Watering the
Mandacaru will help transport the nutrients that it needs from the soil to the rest of the plant. Without enough moisture, the
Mandacaru won't remain healthy or might even become malnourished. Watering should be done when you see some signs that the plant is thirsty. When you're in doubt, you should never overwater as this can be a way to kill them.
The best way to water them is the soak and dry method. When you see that the soil becomes too dry, you should soak them in water until you see that the pot is dripping with water underneath. Then, go for weeks without watering to give the soil a chance to rest.