Watering indoor plants: tips & tricks for houseplant irrigation

Katja
Katja
Katja
Katja

I study landscape ecology and through my studies have discovered a love for plants. Plants are not only beautiful, but also have countless fascinating survival strategies. To bring a bit of nature into my home as well, I nurture my houseplants and herbs on every possible windowsill.

Favourite fruit: rhubarb and all kinds of berries
Favourite vegetables: onions and garlic

Watering indoor plants can be a tricky business, but if you follow a few basic rules, your houseplants will surely thank you.

Watering an assortment of houseplants
Regular watering is essential for the survival of houseplants [Photo: KucherAV/ Shutterstock.com]

Not all houseplants have the same water requirements, so you cannot lump them all together. Here are some useful tips on watering indoor plants correctly.

When and how often should you water houseplants?

There is no one-size-fits-all solution for determining how and when to water indoor plants. Houseplants have different requirements that also vary depending on the plant container, soil, season, humidity, plant size and temperature.

As a rule, regularly watering in small amounts is better for the plants than infrequent but excessive watering. Signs of a clear lack of water are when the soil loosens from the rim of the pot, (i.e. collapses towards the centre) or when the plant’s leaves curl or hang down limply. In contrast, brown spots or discolouration on the leaves in combination with a musty smell indicate overwatering.

Person watering potted plants indoors
The water requirements for plants depend on many factors [Photo: Taras Garkusha/ Shutterstock.com]

Watering houseplants in summer and winter: In general, houseplants need to be watered more often in summer than in winter. Not only are many houseplants in their growth phase during summer, but there is also more light and heat available which speeds up water evaporation. As for what time of day to water indoor plants, the consistent environmental conditions in most homes make it fine to water plants at any time of day.

Water houseplants as needed

Of course, the plant’s water requirement is the main factor that determines how much watering it needs. The following categories serves as a guideline for how much water different types of plants need:

  • Plants with low water requirements: cacti and succulents (i.e. plants with thick and fleshy leaves), citrus plants, some herbs and plants from tropical, subtropical and arid regions usually have a low water requirement. For such plants, the soil does not always have to be evenly moist. It is even recommended to let the substrate dry out a little between watering to keep the plants healthy.
Watering an assortment of succulents
Succulents and cacti fare well with little water [Photo: dinodentist/ Shutterstock.com]
  • Plants with moderate water requirements: such as pothos (Epipremnum) and Syngonium, i.e. plants with many large, thin leaves. They are often found in the tropics and subtropics, where they usually grow in the shade of larger plants. Water these plants regularly but do not let them stay permanently wet or even damp. Only keep the root ball evenly moist. Other plants with moderate water requirements include the Monstera adansonii, the weeping fig (Ficus benjamini) and the autograph tree (Clusia).
Watering houseplants with large leaves
Plants with large, thin leaves need regular watering [Photo: New Africa/ Shutterstock.com]
  • Plants with high water requirements: carnivorous plants and swamp plants such as the Venus flytrap (Dionaea muscipula) and the papyrus (Cyperus papyrus) respectively, are native to very humid or wet regions. They need to be watered frequently or even stand in water. Giant taros (Alocasia macrorrhyzos), calatheas (Calathea), Chinese evergreens (Aglaonema), Alocasia, peace lilies (Spathiphyllum) and avocado (Persea americana) also have high water requirements.
Venus flytrap in a pot
Carnivorous plants have a high-water requirement but do not tolerate lime [Photo: Studio Barcelona/ Shutterstock.com]

The most common way to test the soil is with the finger test, i.e. putting a finger into the top few centimetres to check for dryness. For moisture-loving plants with high water requirements, never let the substrate dry out and always keep it moist. If the soil surface feels dry, water immediately. Let the top 2 cm of soil for plants with moderate water requirements dry out a bit between watering. For some plants with a low water requirement, the root ball may dry out completely.

Tip: Plants with a high water requirement benefit from a layer of mulch on top of the soil. The mulch curtails water evaporation from the substrate.

What to do if you overwatered your houseplant

Overwatering a houseplant is one of the most common mistakes. Whether trying to help a sickly-looking plant or encourage it to grow faster, watering a plant too much over a period of time can quickly lead to waterlogging and root rot. If the soil is moist and smells musty, the plant likely has root rot. In this case, stop watering (at least for the time being) and double check the plant’s water requirement. It is also a good idea to replace the soil and put a drainage layer at the bottom of the pot so that the water drains off better in future.

Transplanting to a prepared pot
To avoid waterlogging, add a drainage layer to the bottom of the pots [Photo: Bogdan Sonjachnyj/ Shutterstock.com]

Expert tip: Some plants should not be watered at certain times, namely during dormancy. Citrus plants, for example, require a resting phase to induce flowering. The Christmas cactus (Schlumbergera x buckleyi), desert rose (Adenium) and amaryllis lily (Hippeastrum) also have dormancy phases during which you should not water them or only water sparingly.

What kind of water is suitable for indoor plants?

Most houseplants prefer water that is low in lime. Rainwater is particularly suitable and can be collected in a water butt. Another option is to mix tap water with distilled water, which you can get at a hardware store. This is desalinated water that dilutes the lime in the tap water. You can adjust the amount of distilled water in the mixture based on the water hardness, which you can measure with test sticks. Boiling or letting tap water stand can also help.

