How Often to Water Cactus?
Known for their drought resistance and generally low profile, cactus plants are a treat to have around. When they’re small, they’re a cute addition to your home’s or garden’s decor, when in bloom, they’re a sight to behold, and when it comes to maintenance, they really don’t ask for much.
One difficulty with cactus plants, however, is getting their watering requirements right. It’s easy to go overboard with watering this plant, so it’s important to know how often to water cactus your plant.
What follows is my take on the best approach to watering cactus plants, which considers multiple factors that may impact the watering frequency of your cactus.
How to Water Cactuses?
An approach that often leads to issues is to set up a predefined watering schedule (e.g. watering once or x times a week), which may work for some plants and will surely keep your cactus plant hydrated, but maybe overly so.
A predefined watering schedule doesn’t work for the simple reason that factors such as temperature, plant size, soil dryness, airflow or ventilation will differently impact the water requirements of different plants.
A better approach would be to take all the factors into account and essentially water the plant when it needs it.
A quick way to make the determination that a cactus plant needs watering is to check the dryness of the soil. Is the soil completely dried out? Water the plant. The upper layers of the soil are still moist? Check again in a few days.
Cactuses are excellent at storing water in their roots and stems to survive drought periods and unpredictable weather with little to no rainfall.
Some believe that just because cactuses are so well adapted to drought that they should receive very little water when watering. But that’s not the case.
When watering, you should water until water comes out through the drainage holes at the bottom of the pot. Then once the water is drained, remove the excess water from the saucer.
If you’re growing cactuses indoors, you can of course manipulate weather conditions, but that doesn’t mean your cactus will also adapt to different conditions. Therefore, you must make sure to create conditions similar to those from where the plant originates.
The following factors will all have a say in how often to water cactus plants, so pay attention to all these things to best meet the watering needs of your cacti:
Cactus plants require a few hours of direct sunlight per day, which will inevitably increase evaporation, leading to the soil drying out faster. Watering frequency will change depending on whether the plant is in a north- or south-facing window.
It’s important to note that cacti require evenly distributed light, so periodically rotating the plant is essential to allow the plant to get light evenly.
Temperature & Humidity
Higher temperatures coupled with low humidity will also increase evaporation, which can mean more frequent watering compared to high humidity environments or low temperature environments.
Seasonal temperature changes and cactus active growth periods will also have a say in how often or how infrequently you will need to water your cactuses. During active growth periods, cactus plants will need to be watered more often compared to dormant states.
Increased ventilation will also increase evaporation, which in turn means more frequent watering. This is usually the case when you move your plants from indoors to outdoors, where there is better aeration and therefore increased evaporation.
You can pick a good quality commercial cactus mix or create your own mix using coarse sand, perlite and potting soil for increased drainage.
A soil that drains fast and dries fast may require more frequent watering, but it will also make sure the plant’s roots are not sitting in water for too long and fungal diseases are staved off.
Type & Size of Pot
Terracotta pots and clay pots are the gold standard for cactus plants because of their porous structure that allows water to evaporate more quickly from the soil. Plastic pots don’t allow water to escape at the sides of the pot and create a moist environment favorable for fungal diseases.
A large pot will require more water, but it will also take longer for that water to evaporate, so generally speaking, it’s not a good idea to oversize the pot of a cactus plant. Make sure the pot is size-appropriate and when repotting, go for one size up only.
Type & Size of Plant
A small cactus that is still developing may need to be watered more often, while an already established cactus may go much longer without water.
Cactus plants native to tropical regions will have different watering requirements compared to those native to deserts. Those cactuses that live in arid conditions will go much longer without water, while tropical cactuses will require more frequent watering.
When you pick out your cactus, check to see if it’s native to tropical climates or native to deserts to have an idea about its general watering requirement.
Are You Overwatering Your Cactus?
It’s much more likely that you’re overwatering your cactus than underwatering, which is a lesser problem compared to watering in excess.
While it should be fairly obvious that your cactus is getting too much water, here are the symptoms of an overwatered cactus:
- Squishy, mushy stem
- Changes in color — base of cactus turns brown or black
- Rotting and decay is noticeable
Once the root system of your cactus plant is damaged by root rot, it can no longer absorb water and nutrients, and it will die.
It may not be immediately apparent that your plant is overwatered since by the time external symptoms appear, the root rot is well underway.
When you suspect root rot, you should check the roots to assess the damage — look for any signs of healthy roots, they should be white and firm to the touch; brown or black or mushy roots are diseased and should be removed.
You can try to salvage the plant by repotting in dry potting mix and holding off watering for a week to see how the plant fares.
Once the damage of the roots is too significant, root rot disease becomes irreversible. Unfortunately, for most root rot diseases the outcome is grim and therefore, prevention is the best medicine for this ailment that has probably caused the downfall of many indoor cacti plants.
Are You Underwatering Your Cactus?
It’s hard to imagine that you can underwater cactus plants seeing how they can go without water for as long as 4 weeks. But even so, underwatering should also be considered as a potential issue when it comes to watering.
So, even though it’s rare, the symptoms of an underwatered cactus plant include:
- Cactus is looking shriveled and puckered
- Cactus changes color to dark brown
- Plant becomes calloused
Once the water reserves in the plant become used up, you can expect these symptoms of drying out to appear.
No need to panic, however, as thorough watering can remedy these issues. Give the pot a good soak-through and you’ll notice the cactus bouncing back to normal health. Luckily, underwatering is much more harmless than overwatering.
Watering Indoor Cactuses vs Watering Outdoor Cactuses
You may keep your cacti outside during the summer and you may have cactus plants that can be planted outside.
For indoor cactuses, observing the watering recommendations above will give you a good sense on how much and how often you should be watering your cactus plants.
Bear in mind that there are differences between the watering needs of small cactuses that are still growing vs large cactuses that are already established, and desert cactuses vs tropical ones.
For cactus plants kept outside, usually rainfall is enough and no additional watering may be needed, unless there’s heavy drought, low humidity or prolonged sun exposure during the day.
Keeping an eye on temperature fluctuations, sunlight, humidity, soil dryness and the general health of your plant will become second nature to you after a while, and you will be able to tell from a simple finger dip test or a general assessment of the soil if your cactus needs watering.
Watering your cactus shouldn’t be complicated, and it isn’t, but it’s a good idea to be mindful of all the factors that can influence how much water your cactus needs.
Most of these factors are the same for all houseplants, so learning about these now will prepare you to take better care of other houseplants as well.
Cactus plants don’t require you to adhere to a strict watering schedule, nor do they need you to continuously monitor them.
Of all the things you can do wrong when it comes to watering a cactus plant, overwatering is by far the worst.Therefore, keep an eye on the soil and if it’s moist, you can rest assured, your cactus doesn’t need watering.