How to Best Water Houseplants to Keep Them Alive

By Erin Marissa Russell

Keeping your houseplants well hydrated can be a more complicated proposition than it seems in many ways. There’s more to watering the indoor garden than simply taking a watering can to your plants every so often. As a matter of fact, caring for indoor plants can be more of a challenge than maintaining an outdoor garden, if only because most of us are accustomed to the way gardening works outdoors and must adjust our techniques to apply to houseplants.

When you’re cultivating an indoor garden, the water you provide won’t evaporate as quickly, the garden hose isn’t exactly practical, there’s no wind or breeze to help with air circulation, and the hydration needs of your plants won’t fluctuate as widely with the seasons. Even the most experienced gardeners can use some tips on how to best water their houseplants—so we’ve rounded up the best techniques and most vital information you need to hydrate the plants in your indoor garden.

Tips for Watering Houseplants and Indoor Gardens

Perform a Soil Test to Check Whether Plants Need Water

If you simply aren’t sure whether or not it’s time to water your plants, there’s a quick way to find out that doesn’t require any fancy equipment. Just stick a finger into the soil close to the root zone of the plant in question. You may be able to feel the moisture in the soil. If this is the case, don’t water your plants just yet. Another telltale sign that plants still have water accessible to them is if particles of the soil cling to your finger. This is another signal to let you know that you should wait a while longer before watering your plants.

Watch Out for Soil Shrinkage

When the soil in your plant containers begins to dry out, it will start to shrink up and pull away from the edges of the pot. This actually happens because as water moistens the soil, it expands, so as it dries, it loses this excess volume. Make it your goal to provide plants with their next dose of water before you see this happening. Even those of your plants that prefer to dry out a bit before getting their next round of water don’t need to dry out to the point of soil shrinkage.

Consider Watering Houseplants from the Bottom

One way to make sure your indoor garden gets plenty of hydration and that the moisture is applied evenly throughout the container is to water your plants from the bottom using a technique called sub-irrigation. First, place your plant pot into a dish or tray with slightly high sides that you’ve filled with water. The water will slowly seep into the soil surrounding your plant. Be careful not to add so much water to the dish you are using that your plant container is able to float, as this can cause it to tip over, endangering your plant.

Sometimes, the soil where your plant is growing may absorb all the water in the dish and still not be completely saturated. If this happens, simply add more water to the dish and allow your plant to continue soaking it up. When the plant has stopped absorbing water, remove it from the dish and sit it in a sink or in another location where the extra moisture can drip from the container’s drainage holes without making a mess. Watering your plants from the bottom this way will also flush away more of the salts that accumulate in soil that watering from the top would.

Determine How Much Hydration Plants Need

In general, the guideline on how much water to give your plants is to provide an inch of water per week. However, there are a variety of factors for gardeners to consider that can shift this standard amount, resulting in plants that need less or more than an inch of water each week. These factors are listed below. There’s no formula for how to calculate each of these metrics so you can end up with an exact amount of water to provide your plants with perfect hydration. Instead, simply be aware of the effect these issues can have on your plants’ moisture needs, and adjust accordingly, observing how your plants (and their soil) respond to the changes you make.

Are your plants in a growth period, during which they require more water?

Are your plants dormant, during which they require much less water or, in some cases, no water at all?

Do your plants have extremely large leaves or leaves that are thin? Do your plants have fine, thin roots that stay near the surface of the soil? Plants with these characteristics tend to require more water than other plants that do not fit this description.

What species is your plant? Different plant varieties have different basic needs for their hydration.

How large is your plant? When plants are larger in size or simply more mature and well established, they will require more moisture than when they were smaller.

Where is the plant located? Plants in a bright window that gets direct sunlight are bound to need more water than those in dimmer areas or spots with indirect light, as the water will evaporate more slowly.

What size of container is your plant growing in? Smaller containers have less capability to retain water for plants to use later, so plants in small containers will need to be watered more often than those in larger containers.

What is your plant’s container made of? Certain materials may soak up some of the water themselves or get hot and contribute to the process of evaporation, turning water into water vapor before plants can access it.

What type of soil is your plant growing in? Soils that are loose (many potting soils, perlite, or sand, for example) will allow much of their moisture to drain right through them. Plants growing in these looser soils will need to be watered more frequently than plants growing in heavier soils that retain water for longer.

What time of year is it, and what is the weather like? Plants need more water during warm seasons than they do in cool weather.

Pour Drained Water Out of Trays or Saucers

To catch the water that drains from the holes in plant containers, many gardeners place a tray, saucer, or shallow dish underneath their plants. This simple solution keeps the excess water from dripping onto the ground and ruining carpets, hardwood floors, tables, and other furniture. However, the surplus of water shouldn’t simply be allowed to stay in the tray.

Stagnant water can become a breeding ground for pest insects, and it’s also not good for the plant to sit in the water with the bottom portion of its soil becoming soggy. Whenever you water your plants, allow the extra moisture to drain into the tray underneath your plant. Then simply pour the water that has collected in the tray out into the bathtub, down the sink, or onto the soil outdoors.

