How Often and When to Water Your Indoor Cactus

Your indoor cactus will thrive if you follow these best watering practices

Cacti have become a popular houseplant and caring for them will ensure a long life. It’s a common misconception that cacti don’t need much watering. All cacti need water, especially during their growing period. Water is important for photosynthesis and transpiration. Factors such as ambient humidity, temperature, sunlight, type of soil and even type of container may all affect how much water is needed. This guide will explain how often to water cactus, how to water a cactus and when to water a cactus.

In a previous article, The Complete Cactus Care Guide, we explained that Cacti can be desert-dwelling plants that thrive in dry and hot conditions (desert cacti) or forest-dwelling plants that grow best in shaded areas (forest cacti or jungle cacti).  This article talks about watering for desert cacti. Desert cacti varieties include:

• Cereus
• Cleistocactus
• Echinopsis
• Mammillaria
• Opuntia

Given their natural desert environment, cacti will grow best in lots of light, good drainage, high temperatures and low moisture. For your cactus to grow strong, it’s best to recreate their natural habitat. Here are key things to think about when watering your indoor desert cactus.

What type of water should be used to water an indoor cactus?

Most people don’t really consider what type of water to use for cacti and simply go for the tap. The ideal water for a cactus is rainwater or distilled water. Rainwater contains healthy minerals that feed a cactus. Distilled or filtered water has various impurities removed, making it safer for drinking and for watering your cactus! Try to avoid using tap water as the minerals really do accumulate in the soil and your cactus might be sensitive to them.

Cacti have a hard time absorbing water that is too cold for them so warm water is best. The right water temperature is between 30 and 40 degrees Celsius. The water will quickly cool down when in makes contact with the soil.

When to water a cactus

Cacti do most of their growing in the warmer seasons. Therefore, during the spring and summer, they need a deep soak to give them the supplemental moisture needed to support their growth. Water your cactus only when the soil is completely dry. During the warmer seasons, this could be every 10 to 14 days.

Cacti will go dormant starting in the fall and until the end of winter. During their dormancy period, they need less watering, when the soil is completely dry. This could be every 4 to 6 weeks.

Generally, you should water a cactus in the morning. This way, the warmth of the day will help the soil dry, leaving no excess moisture by night time. If moisture stays too long it can promote unwanted bacteria to form.

How to know if the soil is dry

Before watering your cactus, it’s important to monitor its condition and ensure that the soil is completely or almost completely dry. You can use a moisture meter (hygrometer) or just your fingers to determine whether or not the soil is completely dry.

How often should you water a cactus?

In order to promote optimal growth of an indoor cactus, it’s important to water it as soon as the soil has dried out completely. In the spring and summer, this could be about every 10 – 14 days.

In the winter, potting soil may take a bit more time to dry out completely. Since the cactus could be in dormancy during this period, water about every 4 to 6 weeks.

How to water a cactus

When it’s time to water, it’s best to water deeply. Soak the soil thoroughly until water drains from the pot’s drainage holes. If there are no drainage holes, then your cactus is in the wrong pot! It’s important to plant cacti in pots with drainage holes in order to allow water to drain from the soil rapidly.

You can also water your cactus from the bottom. To do this, place the pot with drainage holes in a saucer or other container filled with water. The soil will absorb water from the bottom and thoroughly hydrate the roots. You can leave it for about 30 minutes or when the soil is fully soaked. You’ll be able to see the moist soil from the top.

Regardless of the method you use, do not mist your cactus! Water on cactus pads can promote disease formation, brittle roots and mouldy pads.

Signs of an underwatered cactus

Overwatering is the most common cause of health problems for cacti but sometimes underwatering can happen too. Either one can spell trouble for your cactus. Keep a close eye on your cactus for signs of poor watering practices. Look out for these symptoms of underwatering:

• The cactus is discoloring, turning light green or yellowish
• Its spines are turning brown or falling off
• The cactus is wilting
• Pads are withering or drooping
• The base of the cactus is decaying and turning brown

If you spot any of the above signs, simply water it thoroughly and wait for it to bounce back.

Signs of an overwatered cactus

Excess water can be more detrimental to your plant’s health than underwatering since its effects are often irreversible. Here are signs that you may have overwatered your cactus:

• The skin of some of the cactus pads are starting to split
• Pads seem to have wrinkles or folds
• The soil remains moist for too long
• The pads and base of cactus are turning brown or black
• Plants appear overly plump

Overwatering results in waterlogging in the soil. This is bad for the cactus and can quickly lead to root rot. If your cactus is turning brown and you’re wondering why, you can refer to one of our previous articles, Why is My Cactus Turning Brown?

What to do about cactus root rot

If you notice that your cactus roots are rotting, it’ll be hard to save but there are some things you can do. You can try to repot the plant, removing diseased soil, treating the cactus with fungicides and replacing the old soil with fresh soil. Wash the roots off well before repotting. A soft, mushy cactus can also be saved by cutting off a healthy piece of stem and propagating the cutting.

Conclusions about watering cacti

There is a common misconception that cacti don’t need watering but watering is, in fact, an essential part of your cactus' well-being. Overwatering will stunt growth, but under-watering will cause shrivelling. Keep an eye on your cactus for signs of underwatering like shriveled pads or overwatering like browning or overly plump pads.

Water your cactus only when the potting soil is at least 90% dry. This means about every 10 days in the summertime and spring, when temperatures are warmer and about every 4 weeks in winter, when temps are cooler and air is dryer.  The best watering method is to saturate the cactus soil completely with rainwater or distilled water and stop when water starts to disperse from the drainage hole in the potting vessel.

Proper watering is crucial in growing cacti as it helps promote growth and flowering. Although watering is a simple process, you need to make extra efforts to know when and how to hydrate your cactus houseplants. Familiarizing yourself with the factors affecting a plant’s watering needs will help you grow beautiful and healthy cactus plants in your home.

FAQs

How do you water a cactus indoors?

The best watering method is to saturate the cactus soil completely with rainwater or distilled water and stop when water starts to disperse from the drainage hole in the potting vessel.

How often do you water a cactus?

Every 10-14 days in the spring and summer and every 4 – 6 weeks in the fall and winter.

How do you know when a cactus needs water?

Only water a cactus when the soil is completely or nearly completely dry. Use your finger or a hygrometer to check for soil moisture.

Should I mist a cactus?

No! Don’t mist your cactus.

What kind of water should I use for a cactus?

The ideal water for a cactus is rainwater or distilled water.

What’s the best potting medium for cacti?

Use well-draining cactus and succulent soil.

How to drain potting media?

Use pots with draining holes.

How long should I water my cactus?

When it’s time to water, drench the soil completely, until water flows through the pot’s drainage holes.