Succulents, which include cactuses, store moisture in their fat roots, stems and leaves, making them suitable choices for areas where water is scarce or expensive. Succulents are grown outdoors in the ground and in shallow pots that blend into the landscape and become desert dish gardens. They're also widely grown indoors in dishes and pots. Several factors affect how often succulents' soil needs to be watered.
Growth Cycle and Water Needs
No matter where they're grown, succulents typically use less water than other decorative plants. Most succulents need water when they're actively growing, from early spring to early autumn. Their watering needs decline sharply when they are dormant, from late fall to early spring.
Most succulents do not need water on their roots in winter, mirroring the dry season in most arid environments. As a general rule, succulents need water once every week to two weeks when they're actively growing.
Outdoor Succulents in the Ground
In hot summer weather, succulents growing outdoors typically need water weekly. If your succulents look like they have somehow shrunk and resemble raisins, then they need water. Soak their soil well. Large succulents require more water than small plants.
Succulents need more water when they're young than when they're mature and have developed roots. An example is the popular hens and chicks (Sempervivum spp.), a succulent that is perennial in U.S. Department of Agriculture plant hardiness zones 3 through 8. Sporadic watering and dry soil can kill newly planted hens and chicks, but mature plants can get by with less water.
Larger and more established cactuses require water less often than young plants because of their extensive root systems. Water cactuses growing in the ground with a slow but steady drip from a garden hose for two to six hours, depending on the size of the plants. This deep soaking helps them grow evenly and prevents them from becoming water-stressed.
Outdoor Succulents in Containers
Succulents often evolve to survive in shallow, nutrient-poor desert soils. The wide range of complementary shapes, textures and colors of succulents and cactuses make them natural choices for desert dish gardens with low-watering requirements. If the plants grow in dishes or pots, then the water used to irrigate them should run out of their containers' bottom drain holes.
Check the watering needs of succulents in outdoor dishes or pots by poking your finger into their soil. If the top 1 inch of soil feels dry, then water the plants. Give each small succulent 1 tablespoon of water when its soil is dry. If a plant is 3 inches wide or larger, give it 1/4 cup of water.
Tap water is sometimes alkaline, containing dissolved minerals that can build up in the soil or planting mix of potted succulents. Prevent those deposits from building up, especially on unglazed clay pots, by repotting the plants periodically. Do not use water that was treated by a softening system because it contains extra sodium that is not good for plants.
Plant containers' material and sun exposure affect a watering schedule, too. Succulents growing clay pots dry out quickly. Black, plastic pots increase the heat around succulent roots, increasing their need for water. Potted succulents growing in full sun dry out more quickly than those growing in filtered sunlight.
Indoor Succulents in Containers
As with the containers for succulents growing outdoors, each pot or dish for an indoor succulent should have a bottom drainage hole. When you water a potted plant's soil, the water should reach the roots then drain out of the pot. Follow the same water guidelines as for potted succulents growing outdoors: 1 tablespoon to 1/4 cup, depending on plant size, when the soil is dry. The smaller their container, the more frequently succulents need water because they have less potting mix to retain moisture. For example, a succulent in a 2-inch-wide pot may need water every day.
Do not allow containers to sit in water, which can wick upward.
If you keep dormant succulents at room temperature, then water them once every two to three weeks. Water them monthly in a cooler indoor location, such as a porch or garage. Overwatering dormant succulents can cause root rot.