How much water does a plant need a day? Here’s what you need to know

When it comes to how often to water plants indoors, many people default to a set schedule. Same time, same day, every week. While this is good in theory and gives you a bit of structure, it doesn’t actually provide the best care for your plants. Like people, every plant is unique and has its own set of needs. So, let’s go over how you can set up a watering schedule while still meeting the needs of each leafy (or spikey!) friend.

Metal watering can next to greenery

How often should you water indoor plants?

How often you water indoor plants depends on the type of plant you’re working with, the container size, the lighting, the humidity, the temperature, and other indoor environmental factors. You’ll find that plants in brighter lighting will have their soil dry faster than plants in lower lighting, which is why having pots with good drainage is equally as important as proper watering. The excess water will need somewhere to go.

The size of a plant also matters a lot when it comes to how much water you give your plants and how often you water them. Larger plants with bigger root systems will require more than a small plant, which is also why it’s important to make sure the pot you choose is appropriate for the size of the plant. If you put a small plant in too large a pot there’s a risk that the soil will be too waterlogged and the plant could drown or experience root rot. And vice versa! Large plants need to be in a pot that’s big enough for them, otherwise they won’t get enough water no matter how hard you try.

Different species of plants also prefer different watering methods. Succulents and cacti like what’s called the soak and dry method where you wait until the top inch or so of soil is dry, then soak it with water until it starts to drip out the bottom. Then repeat. Other plants, like ones that are native to tropical locations, prefer a higher humidity and slightly moist soil, which can be accomplished by daily misting. The bottom line is each plant has different needs, so you’ll want to know how a plant likes to be watered in order to figure out how it will fit into your schedule.

Marc van Iersel, a professor at the University of Georgia, and Jongyun Kim, ,a PhD student, published findings in Greenhouse Management magazine from the study they completed involving petunias in four-inch pots. They were trying to answer the question: How much water does a plant need a day in a day?

“For a three week period, these plants received about 16 ounces of water per plant. This is a little more than 1 tablespoon per day. Water use was not constant during the study; small plants used 1 tablespoon per day, while large plants used slightly less than 2 tablespoons per day. Overall, there was a good correlation between plant growth and the amount of water applied. The study indicated that controlling irrigation can be an effective method of controlling growth.”

One tablespoon of water is roughly 14.7mL; two tablespoons is about 29.5mL. Keep in mind that these were small plants growing in four-inch pots. How much water a plant needs in mL will depend largely on the variables we discussed above.

Person watering a snake plant
Severin Candrian/Unsplash

Setting up a water schedule

Unfortunately, it isn’t as simple as picking a day and watering all your plants once a week. No two plants are the same. That’s why when setting up a watering schedule, it’s important to take each plant’s needs into account.

The best schedule for your plant care is one where you check on all of them every  day or two. Depending on the type of plant, there could be different indicators for whether they need to be watered. A good rule of thumb is to water when the top inch or two of soil is dry; however, some plants (such as ones native to a more humid/tropical environment) like to have their soil moist.

If you notice that some of the ends of your plants’ leaves turn brown — or, in the case of succulents, start to wrinkle/shrivel up — then it means you’ll need to water them more often. Wilting and yellow leaves can also be an indicator of not enough water, but they’re equally as indicative of too much water. That’s where checking the soil daily comes in. Often the best way to know whether your plants need water will be the dryness of the soil.

If you’d like more structure than that, you can always try a spreadsheet. Set up the names of plants across the top and number the rows on the side from one to 31. Put an X on the day of the month that you water each plant and see if there’s a coordinating pattern. That will help you get a feel for which plants need to be watered when; however, there will still be situations where you’ll need to forgo your schedule.

Don’t be afraid to deviate

Even the spreadsheet won’t be perfect. When your plants need water depends largely on environmental factors, so don’t be worried if you have to water on a day you haven’t marked down. Plants will need more water during their growing season than they will in their off season. Similarly, you may have a string of days that makes your home more humid or extra dry, and you’ll notice that even that small shift can affect when you water your leafy friends.

It will basically be a trial-and-error effort. It may take a bit to settle into the schedule or get used to checking on your plants every few days. But we promise, they’ll love you even more for paying attention to their individual watering needs.

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