This approach prioritizes plant health over rigid watering schedules.

Instead, I suggest using the ‘finger check’ and other test methods to figure out the water needs of your houseplants. It’s about testing, not calculating! Find out how and why in this post.

Why Calculating the Water Volume For Houseplants is Misleading

As a general rule, it is typically said that the water volume you give your plant should be no more than 1/4th or 1/3rd of the volume of the plant pot. Though this can be helpful, I think calculating water volumes according to pot size only distracts from the essential factor: The water needs of the plant itself.

A plant is a living being. Its need for water changes with its metabolic activity as well as with varying light, humidity, and temperature conditions. The pot size instead remains the same. See what I mean?

Instead of remembering some rule like ‘water each plant weekly’, it is better to remember the following rule of thumb:

  • The more light, the more water – The less light, the less water

Simple, but more effective for a healthy plant care routine. The plant metabolism is more active with more sunlight as this stimulates its photosynthetic activity. With an active metabolism, more water will be consumed by the plant.

Read on: Photosynthesis is the process through which a plant produces its sugars. For a balanced diet and a happy lifestyle, plants need other essentials apart from light and water. Find out what plants need to make them happy in my post linked here!

Think Different: It’s a Plant Care Routine, Not a Plant Watering Routine

A lot of plant owners think that watering their houseplants is the only responsibility we have towards our green housemates. If the plants are in a good spot and thrive happily for years, then this might well be the case.

Often though, especially with the change of seasons, with new plants or new spots, we need to take extra care of our plants. We need to check on their health and whether there are any signs of pests or diseases visible. I think it is therefore appropriate to think of our plant routine as being a care routine and not merely a watering routine.

For an easy guide on how to create a plant care routine, click through to my easy step-by-step health care check for houseplants (and then come back here to read on!).

When you start thinking of your plant practice as a care routine, it becomes easier to let go of that urge to always water plants in the exact same intervals. I have had my own experience with this – it just feels good to give your plants fresh water but often the plant itself doesn’t need any yet.

A care routine includes checking the soil moisture. By checking the soil moisture first, you will water your houseplants according to their water consumption and not according to a strict watering routine (even though we as humans would prefer the latter as creatures of habit).

Now, don’t start worrying that watering your houseplants becomes super complicated this way with varying water needs each single week. It is not complicated. Given that the plants remain in the same spot in your home for years, there will be a certain routine over time and you will get to know each of your plants’ needs better.

Quick Guide: How to Water Houseplants Appropriately

Here are a few steps to take for appropriately watering your houseplants, focusing on their water needs:

  • Check the soil moisture: Stick your finger an inch or two (2-3 cm) into the soil. If the soil is bone-dry all the way there, give it a rinse. If the soil is still moist, wait with watering. In winter, check again in your next week’s health check, in summer check after 2-3 days as hotter temperatures make the soil dry out faster.
  • Rinse your plant: Water your plant until the water starts flowing out the bottom of the pot.
  • Wait 15 min: Wait some minutes after watering until all excess water has gathered in the bottom or saucer of the pot.
  • Empty excess water: Don’t ever let your plants sit in water too long. If there is a lot of excess water, empty it!

This is only a quick guide. For more handy tips and ways to water your plants, check out my complete watering guide right here. You sure won’t be overwatering your plants again after reading this!

Tip: Is top or bottom watering better for plants? There are benefits and disadvantages, as well as some clear don’ts, for both methods. Read more in my post!

What Soil Quality Has to Do With Watering: Drainage And Moisture Retention

Another important aspect of how much water you should give your plants has to do with the quality of the soil of your houseplants. Good quality fresh soil has a twofold advantage: It has the right amount of drainage needed while at the same time it keeps enough moisture in the soil.

Drainage prevents the soil from becoming waterlogged whereas moisture keeps the roots saturated with water. To learn about why waterlogged soil is a big problem for your roots and why drainage is essential, check out my post about drainage for houseplants (and learn how to create drainage in any type of pot).

Good quality soil remains good for a couple of years and withholds the appropriate amount of moisture needed. As soon as you realize that water instantly flows through the soil and after two days the whole pot is already bone-dry, these are signs that you should repot the plant with fresh, good soil.

Tip: Do you want to DIY a good indoor soil mix? It is easy to add some drainage materials to standard store-bought soil, there’s no need to spend fortunes on specific soil mixes. Follow my tutorial post to make a good soil mix and find out what common and sustainable drainage matters you can add to your soil!

Frequently Asked Questions

Is It Better to Overwater Or Underwater A Houseplant?

Neither of them is good, as you already know. But as most plant parents tend to be too kind with the blue liquid, I would suggest keeping to the underwatering side of the balance.

Not because prolonged drought will do your houseplants better but rather because in our minds we are generally set on giving plants too much water. Hence, if we think we are underwatering our plants, it is probably an amount more suitable for the houseplants.

This doesn’t mean that neglecting your green housemates for months is ok – I’m just suggesting that whenever you water your plants, think of underwatering them. This may help to reduce the risk of overwatering, which in my opinion is way worse for plants.

A slight drought in between usually doesn’t harm your plants (some even like it). Instead, constant slight overwatering causes root rot pretty fast and weakens your plant’s overall resilience to diseases and pests.

How Do You Tell If You Are Overwatering Or Underwatering?

The symptoms of drought and waterlogging can be similar. Brown leaf tips, leggy leaves, bleached-out color, or yellowing leaves. The easiest way to find out what the cause of your plant’s ill-looking appearance is is by checking the soil moisture. If the soil is bone-hard and dry, underwatering is the problem. If the soil is moist, soggy, and of a moldy smell, overwatering has been an issue.

Whether you have been over- or underwatering your plants, it is important not to panic and water them inappropriately. A panicky counterreaction often happens when a plant has been underwatered: The plant parent wants to redeem the lack of water immediately by submerging the plant in water. The poor drought-stricken plant will be even more poorly overwhelmed by sitting in water right after going through drought.

Instead, when a plant has been underwatered, just give it a little water but check on it every couple of days. It is better to give a little now and then instead of drowning it.

As for overwatered plants, empty out all excess water from the pot and keep from watering until the top layer of the soil is dry again. Just let it recover. Then give it only as much water until it rinses out the bottom of the pot, letting the top soil always dry out before watering again.

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