The right mixing ratio is determined not only by the tap water, but also by the specific plant. Carnivorous plants, for example, only tolerate very low levels of calcium in their water.

Tip: If you water with calcareous water for a long time, you may see white deposits on the leaves and soil. In this case, consider diluting or descaling the water you use for watering.

Methods for lowering lime levels:

  • Boil or let stand
  • Mix tap water with distilled water
  • Use rainwater as it is naturally softer
Monstera being spritzed with water
Some houseplants like to be sprayed with water to simulate higher humidity [Photo: Alexander Knyazhinsky/ Shutterstock.com]

Since distilled water does not contain any minerals, it should not be used exclusively for watering. Plant roots need some minerals, namely salts, to be able to absorb the liquid. If there is a lack of such minerals, you should add fertiliser. Adding fertiliser is an important care measure for almost all houseplants during their growing seasons. Our Plantura Liquid Houseplant Food is ideal for many indoor plants. It not only strengthens the leaves and shoots, but also ensures strong root growth thanks to the microorganisms in it. Depending on the needs of the plant, add fertiliser to the water more or less frequently during the growing season − always check the label for the appropriate dosage.

Liquid Houseplant Food, 800ml
Liquid Houseplant Food, 800ml
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  • Perfect for a wide variety of houseplants & foliage plants
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Tip: The concentration of calcium and magnesium compounds, as well as other metals, determines the hardness of water. When combined with other minerals in the water, water-insoluble calcium and magnesium carbonates can form. After watering, these are dissolved by soil acids, during which these acids are depleted. This results in the acid concentration in the substrate to decrease and become more alkaline. Most plants, however, require slightly acidic or neutral soil. For this reason, it is important to water potted plants with soft, low-carbonate water.

Summary:

  • Almost all indoor plants need a slightly acidic substrate.
  • Some plants need particularly soft (low calcium) water. These include bog plants, for example the pitcher plant (Nepenthes) and the sundew (Drosera), and plants from rainforests, such as orchids (Orchidaceae).
  • Cacti and succulents, on the other hand, prefer calcareous substrate and hard water. These include popular houseplants such as the snake plant (Sansevieria) and the cyclamen (Cyclamen persicum).
  • Some houseplants such as Tradescantia zebrina, angel’s trumpets (Brugmansia), spider plants (Chlorophytum comosum) and pothos are tolerant of lime-rich water as long as they are planted in suitable, slightly acidic soil.
A snake plant being watered
The snake plant can be watered with tap water without any problems [Photo: New Africa/ Shutterstock.com]

How do you water houseplants properly?

The answer to this question depends on the type of indoor plant. In most cases, plants should not be watered from above onto the leaves because the water does not always reach the substrate and evaporates directly from the greenery. But even here there are exceptions. For example, water is poured directly into the bromeliad’s funnel-shaped leaves. Additionally, many houseplants, especially those from the tropics, prefer high humidity, which you can achieve by misting the leaves with water. This, however, is a separate care measure from watering.

After watering your indoor plants, wait about fifteen minutes before removing the excess water from the bottom of the pot or saucer. As a rule, most plants do not tolerate waterlogging.

Top and bottom watering houseplants
Most houseplants should be watered from below [Photo: OLESYA BOLTENKOVA/ Shutterstock.com]

Alternatively, you can also water houseplants from the bottom. This means that you pour the water into the saucer, wait about 15 to 20 minutes, and then pour out any remaining liquid. This way, the plant and substrate absorb the water out of the saucer as needed. This watering method is particularly suitable for plants with sensitive and dense foliage, such as baby’s tears (Soleirolia soleirolii). Since nutrient salts are not flushed down by the water with this method, white deposits can form on the surface of the substrate.

Another option, which is suitable for particularly dry substrates, is to submerge the plants. Place the plant in its pot in a bucket of water and wait until no more bubbles appear. Then, lift the houseplant out of the water and allow some time for excess water to drip off before returning it to its spot.

Bottle watering a potted plant
Automatic watering systems can be helpful if you travel a lot [Photo: Khoe/ Shutterstock.com]

Automatic watering systems for indoor plants

Whether away for the holidays or just a busy life, automatic watering for indoor plants is useful. There are various methods available for this:

  • Bottle watering: The lid of a water bottle is pierced with small holes and the bottle is placed into the soil upside down. This allows the water to gradually flow into the substrate.
  • Thread watering: A bucket of water is placed next to the plants to be watered. Long pieces of cloth or thread are weighted down into the bucket on one side while the other side is put into the soil. The cloth or thread transports the water from the bucket to the plants.
  • Bathtub watering: You can also put wet towels in the bathtub and place the plants on top, without a planter. The plants absorb water from the wet towels.

Such systems may be problematic because they cannot take the plants’ individual water requirements into account. Mainly, they are not suitable for plants with low water requirements. Discover more watering methods and helpful tips in our article on watering plants while on holiday.

In addition to regular watering, indoor plants also need feeding regularly. Here is what you need to bear in mind when fertilising houseplants.

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