Water is essential for all plants. If they don't have water, they'll die, but on the other hand, if they are constantly soaked in water, they'll also die. One of the most common causes of death for houseplants is root rot, which occurs when the roots are sitting in water.
Plant with root rot
There is no set rule for how often to water your plants. Even if you and your friend have the same plant, that plant’s watering needs may vary.
This is because there are an infinite number of factors in your home that come into play when it comes to when you should water your plants, such as light, humidity, plant size, plant age, pot type, and more.
It's best to not use a set schedule to water your plants. One of the most common suggestions you’ll hear is “you should be watering this type of plant x times per week." While this sounds easy and straightforward, it’s not a good idea to water on a set schedule. The bottom line is that different plants + different conditions = different watering needs. Following a hard and fast watering schedule usually leads to chronic over or under watering.
Instead of having a watering schedule, set up a schedule for checking in on your plants to see if they’re telling you they’re ready to be watered.
The best thing for your plants is to wait to water until the soil has dried out. This could mean once a week for one plant and once a month for another. You'll know when it’s time to water by checking the soil. The most reliable method is sticking your finger an inch or two into the soil, about to your second knuckle. You can also use a soil probe or moisture meter. A soil probe is a stick that is stuck down into the soil and wet soil will stick to it. This is similar to testing brownies with a toothpick. A moisture meter gives a wet or dry reading when stuck in the soil, but this isn't always accurate.
Soil probe
Moisture meter
If you are using your finger, you can tell if the plant is ready to be watered or not based on the soil. If the soil is moist and cool to the touch, leave the plant be. If the soil is dusty and feels room temp, it’s time to water.
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Finger test
Plants like their soil to dry out to different levels. A general rule of thumb is to let the potting mix dry out ¼ to ½ way down the planter. Some plants can vary on this. For example, cacti and succulents like their potting mix dry out completely between watering. In general, plants with thicker leaves are particularly good at storing water, so they typically don’t have to be watered as often. On the other hand, ferns and calatheas like their soil to remain moist but not soggy.
To help you know when a plant needs water, watch the plant for signs of underwatering stress, such as limp, dry, and droopy leaves.
Underwatered plant
The right way to water every single plant, even cacti and succulents, is to water it deeply and fully saturate the soil every time. Water should be freely flowing out of the drainage hole. Having drainage is so important. (For more on drainage, see the Potting tab to the left.) It's best to water all the way around the pot instead of consistently in one location. This ensures that the entire rootball receives water. A rootball is another name for the mass of roots.
Watering a plant with drainage
In terms of watering location, you can either bring your plants to water, or water to your plants. For example, if the plant is moveable, you can bring it to the sink. Water until there is a stream of water coming out of the drainage hole and let it sit in the sink to fully drain. You can also water in the shower, tub, or even outside if it’s nice out. In general this makes for less mess. For plants that aren't moveable, you can bring a watering can to your plant and water until you see water filling the saucer beneath the planter. At this point, you'll want to remove the excess water in the saucer. You can use an old towel to soak up water or even a turkey baster to suck water out. Overall, you never want to leave water sitting in the saucer.
Watering plant in sink
Below are wrong ways to water:
Bottom watering is another method to water your plant. Place your plant, pot and all, in a container that holds water, like a large bowl or even the sink. As the plant sits in the water, the soil absorbs it up from the bottom. This is a great way to passively water your houseplants and make sure the soil is completely saturated. The downside to this method is it can take a while. Each plant will usually take about 20-60 minutes. You'll know it's fully watered when the top of the soil is moist. Bottom watering is great for plants that are picky about water on their leaves. For example, water leaves marks on African violet leaves. Additionally, it's important to occasionally top water plants you typically bottom water to flush salt out of the plant and prevent buildup.
Bottom watering
Overwatering has nothing to do with the amount of water you use. Instead, overwatering is watering too frequently before the soil has dried out enough. This is also why drainage is so important. Without drainage, it’s anyone’s guess as to how much water you’ll need with fully saturate the soil without leaving standing water at the bottom. Standing water is where problems lie; this causes root rot, which is when roots basically suffocate and die.
Underwatering means you're not watering frequently enough and the soil is becoming too dry, or you aren’t using enough water to fully saturate the soil and it’s never being fully hydrated.
As long as you have drainage in your planter, you can’t use too much water at one time. You could use a watering can or a 5 gallon bucket. As long as your plant has drainage, it won’t be too much because the soil will only retain what it needs and the rest will drain out.
In terms of water temperature, keep your temperatures in the moderate range. Room temperature or slightly warm is great. Steer clear of water that is too hot or too cold because these temps can shock the plant. This is because most houseplants are tropical and expect moderate temperatures.
Using tap water is just fine for most plants. There is a myth that chlorine in tap water causes issues for plants, but there typically isn’t enough chlorine in most tap water to affect plants. Distilled water isn't necessary for most plants. Plus, it’s expensive to continually water plants with store-bought water. Softened water isn't great for plants because of the added salts. Frequently watering with salty water will dehydrate your houseplant. However, if you have a reverse osmosis system that removes the salts, then you’re good to go.
Watering plant with tap water
There's also a relationship between light and water. While both are different and important factors on their own, light and water are intertwined. In general, more light means you'll need more water, while less light means you'll need less water.
In winter, plants generally don't need to be watered as often. This is because plant growth slows and plants don't require as much water. On the other hand, plants may need more water in the summer because the sun is stronger and out for longer, and the plant is pushing out new growth. This is another reason why it's important to not have a watering schedule; plants' needs change over time. Again, it’s a good idea to having a soil checking schedule, but not a watering schedule.