How Often to Water Cactus: Complete Guide to Watering a Cactus

Cacti plants, like any other succulent plants, do not need frequent watering. They have unique features that aid in storage and conversation of water for dry seasons. So how often should you water your cacti plants?

How often to water your cacti plants depends on several factors. The factors include the size of the plant, the season, growing medium (potted or outdoor), temperature and humidity. There is no definite time when or after how long to water cacti plants. So, water your plants when the soil dries to the roots. You can choose a pattern that works for your outdoor cactus plants.

Cacti plants are easy to manage. However, a wrong watering regime can lead to disastrous damages, such as drying up and rotting up. So, do not be over-enthusiastic when watering your cacti plants or underestimate their water needs.

How many times do you have to water a cactus?

Cactus are tough succulent plants and do not require frequent watering. There is no definite time on when or how many times you should water your cacti plants. So, only water your cactus when the soil is dry to roots.

In the early stages of growth, water your cacti plants at least once a week and give them a good soaking. Potted cacti plants need more watering than those growing in the ground. This is because of the limiting growing conditions, and their extensive roots cannot grow beyond the walls of the planter.

Here are some of the factors that determine how often you should water your cacti plants:

  • Season: when days become longer and warmer, the rate of evapotranspiration increases. So, in such seasons cactus needs frequent watering.
  • Size of the cactus: there is a misconception that large cactus need frequent watering, unlike small ones. However, it is vice versa. The surface area to volume ratio gets small as the tree grows, reducing the rate of evaporation. So, small cactus plants need frequent watering to replace the lost water through evapotranspiration.
  • Growing medium: Potted cactus needs frequent watering, unlike outdoor cactus plants. The extensive roots of an outdoor cactus can draw water from a large area, unlike potted cactus.
  • Humidity: cactus growing in medium or high humid areas do not need frequent watering like those growing in low humidity areas.  
  • Temperature: cactus plants lose water at a high rate in high temperatures. So, water them often to replace the lost water.

Should you water a cactus every day?

No, watering cacti plants every day will lead to waterlogging, which causes root rot disease. Cactus plants can survive under-watering, but overwatering causes significant damages to your plants. Only water your plants when soil is dry to the roots.

How long can you go without watering a cactus?

Cactus are desert plants that can survive without water for up to two years as an outdoor plant. But, indoor cacti cannot survive for that long because of the limiting conditions. Cacti plants have features that aid in water storage and conservation.  During the dry season, the plants use the stored water to survive. The aiding features are:

  • Prickly spines: the prickly spines limits airflow around the cactus leaves, thus reducing water loss through evaporation.
  • Extensive shallow roots: cacti plants have shallow but far-reaching roots that draw water from a large area. Also, when it rains, the root systems soak up with water that the plants use in dry seasons.
  • Fleshy stems: the stems water retention ability, and their shape helps when it comes to water storage. The stems cylindrical or spherical shape reduces surface area to volume ratio, consequently reducing water evaporation rate. The succulent stems soak up with water and store it for a long time for the plants to use in the dry season.

How do you know when a cactus needs water?

Cacti thrive well in dry areas. However, do not underestimate their water needs. The following are some of the signs you can use to tell if your cacti plants are dehydrated:

  • Dry soil to the roots: when the soil dries out completely, that means your cactus plants need water. Use a screwdriver to determine if the soil has completely dried out. A screwdriver will penetrate with difficulties in dry soil, unlike in moist soil.  
  • Withering: the stems of a fully hydrated cactus are rigid. When the stems start softening, that is a sign of dehydration, meaning that the plant needs water.
  • Watering regime: this mostly applies to houseplants. Following your watering system in every season, it will help you determine when your cacti plants need water.

Can you over water a cactus?

No, you should not over water cacti plants. Overwatering leads to waterlogging, which causes root rot disease and, eventually, death of the plant. Cacti thrives in well-drained soils, and that is why they majorly grow in sandy desert soils. Overwatering your cacti is quite disastrous as it is hard to salvage overwatered cacti plants. So, if potting your cactus, ensure to use a planter with enough draining holes to avoid waterlogging.

What does an overwatered cactus look like?

Overwatering causes root rot disease. An overwatered cactus will have signs of a root rot disease. Root rot disease damages the roots limiting absorption and transportation of nutrients and water to the other parts of the plant. The signs include:

  • Wilting.  
  • The base of the plant turns black.
  • Browning or blackening of the leaves and the stems.

Do you water cactus from the top or bottom?

Bottom watering for indoor cacti plants is more suitable. The growing medium also determines a lot. Suppose you plant your cacti plants in foreign inorganic media such as peat moss or perlite use bottom watering. If your cacti are growing in a medium with natural characteristics such as organic sandy soils, use top watering.

Top watering is the only option for outdoor cacti. Bottom watering prevents the spread of the fungus from the soil to the leaves and also helps in water conservation. Here is how to bottom water your cacti:

  1. Fill a seeding tray or any other flat surface container with fresh water.
  2. Place the planters with the cacti plants in the seeding tray.
  3. Leave it until the soil soaks up, and the topsoil is moist.
  4. Remove the planter from the tray and place it in its position.

References

  1. Cactus and Succulent Society of San Jose:  Cactus and Succulent Care for Beginners
  2. University of Minnesota, Extension Services: Cacti-and-succulents