Barrel Cactus Growth

Soil and Spacing

• A barrel cactus needs moderately rich, well-drained soil that resembles the soil in its arid, native habitat. Allow enough space for the width of your particular barrel cactus variety. If you grow the cactus in a container, fill the container with a commercially prepared cactus-growing mix, or prepare your own mix. A homemade mix can be made by combining one part peat-based potting soil with one part coarse sand or grit, according to Clemson Cooperative Extension. The container should have drainage holes and should be slightly larger than the barrel cactus' root ball.

Sunlight and Water

• Because a barrel cactus grows naturally in arid regions, it performs best when it receives full-sun exposure. Before winter in a freeze-prone region, move a container-grown cactus to a sunny, indoor room where the temperature stays 45 to 55 degrees Fahrenheit. Although rainfall usually provides enough water for a barrel cactus that grows in the ground, the top 3 inches of its soil should be watered during summer droughts every one or two weeks or after the soil dries. Allow the soil in a container-grown cactus to dry slightly between each watering. During winter dormancy, a barrel cactus needs light watering only after its soil completely dries, or every three or four weeks.

Fertilizer

• A barrel cactus that grows in the ground generally does not need additional fertilizer, according to Arizona Cooperative Extension. A container-grown barrel cactus, however, can be fertilized with low-nitrogen, water-soluble cactus fertilizer during the growing season. Mix 1 teaspoon of a commercially prepared, 1-7-6 cactus fertilizer with 1 gallon of water, and use the solution to drench the soil at the base of the container-grown cactus every two weeks in spring and summer. A barrel cactus should not be fertilized barrel during winter, which is its dormant period.

Considerations

• A barrel cactus may develop Pythium soft rot if soil presses against its stem or its soil is overwatered. The fungal disease spreads through wounds in a cactus and causes internal rot in its stem, particularly in a golden barrel cactus. Prevent soft rot by press soil over the cactus' roots but not against its stem, and avoid overwatering the plant's soil. Remove by hand tiny aphids and black, 1-inch-long, cactus longhorn beetles that feed on the end of your barrel cactus. A barrel cactus that has grown indoors or in partial shade can develop sunburn when it is moved to a location that receives full sun. Prevent sunburn, which causes yellowing on the cactus' side that formerly grew in shade, by placing the plant so that its side that formerly faced the sun still faces the sun.