Learn How to Apply Fertilizer to Houseplants

When it’s time to give your houseplants a dose of fertilizer, first moisten the soil by watering your garden as usual. Use a liquid fertilizer, and dilute it to half strength with water, then apply it to the already wet soil. It’s important never to apply fertilizer to dry soil, even if the fertilizer comes in liquid form, or you risk burning the roots of your plants with the fertilizer.

Master the Meaning of Watering Terms on Plant Labels

Sometimes, plants you procure from a nursery or garden center will have watering information listed on the seed packet or the plant care tag. Plants sold by online suppliers may display this information in the product descriptions on their website. However, it can be difficult to determine exactly what “heavy” watering means. Below, we’ve listed a translation of each of these terms that puts them into a form that’s easy to understand and put to use.

Heavy: Plants with heavy watering needs should be kept constantly moist but not overly saturated. You should not allow the soil of plants that require heavy watering needs to completely dry out between waterings.

Medium: Hydrate plants that have medium watering needs thoroughly but less frequently than those with heavy watering needs. You should permit the surface of the soil to dry out in between watering sessions for plants with medium watering needs.

Moderate: Plants that have moderate water needs should be treated similarly to those with medium watering needs, with one exception. Instead of allowing just the top layer of soil to dry between doses of water, when you’re caring for plants with moderate water needs, let all of the soil become dry before the next time you water.

Light: Plants with light watering needs require the least fuss and maintenance of all. Simply get the soil around the roots of these plants damp, and allow it to dry out completely before watering the plants again.

Check the Temperature Before Applying Water to Your Plants

It’s a bit obvious that you shouldn’t use warm or hot water to hydrate your plants. However, many gardeners don’t know that cold water can be a problem as well, even when the weather is hot and it seems like a cool drink would be refreshing. Always use water that is lukewarm (room temperature) to give to your plants. If necessary, you can always let warm or cool water sit out on the countertop until it’s reached a tepid state.

Find Out How to Spot Issues with Water Quality

Most gardeners use water from the municipal supply (such as tap water or water from the garden hose) to hydrate their plants. Municipal water has sometimes been treated with chemicals. Although these chemicals haven’t been added to water in large quantities, as time goes on, the small amount of chemicals in your water can build up to cause a reaction in your houseplants. If you aren’t sure whether your city’s water supply has been treated with chemicals, you can look this information up on the city website or contact the water utility department to learn more about it. Plants sometimes will begin to show a response to low water quality after one year, and after five or more years, they are especially likely to have a negative reaction to water quality problems.

The most important factors to consider when it comes to using municipal water for your indoor garden are chlorine, fluoride, and the pH level. The chlorine normally comes in the form of sodium hypochlorite, and water is treated with it to keep bacteria to a minimum. Chlorine does not cause problems for most plants, but should your plants be particularly sensitive to it, it is possible to remove chlorine from the water. Simply pour the water into a container with a wide mouth and allow it to sit out. Within a few days, the chlorine should have evaporated, leaving the water behind.

Unlike in the case of chlorine, when fluoride is added to the municipal water supply, it can cause problems for your plants—some more than others. Plants that have long, slender leaves are especially likely to have trouble when the water they’re given contains fluoride. Vulnerable plants include dracaena, Easter lily, freesia, parlor palm, prayer plant, and spider plant. You can help decrease the fluoride that can build up in potting soil by flushing it with water that does not contain fluoride, such as rainwater or bottled water. With a somewhat substantial cash investment (a few thousand dollars), you also have the option of installing a reverse osmosis system to reduce the fluoride in your tap water.

The optimal pH level for garden soil is between 5.0 and 6.0, but it’s not uncommon for municipal water supplies to have a higher pH level. This is especially problematic when you’re using the water to hydrate plants that prefer acidic conditions, like citrus trees. Plants in the outdoor garden are less likely to be affected when the pH of the water they are provided is higher than they prefer because there is so much soil to go around that the pH level of the water does not affect the soil’s pH.

When soil has a high pH level, plants are less able to access certain nutrients, including iron. Plants that are deficient in iron (otherwise known as being “chlorotic” may develop leaves that have green veins with discoloration of the tissue between the veins that turns a yellow shade.

However, houseplants have a very limited quantity of soil to draw from and so are at greater risk of negative consequences when the water used to hydrate them has a higher pH level than is best for them. Water-soluble fertilizer can help lower the pH level of soil by increasing its acidity, but make sure to dilute the fertilizer so it’s only at half strength. Another way to lower the pH of your water is simply to add a bit of acidic liquid to the water, such as the juice of citrus fruits or vinegar.

You can bypass the problem of chemicals in the municipal water supply completely if you choose to water your plants with rainwater, bottled water, or distilled water. However, some of these options cost more than using tap water, or they may require more planning ahead than simply using tap water would require. The summer may be the most convenient time to use rainwater for your plants because this is when they need the most water as well as being a season when rainfall is prevalent.

Now you know the best practices to follow when watering houseplants. Once you start implementing what you’ve learned, your indoor garden will become healthier overall. Giving plants adequate hydration (but not too much) and staying vigilant against the problems that can arise surrounding the process of watering plants is one of the best ways to ensure your plants will thrive and flourish.